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• What Is a Case Study? | Definition, Examples & Methods

What Is a Case Study? | Definition, Examples & Methods

Published on May 8, 2019 by Shona McCombes . Revised on November 20, 2023.

A case study is a detailed study of a specific subject, such as a person, group, place, event, organization, or phenomenon. Case studies are commonly used in social, educational, clinical, and business research.

A case study research design usually involves qualitative methods , but quantitative methods are sometimes also used. Case studies are good for describing , comparing, evaluating and understanding different aspects of a research problem .

Table of contents

When to do a case study, step 1: select a case, step 2: build a theoretical framework, step 3: collect your data, step 4: describe and analyze the case, other interesting articles.

A case study is an appropriate research design when you want to gain concrete, contextual, in-depth knowledge about a specific real-world subject. It allows you to explore the key characteristics, meanings, and implications of the case.

Case studies are often a good choice in a thesis or dissertation . They keep your project focused and manageable when you don’t have the time or resources to do large-scale research.

You might use just one complex case study where you explore a single subject in depth, or conduct multiple case studies to compare and illuminate different aspects of your research problem.

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Once you have developed your problem statement and research questions , you should be ready to choose the specific case that you want to focus on. A good case study should have the potential to:

• Provide new or unexpected insights into the subject
• Challenge or complicate existing assumptions and theories
• Propose practical courses of action to resolve a problem
• Open up new directions for future research

TipIf your research is more practical in nature and aims to simultaneously investigate an issue as you solve it, consider conducting action research instead.

Unlike quantitative or experimental research , a strong case study does not require a random or representative sample. In fact, case studies often deliberately focus on unusual, neglected, or outlying cases which may shed new light on the research problem.

Example of an outlying case studyIn the 1960s the town of Roseto, Pennsylvania was discovered to have extremely low rates of heart disease compared to the US average. It became an important case study for understanding previously neglected causes of heart disease.

However, you can also choose a more common or representative case to exemplify a particular category, experience or phenomenon.

Example of a representative case studyIn the 1920s, two sociologists used Muncie, Indiana as a case study of a typical American city that supposedly exemplified the changing culture of the US at the time.

While case studies focus more on concrete details than general theories, they should usually have some connection with theory in the field. This way the case study is not just an isolated description, but is integrated into existing knowledge about the topic. It might aim to:

• Exemplify a theory by showing how it explains the case under investigation
• Expand on a theory by uncovering new concepts and ideas that need to be incorporated
• Challenge a theory by exploring an outlier case that doesn’t fit with established assumptions

To ensure that your analysis of the case has a solid academic grounding, you should conduct a literature review of sources related to the topic and develop a theoretical framework . This means identifying key concepts and theories to guide your analysis and interpretation.

There are many different research methods you can use to collect data on your subject. Case studies tend to focus on qualitative data using methods such as interviews , observations , and analysis of primary and secondary sources (e.g., newspaper articles, photographs, official records). Sometimes a case study will also collect quantitative data.

Example of a mixed methods case studyFor a case study of a wind farm development in a rural area, you could collect quantitative data on employment rates and business revenue, collect qualitative data on local people’s perceptions and experiences, and analyze local and national media coverage of the development.

The aim is to gain as thorough an understanding as possible of the case and its context.

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In writing up the case study, you need to bring together all the relevant aspects to give as complete a picture as possible of the subject.

How you report your findings depends on the type of research you are doing. Some case studies are structured like a standard scientific paper or thesis , with separate sections or chapters for the methods , results and discussion .

Others are written in a more narrative style, aiming to explore the case from various angles and analyze its meanings and implications (for example, by using textual analysis or discourse analysis ).

In all cases, though, make sure to give contextual details about the case, connect it back to the literature and theory, and discuss how it fits into wider patterns or debates.

If you want to know more about statistics , methodology , or research bias , make sure to check out some of our other articles with explanations and examples.

• Normal distribution
• Degrees of freedom
• Null hypothesis
• Discourse analysis
• Control groups
• Mixed methods research
• Non-probability sampling
• Quantitative research
• Ecological validity

Research bias

• Rosenthal effect
• Implicit bias
• Cognitive bias
• Selection bias
• Negativity bias
• Status quo bias

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The Ultimate Guide to Qualitative Research - Part 1: The Basics

• Introduction and overview
• What is qualitative research?
• What is qualitative data?
• Examples of qualitative data
• Qualitative vs. quantitative research
• Mixed methods
• Qualitative research preparation
• Theoretical perspective
• Theoretical framework
• Literature reviews

Research question

• Conceptual framework
• Conceptual vs. theoretical framework

Data collection

• Qualitative research methods
• Focus groups
• Observational research

What is a case study?

Applications for case study research, what is a good case study, process of case study design, benefits and limitations of case studies.

• Ethnographical research
• Ethical considerations
• Confidentiality and privacy
• Power dynamics
• Reflexivity

Case studies

Case studies are essential to qualitative research , offering a lens through which researchers can investigate complex phenomena within their real-life contexts. This chapter explores the concept, purpose, applications, examples, and types of case studies and provides guidance on how to conduct case study research effectively.

Whereas quantitative methods look at phenomena at scale, case study research looks at a concept or phenomenon in considerable detail. While analyzing a single case can help understand one perspective regarding the object of research inquiry, analyzing multiple cases can help obtain a more holistic sense of the topic or issue. Let's provide a basic definition of a case study, then explore its characteristics and role in the qualitative research process.

Definition of a case study

A case study in qualitative research is a strategy of inquiry that involves an in-depth investigation of a phenomenon within its real-world context. It provides researchers with the opportunity to acquire an in-depth understanding of intricate details that might not be as apparent or accessible through other methods of research. The specific case or cases being studied can be a single person, group, or organization – demarcating what constitutes a relevant case worth studying depends on the researcher and their research question .

Among qualitative research methods , a case study relies on multiple sources of evidence, such as documents, artifacts, interviews , or observations , to present a complete and nuanced understanding of the phenomenon under investigation. The objective is to illuminate the readers' understanding of the phenomenon beyond its abstract statistical or theoretical explanations.

Characteristics of case studies

Case studies typically possess a number of distinct characteristics that set them apart from other research methods. These characteristics include a focus on holistic description and explanation, flexibility in the design and data collection methods, reliance on multiple sources of evidence, and emphasis on the context in which the phenomenon occurs.

Furthermore, case studies can often involve a longitudinal examination of the case, meaning they study the case over a period of time. These characteristics allow case studies to yield comprehensive, in-depth, and richly contextualized insights about the phenomenon of interest.

The role of case studies in research

Case studies hold a unique position in the broader landscape of research methods aimed at theory development. They are instrumental when the primary research interest is to gain an intensive, detailed understanding of a phenomenon in its real-life context.

In addition, case studies can serve different purposes within research - they can be used for exploratory, descriptive, or explanatory purposes, depending on the research question and objectives. This flexibility and depth make case studies a valuable tool in the toolkit of qualitative researchers.

Remember, a well-conducted case study can offer a rich, insightful contribution to both academic and practical knowledge through theory development or theory verification, thus enhancing our understanding of complex phenomena in their real-world contexts.

What is the purpose of a case study?

Case study research aims for a more comprehensive understanding of phenomena, requiring various research methods to gather information for qualitative analysis . Ultimately, a case study can allow the researcher to gain insight into a particular object of inquiry and develop a theoretical framework relevant to the research inquiry.

Why use case studies in qualitative research?

Using case studies as a research strategy depends mainly on the nature of the research question and the researcher's access to the data.

Conducting case study research provides a level of detail and contextual richness that other research methods might not offer. They are beneficial when there's a need to understand complex social phenomena within their natural contexts.

The explanatory, exploratory, and descriptive roles of case studies

Case studies can take on various roles depending on the research objectives. They can be exploratory when the research aims to discover new phenomena or define new research questions; they are descriptive when the objective is to depict a phenomenon within its context in a detailed manner; and they can be explanatory if the goal is to understand specific relationships within the studied context. Thus, the versatility of case studies allows researchers to approach their topic from different angles, offering multiple ways to uncover and interpret the data .

The impact of case studies on knowledge development

Case studies play a significant role in knowledge development across various disciplines. Analysis of cases provides an avenue for researchers to explore phenomena within their context based on the collected data.

This can result in the production of rich, practical insights that can be instrumental in both theory-building and practice. Case studies allow researchers to delve into the intricacies and complexities of real-life situations, uncovering insights that might otherwise remain hidden.

Types of case studies

In qualitative research , a case study is not a one-size-fits-all approach. Depending on the nature of the research question and the specific objectives of the study, researchers might choose to use different types of case studies. These types differ in their focus, methodology, and the level of detail they provide about the phenomenon under investigation.

Understanding these types is crucial for selecting the most appropriate approach for your research project and effectively achieving your research goals. Let's briefly look at the main types of case studies.

Exploratory case studies

Exploratory case studies are typically conducted to develop a theory or framework around an understudied phenomenon. They can also serve as a precursor to a larger-scale research project. Exploratory case studies are useful when a researcher wants to identify the key issues or questions which can spur more extensive study or be used to develop propositions for further research. These case studies are characterized by flexibility, allowing researchers to explore various aspects of a phenomenon as they emerge, which can also form the foundation for subsequent studies.

Descriptive case studies

Descriptive case studies aim to provide a complete and accurate representation of a phenomenon or event within its context. These case studies are often based on an established theoretical framework, which guides how data is collected and analyzed. The researcher is concerned with describing the phenomenon in detail, as it occurs naturally, without trying to influence or manipulate it.

Explanatory case studies

Explanatory case studies are focused on explanation - they seek to clarify how or why certain phenomena occur. Often used in complex, real-life situations, they can be particularly valuable in clarifying causal relationships among concepts and understanding the interplay between different factors within a specific context.

Intrinsic, instrumental, and collective case studies

These three categories of case studies focus on the nature and purpose of the study. An intrinsic case study is conducted when a researcher has an inherent interest in the case itself. Instrumental case studies are employed when the case is used to provide insight into a particular issue or phenomenon. A collective case study, on the other hand, involves studying multiple cases simultaneously to investigate some general phenomena.

Each type of case study serves a different purpose and has its own strengths and challenges. The selection of the type should be guided by the research question and objectives, as well as the context and constraints of the research.

The flexibility, depth, and contextual richness offered by case studies make this approach an excellent research method for various fields of study. They enable researchers to investigate real-world phenomena within their specific contexts, capturing nuances that other research methods might miss. Across numerous fields, case studies provide valuable insights into complex issues.

Critical information systems research

Case studies provide a detailed understanding of the role and impact of information systems in different contexts. They offer a platform to explore how information systems are designed, implemented, and used and how they interact with various social, economic, and political factors. Case studies in this field often focus on examining the intricate relationship between technology, organizational processes, and user behavior, helping to uncover insights that can inform better system design and implementation.

Health research

Health research is another field where case studies are highly valuable. They offer a way to explore patient experiences, healthcare delivery processes, and the impact of various interventions in a real-world context.

Case studies can provide a deep understanding of a patient's journey, giving insights into the intricacies of disease progression, treatment effects, and the psychosocial aspects of health and illness.

Asthma research studies

Specifically within medical research, studies on asthma often employ case studies to explore the individual and environmental factors that influence asthma development, management, and outcomes. A case study can provide rich, detailed data about individual patients' experiences, from the triggers and symptoms they experience to the effectiveness of various management strategies. This can be crucial for developing patient-centered asthma care approaches.

Other fields

Apart from the fields mentioned, case studies are also extensively used in business and management research, education research, and political sciences, among many others. They provide an opportunity to delve into the intricacies of real-world situations, allowing for a comprehensive understanding of various phenomena.

Case studies, with their depth and contextual focus, offer unique insights across these varied fields. They allow researchers to illuminate the complexities of real-life situations, contributing to both theory and practice.

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Understanding the key elements of case study design is crucial for conducting rigorous and impactful case study research. A well-structured design guides the researcher through the process, ensuring that the study is methodologically sound and its findings are reliable and valid. The main elements of case study design include the research question , propositions, units of analysis, and the logic linking the data to the propositions.

The research question is the foundation of any research study. A good research question guides the direction of the study and informs the selection of the case, the methods of collecting data, and the analysis techniques. A well-formulated research question in case study research is typically clear, focused, and complex enough to merit further detailed examination of the relevant case(s).

Propositions

Propositions, though not necessary in every case study, provide a direction by stating what we might expect to find in the data collected. They guide how data is collected and analyzed by helping researchers focus on specific aspects of the case. They are particularly important in explanatory case studies, which seek to understand the relationships among concepts within the studied phenomenon.

Units of analysis

The unit of analysis refers to the case, or the main entity or entities that are being analyzed in the study. In case study research, the unit of analysis can be an individual, a group, an organization, a decision, an event, or even a time period. It's crucial to clearly define the unit of analysis, as it shapes the qualitative data analysis process by allowing the researcher to analyze a particular case and synthesize analysis across multiple case studies to draw conclusions.

Argumentation

This refers to the inferential model that allows researchers to draw conclusions from the data. The researcher needs to ensure that there is a clear link between the data, the propositions (if any), and the conclusions drawn. This argumentation is what enables the researcher to make valid and credible inferences about the phenomenon under study.

Understanding and carefully considering these elements in the design phase of a case study can significantly enhance the quality of the research. It can help ensure that the study is methodologically sound and its findings contribute meaningful insights about the case.

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Conducting a case study involves several steps, from defining the research question and selecting the case to collecting and analyzing data . This section outlines these key stages, providing a practical guide on how to conduct case study research.

Defining the research question

The first step in case study research is defining a clear, focused research question. This question should guide the entire research process, from case selection to analysis. It's crucial to ensure that the research question is suitable for a case study approach. Typically, such questions are exploratory or descriptive in nature and focus on understanding a phenomenon within its real-life context.

Selecting and defining the case

The selection of the case should be based on the research question and the objectives of the study. It involves choosing a unique example or a set of examples that provide rich, in-depth data about the phenomenon under investigation. After selecting the case, it's crucial to define it clearly, setting the boundaries of the case, including the time period and the specific context.

Previous research can help guide the case study design. When considering a case study, an example of a case could be taken from previous case study research and used to define cases in a new research inquiry. Considering recently published examples can help understand how to select and define cases effectively.

Developing a detailed case study protocol

A case study protocol outlines the procedures and general rules to be followed during the case study. This includes the data collection methods to be used, the sources of data, and the procedures for analysis. Having a detailed case study protocol ensures consistency and reliability in the study.

The protocol should also consider how to work with the people involved in the research context to grant the research team access to collecting data. As mentioned in previous sections of this guide, establishing rapport is an essential component of qualitative research as it shapes the overall potential for collecting and analyzing data.

Collecting data

Gathering data in case study research often involves multiple sources of evidence, including documents, archival records, interviews, observations, and physical artifacts. This allows for a comprehensive understanding of the case. The process for gathering data should be systematic and carefully documented to ensure the reliability and validity of the study.

Analyzing and interpreting data

The next step is analyzing the data. This involves organizing the data , categorizing it into themes or patterns , and interpreting these patterns to answer the research question. The analysis might also involve comparing the findings with prior research or theoretical propositions.

Writing the case study report

The final step is writing the case study report . This should provide a detailed description of the case, the data, the analysis process, and the findings. The report should be clear, organized, and carefully written to ensure that the reader can understand the case and the conclusions drawn from it.

Each of these steps is crucial in ensuring that the case study research is rigorous, reliable, and provides valuable insights about the case.

The type, depth, and quality of data in your study can significantly influence the validity and utility of the study. In case study research, data is usually collected from multiple sources to provide a comprehensive and nuanced understanding of the case. This section will outline the various methods of collecting data used in case study research and discuss considerations for ensuring the quality of the data.

Interviews are a common method of gathering data in case study research. They can provide rich, in-depth data about the perspectives, experiences, and interpretations of the individuals involved in the case. Interviews can be structured , semi-structured , or unstructured , depending on the research question and the degree of flexibility needed.

Observations

Observations involve the researcher observing the case in its natural setting, providing first-hand information about the case and its context. Observations can provide data that might not be revealed in interviews or documents, such as non-verbal cues or contextual information.

Documents and artifacts

Documents and archival records provide a valuable source of data in case study research. They can include reports, letters, memos, meeting minutes, email correspondence, and various public and private documents related to the case.

These records can provide historical context, corroborate evidence from other sources, and offer insights into the case that might not be apparent from interviews or observations.

Physical artifacts refer to any physical evidence related to the case, such as tools, products, or physical environments. These artifacts can provide tangible insights into the case, complementing the data gathered from other sources.

Ensuring the quality of data collection

Determining the quality of data in case study research requires careful planning and execution. It's crucial to ensure that the data is reliable, accurate, and relevant to the research question. This involves selecting appropriate methods of collecting data, properly training interviewers or observers, and systematically recording and storing the data. It also includes considering ethical issues related to collecting and handling data, such as obtaining informed consent and ensuring the privacy and confidentiality of the participants.

Data analysis

Analyzing case study research involves making sense of the rich, detailed data to answer the research question. This process can be challenging due to the volume and complexity of case study data. However, a systematic and rigorous approach to analysis can ensure that the findings are credible and meaningful. This section outlines the main steps and considerations in analyzing data in case study research.

Organizing the data

The first step in the analysis is organizing the data. This involves sorting the data into manageable sections, often according to the data source or the theme. This step can also involve transcribing interviews, digitizing physical artifacts, or organizing observational data.

Categorizing and coding the data

Once the data is organized, the next step is to categorize or code the data. This involves identifying common themes, patterns, or concepts in the data and assigning codes to relevant data segments. Coding can be done manually or with the help of software tools, and in either case, qualitative analysis software can greatly facilitate the entire coding process. Coding helps to reduce the data to a set of themes or categories that can be more easily analyzed.

Identifying patterns and themes

After coding the data, the researcher looks for patterns or themes in the coded data. This involves comparing and contrasting the codes and looking for relationships or patterns among them. The identified patterns and themes should help answer the research question.

Interpreting the data

Once patterns and themes have been identified, the next step is to interpret these findings. This involves explaining what the patterns or themes mean in the context of the research question and the case. This interpretation should be grounded in the data, but it can also involve drawing on theoretical concepts or prior research.

Verification of the data

The last step in the analysis is verification. This involves checking the accuracy and consistency of the analysis process and confirming that the findings are supported by the data. This can involve re-checking the original data, checking the consistency of codes, or seeking feedback from research participants or peers.

Like any research method , case study research has its strengths and limitations. Researchers must be aware of these, as they can influence the design, conduct, and interpretation of the study.

Understanding the strengths and limitations of case study research can also guide researchers in deciding whether this approach is suitable for their research question . This section outlines some of the key strengths and limitations of case study research.

Benefits include the following:

• Rich, detailed data: One of the main strengths of case study research is that it can generate rich, detailed data about the case. This can provide a deep understanding of the case and its context, which can be valuable in exploring complex phenomena.
• Flexibility: Case study research is flexible in terms of design , data collection , and analysis . A sufficient degree of flexibility allows the researcher to adapt the study according to the case and the emerging findings.
• Real-world context: Case study research involves studying the case in its real-world context, which can provide valuable insights into the interplay between the case and its context.
• Multiple sources of evidence: Case study research often involves collecting data from multiple sources , which can enhance the robustness and validity of the findings.

On the other hand, researchers should consider the following limitations:

• Generalizability: A common criticism of case study research is that its findings might not be generalizable to other cases due to the specificity and uniqueness of each case.
• Time and resource intensive: Case study research can be time and resource intensive due to the depth of the investigation and the amount of collected data.
• Complexity of analysis: The rich, detailed data generated in case study research can make analyzing the data challenging.
• Subjectivity: Given the nature of case study research, there may be a higher degree of subjectivity in interpreting the data , so researchers need to reflect on this and transparently convey to audiences how the research was conducted.

Being aware of these strengths and limitations can help researchers design and conduct case study research effectively and interpret and report the findings appropriately.

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What Is a Case Study?

Weighing the pros and cons of this method of research

Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

Cara Lustik is a fact-checker and copywriter.

Verywell / Colleen Tighe

• Pros and Cons

What Types of Case Studies Are Out There?

Where do you find data for a case study, how do i write a psychology case study.

A case study is an in-depth study of one person, group, or event. In a case study, nearly every aspect of the subject's life and history is analyzed to seek patterns and causes of behavior. Case studies can be used in many different fields, including psychology, medicine, education, anthropology, political science, and social work.

The point of a case study is to learn as much as possible about an individual or group so that the information can be generalized to many others. Unfortunately, case studies tend to be highly subjective, and it is sometimes difficult to generalize results to a larger population.

While case studies focus on a single individual or group, they follow a format similar to other types of psychology writing. If you are writing a case study, we got you—here are some rules of APA format to reference.  

At a Glance

A case study, or an in-depth study of a person, group, or event, can be a useful research tool when used wisely. In many cases, case studies are best used in situations where it would be difficult or impossible for you to conduct an experiment. They are helpful for looking at unique situations and allow researchers to gather a lot of˜ information about a specific individual or group of people. However, it's important to be cautious of any bias we draw from them as they are highly subjective.

What Are the Benefits and Limitations of Case Studies?

A case study can have its strengths and weaknesses. Researchers must consider these pros and cons before deciding if this type of study is appropriate for their needs.

One of the greatest advantages of a case study is that it allows researchers to investigate things that are often difficult or impossible to replicate in a lab. Some other benefits of a case study:

• Allows researchers to capture information on the 'how,' 'what,' and 'why,' of something that's implemented
• Gives researchers the chance to collect information on why one strategy might be chosen over another
• Permits researchers to develop hypotheses that can be explored in experimental research

On the other hand, a case study can have some drawbacks:

• It cannot necessarily be generalized to the larger population
• Cannot demonstrate cause and effect
• It may not be scientifically rigorous
• It can lead to bias

Researchers may choose to perform a case study if they want to explore a unique or recently discovered phenomenon. Through their insights, researchers develop additional ideas and study questions that might be explored in future studies.

It's important to remember that the insights from case studies cannot be used to determine cause-and-effect relationships between variables. However, case studies may be used to develop hypotheses that can then be addressed in experimental research.

Case Study Examples

There have been a number of notable case studies in the history of psychology. Much of  Freud's work and theories were developed through individual case studies. Some great examples of case studies in psychology include:

• Anna O : Anna O. was a pseudonym of a woman named Bertha Pappenheim, a patient of a physician named Josef Breuer. While she was never a patient of Freud's, Freud and Breuer discussed her case extensively. The woman was experiencing symptoms of a condition that was then known as hysteria and found that talking about her problems helped relieve her symptoms. Her case played an important part in the development of talk therapy as an approach to mental health treatment.
• Phineas Gage : Phineas Gage was a railroad employee who experienced a terrible accident in which an explosion sent a metal rod through his skull, damaging important portions of his brain. Gage recovered from his accident but was left with serious changes in both personality and behavior.
• Genie : Genie was a young girl subjected to horrific abuse and isolation. The case study of Genie allowed researchers to study whether language learning was possible, even after missing critical periods for language development. Her case also served as an example of how scientific research may interfere with treatment and lead to further abuse of vulnerable individuals.

Such cases demonstrate how case research can be used to study things that researchers could not replicate in experimental settings. In Genie's case, her horrific abuse denied her the opportunity to learn a language at critical points in her development.

This is clearly not something researchers could ethically replicate, but conducting a case study on Genie allowed researchers to study phenomena that are otherwise impossible to reproduce.

There are a few different types of case studies that psychologists and other researchers might use:

• Collective case studies : These involve studying a group of individuals. Researchers might study a group of people in a certain setting or look at an entire community. For example, psychologists might explore how access to resources in a community has affected the collective mental well-being of those who live there.
• Descriptive case studies : These involve starting with a descriptive theory. The subjects are then observed, and the information gathered is compared to the pre-existing theory.
• Explanatory case studies : These   are often used to do causal investigations. In other words, researchers are interested in looking at factors that may have caused certain things to occur.
• Exploratory case studies : These are sometimes used as a prelude to further, more in-depth research. This allows researchers to gather more information before developing their research questions and hypotheses .
• Instrumental case studies : These occur when the individual or group allows researchers to understand more than what is initially obvious to observers.
• Intrinsic case studies : This type of case study is when the researcher has a personal interest in the case. Jean Piaget's observations of his own children are good examples of how an intrinsic case study can contribute to the development of a psychological theory.

The three main case study types often used are intrinsic, instrumental, and collective. Intrinsic case studies are useful for learning about unique cases. Instrumental case studies help look at an individual to learn more about a broader issue. A collective case study can be useful for looking at several cases simultaneously.

The type of case study that psychology researchers use depends on the unique characteristics of the situation and the case itself.

There are a number of different sources and methods that researchers can use to gather information about an individual or group. Six major sources that have been identified by researchers are:

• Archival records : Census records, survey records, and name lists are examples of archival records.
• Direct observation : This strategy involves observing the subject, often in a natural setting . While an individual observer is sometimes used, it is more common to utilize a group of observers.
• Documents : Letters, newspaper articles, administrative records, etc., are the types of documents often used as sources.
• Interviews : Interviews are one of the most important methods for gathering information in case studies. An interview can involve structured survey questions or more open-ended questions.
• Participant observation : When the researcher serves as a participant in events and observes the actions and outcomes, it is called participant observation.
• Physical artifacts : Tools, objects, instruments, and other artifacts are often observed during a direct observation of the subject.

If you have been directed to write a case study for a psychology course, be sure to check with your instructor for any specific guidelines you need to follow. If you are writing your case study for a professional publication, check with the publisher for their specific guidelines for submitting a case study.

Here is a general outline of what should be included in a case study.

Section 1: A Case History

This section will have the following structure and content:

Background information : The first section of your paper will present your client's background. Include factors such as age, gender, work, health status, family mental health history, family and social relationships, drug and alcohol history, life difficulties, goals, and coping skills and weaknesses.

Description of the presenting problem : In the next section of your case study, you will describe the problem or symptoms that the client presented with.

Describe any physical, emotional, or sensory symptoms reported by the client. Thoughts, feelings, and perceptions related to the symptoms should also be noted. Any screening or diagnostic assessments that are used should also be described in detail and all scores reported.

Your diagnosis : Provide your diagnosis and give the appropriate Diagnostic and Statistical Manual code. Explain how you reached your diagnosis, how the client's symptoms fit the diagnostic criteria for the disorder(s), or any possible difficulties in reaching a diagnosis.

Section 2: Treatment Plan

This portion of the paper will address the chosen treatment for the condition. This might also include the theoretical basis for the chosen treatment or any other evidence that might exist to support why this approach was chosen.

• Cognitive behavioral approach : Explain how a cognitive behavioral therapist would approach treatment. Offer background information on cognitive behavioral therapy and describe the treatment sessions, client response, and outcome of this type of treatment. Make note of any difficulties or successes encountered by your client during treatment.
• Humanistic approach : Describe a humanistic approach that could be used to treat your client, such as client-centered therapy . Provide information on the type of treatment you chose, the client's reaction to the treatment, and the end result of this approach. Explain why the treatment was successful or unsuccessful.
• Psychoanalytic approach : Describe how a psychoanalytic therapist would view the client's problem. Provide some background on the psychoanalytic approach and cite relevant references. Explain how psychoanalytic therapy would be used to treat the client, how the client would respond to therapy, and the effectiveness of this treatment approach.
• Pharmacological approach : If treatment primarily involves the use of medications, explain which medications were used and why. Provide background on the effectiveness of these medications and how monotherapy may compare with an approach that combines medications with therapy or other treatments.

This section of a case study should also include information about the treatment goals, process, and outcomes.

When you are writing a case study, you should also include a section where you discuss the case study itself, including the strengths and limitiations of the study. You should note how the findings of your case study might support previous research. 

In your discussion section, you should also describe some of the implications of your case study. What ideas or findings might require further exploration? How might researchers go about exploring some of these questions in additional studies?

Need More Tips?

Here are a few additional pointers to keep in mind when formatting your case study:

• Never refer to the subject of your case study as "the client." Instead, use their name or a pseudonym.
• Read examples of case studies to gain an idea about the style and format.
• Remember to use APA format when citing references .

Crowe S, Cresswell K, Robertson A, Huby G, Avery A, Sheikh A. The case study approach .  BMC Med Res Methodol . 2011;11:100.

Crowe S, Cresswell K, Robertson A, Huby G, Avery A, Sheikh A. The case study approach . BMC Med Res Methodol . 2011 Jun 27;11:100. doi:10.1186/1471-2288-11-100

Gagnon, Yves-Chantal.  The Case Study as Research Method: A Practical Handbook . Canada, Chicago Review Press Incorporated DBA Independent Pub Group, 2010.

Yin, Robert K. Case Study Research and Applications: Design and Methods . United States, SAGE Publications, 2017.

By Kendra Cherry, MSEd Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

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• Case Study | Definition, Examples & Methods

Case Study | Definition, Examples & Methods

Published on 5 May 2022 by Shona McCombes . Revised on 30 January 2023.

A case study is a detailed study of a specific subject, such as a person, group, place, event, organisation, or phenomenon. Case studies are commonly used in social, educational, clinical, and business research.

A case study research design usually involves qualitative methods , but quantitative methods are sometimes also used. Case studies are good for describing , comparing, evaluating, and understanding different aspects of a research problem .

Table of contents

When to do a case study, step 1: select a case, step 2: build a theoretical framework, step 3: collect your data, step 4: describe and analyse the case.

A case study is an appropriate research design when you want to gain concrete, contextual, in-depth knowledge about a specific real-world subject. It allows you to explore the key characteristics, meanings, and implications of the case.

Case studies are often a good choice in a thesis or dissertation . They keep your project focused and manageable when you don’t have the time or resources to do large-scale research.

You might use just one complex case study where you explore a single subject in depth, or conduct multiple case studies to compare and illuminate different aspects of your research problem.

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Once you have developed your problem statement and research questions , you should be ready to choose the specific case that you want to focus on. A good case study should have the potential to:

• Provide new or unexpected insights into the subject
• Challenge or complicate existing assumptions and theories
• Propose practical courses of action to resolve a problem
• Open up new directions for future research

Unlike quantitative or experimental research, a strong case study does not require a random or representative sample. In fact, case studies often deliberately focus on unusual, neglected, or outlying cases which may shed new light on the research problem.

If you find yourself aiming to simultaneously investigate and solve an issue, consider conducting action research . As its name suggests, action research conducts research and takes action at the same time, and is highly iterative and flexible. 

However, you can also choose a more common or representative case to exemplify a particular category, experience, or phenomenon.

While case studies focus more on concrete details than general theories, they should usually have some connection with theory in the field. This way the case study is not just an isolated description, but is integrated into existing knowledge about the topic. It might aim to:

• Exemplify a theory by showing how it explains the case under investigation
• Expand on a theory by uncovering new concepts and ideas that need to be incorporated
• Challenge a theory by exploring an outlier case that doesn’t fit with established assumptions

To ensure that your analysis of the case has a solid academic grounding, you should conduct a literature review of sources related to the topic and develop a theoretical framework . This means identifying key concepts and theories to guide your analysis and interpretation.

There are many different research methods you can use to collect data on your subject. Case studies tend to focus on qualitative data using methods such as interviews, observations, and analysis of primary and secondary sources (e.g., newspaper articles, photographs, official records). Sometimes a case study will also collect quantitative data .

The aim is to gain as thorough an understanding as possible of the case and its context.

In writing up the case study, you need to bring together all the relevant aspects to give as complete a picture as possible of the subject.

How you report your findings depends on the type of research you are doing. Some case studies are structured like a standard scientific paper or thesis, with separate sections or chapters for the methods , results , and discussion .

Others are written in a more narrative style, aiming to explore the case from various angles and analyse its meanings and implications (for example, by using textual analysis or discourse analysis ).

In all cases, though, make sure to give contextual details about the case, connect it back to the literature and theory, and discuss how it fits into wider patterns or debates.

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How to Write a Case Study: The Compelling Step-by-Step Guide

Is there a poignant pain point that needs to be addressed in your company or industry? Do you have a possible solution but want to test your theory? Why not turn this drive into a transformative learning experience and an opportunity to produce a high-quality business case study? However, before that occurs, you may wonder how to write a case study.

You may also be thinking about why you should produce one at all. Did you know that case studies are impactful and the fifth most used type of content in marketing , despite being more resource-intensive to produce?

Below, we’ll delve into what a case study is, its benefits, and how to approach business case study writing:

Definition of a Written case study and its Purpose

A case study is a research method that involves a detailed and comprehensive examination of a specific real-life situation. It’s often used in various fields, including business, education, economics, and sociology, to understand a complex issue better. 

It typically includes an in-depth analysis of the subject and an examination of its context and background information, incorporating data from multiple sources, such as interviews, observations, and existing literature. 

The ultimate aim is to provide a rich and detailed account of a situation to identify patterns and relationships, generate new insights and understanding, illustrate theories, or test hypotheses.

Importance of Business Case Study Writing

As such an in-depth exploration into a subject with potentially far-reaching consequences, a case study has benefits to offer various stakeholders in the organisation leading it.

• Business Founders: Use business case study writing to highlight real-life examples of companies or individuals who have benefited from their products or services, providing potential customers with a tangible demonstration of the value their business can bring. It can be effective for attracting new clients or investors by showcasing thought leadership and building trust and credibility.
• Marketers through case studies and encourage them to take action: Marketers use a case studies writer to showcase the success of a particular product, service, or marketing campaign. They can use persuasive storytelling to engage the reader, whether it’s consumers, clients, or potential partners.
• Researchers: They allow researchers to gain insight into real-world scenarios, explore a variety of perspectives, and develop a nuanced understanding of the factors that contribute to success or failure. Additionally, case studies provide practical business recommendations and help build a body of knowledge in a particular field.

How to Write a Case Study – The Key Elements 

Considering how to write a case study can seem overwhelming at first. However, looking at it in terms of its constituent parts will help you to get started, focus on the key issue(s), and execute it efficiently and effectively.

Problem or Challenge Statement

A problem statement concisely describes a specific issue or problem that a written case study aims to address. It sets the stage for the rest of the case study and provides context for the reader. 

Here are some steps to help you write a case study problem statement:

• Identify the problem or issue that the case study will focus on.
• Research the problem to better understand its context, causes, and effects.
• Define the problem clearly and concisely. Be specific and avoid generalisations.
• State the significance of the problem: Explain why the issue is worth solving. Consider the impact it has on the individual, organisation, or industry.
• Provide background information that will help the reader understand the context of the problem.
• Keep it concise: A problem statement should be brief and to the point. Avoid going into too much detail – leave this for the body of the case study!

Here is an example of a problem statement for a case study:

“ The XYZ Company is facing a problem with declining sales and increasing customer complaints. Despite improving the customer experience, the company has yet to reverse the trend . This case study will examine the causes of the problem and propose solutions to improve sales and customer satisfaction. “

Solutions and interventions

Business case study writing provides a solution or intervention that identifies the best course of action to address the problem or issue described in the problem statement. 

Here are some steps to help you write a case study solution or intervention:

• Identify the objective , which should be directly related to the problem statement.
• Analyse the data, which could include data from interviews, observations, and existing literature.
• Evaluate alternatives that have been proposed or implemented in similar situations, considering their strengths, weaknesses, and impact.
• Choose the best solution based on the objective and data analysis. Remember to consider factors such as feasibility, cost, and potential impact.
• Justify the solution by explaining how it addresses the problem and why it’s the best solution with supportive evidence.
• Provide a detailed, step-by-step plan of action that considers the resources required, timeline, and expected outcomes.

Example of a solution or intervention for a case study:

“ To address the problem of declining sales and increasing customer complaints at the XYZ Company, we propose a comprehensive customer experience improvement program. “

“ This program will involve the following steps:

• Conducting customer surveys to gather feedback and identify areas for improvement
• Implementing training programs for employees to improve customer service skills
• Revising the company’s product offerings to meet customer needs better
• Implementing a customer loyalty program to encourage repeat business “

“ These steps will improve customer satisfaction and increase sales. We expect a 10% increase in sales within the first year of implementation, based on similar programs implemented by other companies in the industry. “

Possible Results and outcomes

Writing case study results and outcomes involves presenting the impact of the proposed solution or intervention. 

Here are some steps to help you write case study results and outcomes:

• Evaluate the solution by measuring its effectiveness in addressing the problem statement. That could involve collecting data, conducting surveys, or monitoring key performance indicators.
• Present the results clearly and concisely, using graphs, charts, and tables to represent the data where applicable visually. Be sure to include both quantitative and qualitative results.
• Compare the results to the expectations set in the solution or intervention section. Explain any discrepancies and why they occurred.
• Discuss the outcomes and impact of the solution, considering the benefits and drawbacks and what lessons can be learned.
• Provide recommendations for future action based on the results. For example, what changes should be made to improve the solution, or what additional steps should be taken?

Example of results and outcomes for a case study:

“ The customer experience improvement program implemented at the XYZ Company was successful. We found significant improvement in employee health and productivity. The program, which included on-site exercise classes and healthy food options, led to a 25% decrease in employee absenteeism and a 15% increase in productivity . “

“ Employee satisfaction with the program was high, with 90% reporting an improved work-life balance. Despite initial costs, the program proved to be cost-effective in the long run, with decreased healthcare costs and increased employee retention. The company plans to continue the program and explore expanding it to other offices .”

Case Study Key takeaways

Key takeaways are the most important and relevant insights and lessons that can be drawn from a case study. Key takeaways can help readers understand the most significant outcomes and impacts of the solution or intervention. 

Here are some steps to help you write case study key takeaways:

• Summarise the problem that was addressed and the solution that was proposed.
• Highlight the most significant results from the case study.
• Identify the key insights and lessons , including what makes the case study unique and relevant to others.
• Consider the broader implications of the outcomes for the industry or field.
• Present the key takeaways clearly and concisely , using bullet points or a list format to make the information easy to understand.

Example of key takeaways for a case study:

• The customer experience improvement program at XYZ Company successfully increased customer satisfaction and sales.
• Employee training and product development were critical components of the program’s success.
• The program resulted in a 20% increase in repeat business, demonstrating the value of a customer loyalty program.
• Despite some initial challenges, the program proved cost-effective in the long run.
• The case study results demonstrate the importance of investing in customer experience to improve business outcomes.

Steps for a Case Study Writer to Follow

If you still feel lost, the good news is as a case studies writer; there is a blueprint you can follow to complete your work. It may be helpful at first to proceed step-by-step and let your research and analysis guide the process:

• Select a suitable case study subject: Ask yourself what the purpose of the business case study is. Is it to illustrate a specific problem and solution, showcase a success story, or demonstrate best practices in a particular field? Based on this, you can select a suitable subject by researching and evaluating various options.
• Research and gather information: We have already covered this in detail above. However, always ensure all data is relevant, valid, and comes from credible sources. Research is the crux of your written case study, and you can’t compromise on its quality.
• Develop a clear and concise problem statement: Follow the guide above, and don’t rush to finalise it. It will set the tone and lay the foundation for the entire study.
• Detail the solution or intervention: Follow the steps above to detail your proposed solution or intervention.
• Present the results and outcomes: Remember that a case study is an unbiased test of how effectively a particular solution addresses an issue. Not all case studies are meant to end in a resounding success. You can often learn more from a loss than a win.
• Include key takeaways and conclusions: Follow the steps above to detail your proposed business case study solution or intervention.

Tips for How to Write a Case Study

Here are some bonus tips for how to write a case study. These tips will help improve the quality of your work and the impact it will have on readers:

• Use a storytelling format: Just because a case study is research-based doesn’t mean it has to be boring and detached. Telling a story will engage readers and help them better identify with the problem statement and see the value in the outcomes. Framing it as a narrative in a real-world context will make it more relatable and memorable.
• Include quotes and testimonials from stakeholders: This will add credibility and depth to your written case study. It also helps improve engagement and will give your written work an emotional impact.
• Use visuals and graphics to support your narrative: Humans are better at processing visually presented data than endless walls of black-on-white text. Visual aids will make it easier to grasp key concepts and make your case study more engaging and enjoyable. It breaks up the text and allows readers to identify key findings and highlights quickly.
• Edit and revise your case study for clarity and impact: As a long and involved project, it can be easy to lose your narrative while in the midst of it. Multiple rounds of editing are vital to ensure your narrative holds, that your message gets across, and that your spelling and grammar are correct, of course!

Our Final Thoughts

A written case study can be a powerful tool in your writing arsenal. It’s a great way to showcase your knowledge in a particular business vertical, industry, or situation. Not only is it an effective way to build authority and engage an audience, but also to explore an important problem and the possible solutions to it. It’s a win-win, even if the proposed solution doesn’t have the outcome you expect. So now that you know more about how to write a case study, try it or talk to us for further guidance.

Are you ready to write your own case study?

Begin by bookmarking this article, so you can come back to it. And for more writing advice and support, read our resource guides  and  blog content . If you are unsure, please reach out with questions, and we will provide the answers or assistance you need.

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What the Case Study Method Really Teaches

• Nitin Nohria

Seven meta-skills that stick even if the cases fade from memory.

It’s been 100 years since Harvard Business School began using the case study method. Beyond teaching specific subject matter, the case study method excels in instilling meta-skills in students. This article explains the importance of seven such skills: preparation, discernment, bias recognition, judgement, collaboration, curiosity, and self-confidence.

During my decade as dean of Harvard Business School, I spent hundreds of hours talking with our alumni. To enliven these conversations, I relied on a favorite question: “What was the most important thing you learned from your time in our MBA program?”

• Nitin Nohria is the George F. Baker Jr. Professor at Harvard Business School and the former dean of HBS.

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• Volume 21, Issue 1
• What is a case study?
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• Roberta Heale 1 ,
• Alison Twycross 2
• 1 School of Nursing , Laurentian University , Sudbury , Ontario , Canada
• 2 School of Health and Social Care , London South Bank University , London , UK
• Correspondence to Dr Roberta Heale, School of Nursing, Laurentian University, Sudbury, ON P3E2C6, Canada; rheale{at}laurentian.ca

https://doi.org/10.1136/eb-2017-102845

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What is it?

Case study is a research methodology, typically seen in social and life sciences. There is no one definition of case study research. 1 However, very simply… ‘a case study can be defined as an intensive study about a person, a group of people or a unit, which is aimed to generalize over several units’. 1 A case study has also been described as an intensive, systematic investigation of a single individual, group, community or some other unit in which the researcher examines in-depth data relating to several variables. 2

Often there are several similar cases to consider such as educational or social service programmes that are delivered from a number of locations. Although similar, they are complex and have unique features. In these circumstances, the evaluation of several, similar cases will provide a better answer to a research question than if only one case is examined, hence the multiple-case study. Stake asserts that the cases are grouped and viewed as one entity, called the quintain . 6  ‘We study what is similar and different about the cases to understand the quintain better’. 6

The steps when using case study methodology are the same as for other types of research. 6 The first step is defining the single case or identifying a group of similar cases that can then be incorporated into a multiple-case study. A search to determine what is known about the case(s) is typically conducted. This may include a review of the literature, grey literature, media, reports and more, which serves to establish a basic understanding of the cases and informs the development of research questions. Data in case studies are often, but not exclusively, qualitative in nature. In multiple-case studies, analysis within cases and across cases is conducted. Themes arise from the analyses and assertions about the cases as a whole, or the quintain, emerge. 6

Benefits and limitations of case studies

If a researcher wants to study a specific phenomenon arising from a particular entity, then a single-case study is warranted and will allow for a in-depth understanding of the single phenomenon and, as discussed above, would involve collecting several different types of data. This is illustrated in example 1 below.

Using a multiple-case research study allows for a more in-depth understanding of the cases as a unit, through comparison of similarities and differences of the individual cases embedded within the quintain. Evidence arising from multiple-case studies is often stronger and more reliable than from single-case research. Multiple-case studies allow for more comprehensive exploration of research questions and theory development. 6

Despite the advantages of case studies, there are limitations. The sheer volume of data is difficult to organise and data analysis and integration strategies need to be carefully thought through. There is also sometimes a temptation to veer away from the research focus. 2 Reporting of findings from multiple-case research studies is also challenging at times, 1 particularly in relation to the word limits for some journal papers.

Examples of case studies

Example 1: nurses’ paediatric pain management practices.

One of the authors of this paper (AT) has used a case study approach to explore nurses’ paediatric pain management practices. This involved collecting several datasets:

Observational data to gain a picture about actual pain management practices.

Questionnaire data about nurses’ knowledge about paediatric pain management practices and how well they felt they managed pain in children.

Questionnaire data about how critical nurses perceived pain management tasks to be.

These datasets were analysed separately and then compared 7–9 and demonstrated that nurses’ level of theoretical did not impact on the quality of their pain management practices. 7 Nor did individual nurse’s perceptions of how critical a task was effect the likelihood of them carrying out this task in practice. 8 There was also a difference in self-reported and observed practices 9 ; actual (observed) practices did not confirm to best practice guidelines, whereas self-reported practices tended to.

Example 2: quality of care for complex patients at Nurse Practitioner-Led Clinics (NPLCs)

The other author of this paper (RH) has conducted a multiple-case study to determine the quality of care for patients with complex clinical presentations in NPLCs in Ontario, Canada. 10 Five NPLCs served as individual cases that, together, represented the quatrain. Three types of data were collected including:

Review of documentation related to the NPLC model (media, annual reports, research articles, grey literature and regulatory legislation).

Interviews with nurse practitioners (NPs) practising at the five NPLCs to determine their perceptions of the impact of the NPLC model on the quality of care provided to patients with multimorbidity.

Chart audits conducted at the five NPLCs to determine the extent to which evidence-based guidelines were followed for patients with diabetes and at least one other chronic condition.

The three sources of data collected from the five NPLCs were analysed and themes arose related to the quality of care for complex patients at NPLCs. The multiple-case study confirmed that nurse practitioners are the primary care providers at the NPLCs, and this positively impacts the quality of care for patients with multimorbidity. Healthcare policy, such as lack of an increase in salary for NPs for 10 years, has resulted in issues in recruitment and retention of NPs at NPLCs. This, along with insufficient resources in the communities where NPLCs are located and high patient vulnerability at NPLCs, have a negative impact on the quality of care. 10

These examples illustrate how collecting data about a single case or multiple cases helps us to better understand the phenomenon in question. Case study methodology serves to provide a framework for evaluation and analysis of complex issues. It shines a light on the holistic nature of nursing practice and offers a perspective that informs improved patient care.

• Gustafsson J
• Calanzaro M
• Sandelowski M

Competing interests None declared.

Provenance and peer review Commissioned; internally peer reviewed.

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What is a Case Study? [+6 Types of Case Studies]

By Ronita Mohan , Sep 20, 2021

Case studies have become powerful business tools. But what is a case study? What are the benefits of creating one? Are there limitations to the format?

If you’ve asked yourself these questions, our helpful guide will clear things up. Learn how to use a case study for business. Find out how cases analysis works in psychology and research.

We’ve also got examples of case studies to inspire you.

Haven’t made a case study before? You can easily  create a case study  with Venngage’s customizable templates.

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Click to jump ahead:

What is a case study, what is the case study method, benefits of case studies, limitations of case studies, types of case studies, faqs about case studies.

Case studies are research methodologies. They examine subjects, projects, or organizations to tell a story.

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Numerous sectors use case analyses. The social sciences, social work, and psychology create studies regularly.

Healthcare industries write reports on patients and diagnoses. Marketing case study examples , like the one below, highlight the benefits of a business product.

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Now that you know what a case study is, we explain how case reports are used in three different industries.

What is a business case study?

A business or marketing case study aims at showcasing a successful partnership. This can be between a brand and a client. Or the case study can examine a brand’s project.

There is a perception that case studies are used to advertise a brand. But effective reports, like the one below, can show clients how a brand can support them.

Hubspot created a case study on a customer that successfully scaled its business. The report outlines the various Hubspot tools used to achieve these results.

Hubspot also added a video with testimonials from the client company’s employees.

So, what is the purpose of a case study for businesses? There is a lot of competition in the corporate world. Companies are run by people. They can be on the fence about which brand to work with.

Business reports  stand out aesthetically, as well. They use  brand colors  and brand fonts . Usually, a combination of the client’s and the brand’s.

With the Venngage  My Brand Kit  feature, businesses can automatically apply their brand to designs.

A business case study, like the one below, acts as social proof. This helps customers decide between your brand and your competitors.

Don’t know how to design a report? You can learn  how to write a case study  with Venngage’s guide. We also share design tips and examples that will help you convert.

Related: 55+ Annual Report Design Templates, Inspirational Examples & Tips [Updated]

What is a case study in psychology?

In the field of psychology, case studies focus on a particular subject. Psychology case histories also examine human behaviors.

Case reports search for commonalities between humans. They are also used to prescribe further research. Or these studies can elaborate on a solution for a behavioral ailment.

The American Psychology Association  has a number of case studies on real-life clients. Note how the reports are more text-heavy than a business case study.

Famous psychologists such as Sigmund Freud and Anna O popularised the use of case studies in the field. They did so by regularly interviewing subjects. Their detailed observations build the field of psychology.

It is important to note that psychological studies must be conducted by professionals. Psychologists, psychiatrists and therapists should be the researchers in these cases.

Related: What Netflix’s Top 50 Shows Can Teach Us About Font Psychology [Infographic]

What is a case study in research?

Research is a necessary part of every case study. But specific research fields are required to create studies. These fields include user research, healthcare, education, or social work.

For example, this UX Design  report examined the public perception of a client. The brand researched and implemented new visuals to improve it. The study breaks down this research through lessons learned.

Clinical reports are a necessity in the medical field. These documents are used to share knowledge with other professionals. They also help examine new or unusual diseases or symptoms.

The pandemic has led to a significant increase in research. For example,  Spectrum Health  studied the value of health systems in the pandemic. They created the study by examining community outreach.

The pandemic has significantly impacted the field of education. This has led to numerous examinations on remote studying. There have also been studies on how students react to decreased peer communication.

Social work case reports often have a community focus. They can also examine public health responses. In certain regions, social workers study disaster responses.

You now know what case studies in various fields are. In the next step of our guide, we explain the case study method.

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A case analysis is a deep dive into a subject. To facilitate this case studies are built on interviews and observations. The below example would have been created after numerous interviews.

Case studies are largely qualitative. They analyze and describe phenomena. While some data is included, a case analysis is not quantitative.

There are a few steps in the case method. You have to start by identifying the subject of your study. Then determine what kind of research is required.

In natural sciences, case studies can take years to complete. Business reports, like this one, don’t take that long. A few weeks of interviews should be enough.

The case method will vary depending on the industry. Reports will also look different once produced.

As you will have seen, business reports are more colorful. The design is also more accessible . Healthcare and psychology reports are more text-heavy.

Designing case reports takes time and energy. So, is it worth taking the time to write them? Here are the benefits of creating case studies.

• Collects large amounts of information
• Helps formulate hypotheses
• Builds the case for further research
• Discovers new insights into a subject
• Builds brand trust and loyalty
• Engages customers through stories

For example, the business study below creates a story around a brand partnership. It makes for engaging reading. The study also shows evidence backing up the information.

We’ve shared the benefits of why studies are needed. We will also look at the limitations of creating them.

Related: How to Present a Case Study like a Pro (With Examples)

There are a few disadvantages to conducting a case analysis. The limitations will vary according to the industry.

• Responses from interviews are subjective
• Subjects may tailor responses to the researcher
• Studies can’t always be replicated
• In certain industries, analyses can take time and be expensive
• Risk of generalizing the results among a larger population

These are some of the common weaknesses of creating case reports. If you’re on the fence, look at the competition in your industry.

Other brands or professionals are building reports, like this example. In that case, you may want to do the same.

There are six common types of case reports. Depending on your industry, you might use one of these types.

Descriptive case studies

Explanatory case studies, exploratory case reports, intrinsic case studies, instrumental case studies, collective case reports.

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We go into more detail about each type of study in the guide below.

Related:  15+ Professional Case Study Examples [Design Tips + Templates]

When you have an existing hypothesis, you can design a descriptive study. This type of report starts with a description. The aim is to find connections between the subject being studied and a theory.

Once these connections are found, the study can conclude. The results of this type of study will usually suggest how to develop a theory further.

A study like the one below has concrete results. A descriptive report would use the quantitative data as a suggestion for researching the subject deeply.

When an incident occurs in a field, an explanation is required. An explanatory report investigates the cause of the event. It will include explanations for that cause.

The study will also share details about the impact of the event. In most cases, this report will use evidence to predict future occurrences. The results of explanatory reports are definitive.

Note that there is no room for interpretation here. The results are absolute.

The study below is a good example. It explains how one brand used the services of another. It concludes by showing definitive proof that the collaboration was successful.

Another example of this study would be in the automotive industry. If a vehicle fails a test, an explanatory study will examine why. The results could show that the failure was because of a particular part.

Related: How to Write a Case Study [+ Design Tips]

An explanatory report is a self-contained document. An exploratory one is only the beginning of an investigation.

Exploratory cases act as the starting point of studies. This is usually conducted as a precursor to large-scale investigations. The research is used to suggest why further investigations are needed.

An exploratory study can also be used to suggest methods for further examination.

For example, the below analysis could have found inconclusive results. In that situation, it would be the basis for an in-depth study.

Intrinsic studies are more common in the field of psychology. These reports can also be conducted in healthcare or social work.

These types of studies focus on a unique subject, such as a patient. They can sometimes study groups close to the researcher.

The aim of such studies is to understand the subject better. This requires learning their history. The researcher will also examine how they interact with their environment.

For instance, if the case study below was about a unique brand, it could be an intrinsic study.

Once the study is complete, the researcher will have developed a better understanding of a phenomenon. This phenomenon will likely not have been studied or theorized about before.

Examples of intrinsic case analysis can be found across psychology. For example, Jean Piaget’s theories on cognitive development. He established the theory from intrinsic studies into his own children.

Related: What Disney Villains Can Tell Us About Color Psychology [Infographic]

This is another type of study seen in medical and psychology fields. Instrumental reports are created to examine more than just the primary subject.

When research is conducted for an instrumental study, it is to provide the basis for a larger phenomenon. The subject matter is usually the best example of the phenomenon. This is why it is being studied.

Assume it’s examining lead generation strategies. It may want to show that visual marketing is the definitive lead generation tool. The brand can conduct an instrumental case study to examine this phenomenon.

Collective studies are based on instrumental case reports. These types of studies examine multiple reports.

There are a number of reasons why collective reports are created:

• To provide evidence for starting a new study
• To find pattens between multiple instrumental reports
• To find differences in similar types of cases
• Gain a deeper understanding of a complex phenomenon
• Understand a phenomenon from diverse contexts

A researcher could use multiple reports, like the one below, to build a collective case report.

Related: 10+ Case Study Infographic Templates That Convert

What makes a case study a case study?

A case study has a very particular research methodology. They are an in-depth study of a person or a group of individuals. They can also study a community or an organization. Case reports examine real-world phenomena within a set context.

How long should a case study be?

The length of studies depends on the industry. It also depends on the story you’re telling. Most case studies should be at least 500-1500 words long. But you can increase the length if you have more details to share.

What should you ask in a case study?

The one thing you shouldn’t ask is ‘yes’ or ‘no’ questions. Case studies are qualitative. These questions won’t give you the information you need.

Ask your client about the problems they faced. Ask them about solutions they found. Or what they think is the ideal solution. Leave room to ask them follow-up questions. This will help build out the study.

How to present a case study?

When you’re ready to present a case study, begin by providing a summary of the problem or challenge you were addressing. Follow this with an outline of the solution you implemented, and support this with the results you achieved, backed by relevant data. Incorporate visual aids like slides, graphs, and images to make your case study presentation more engaging and impactful.

Now you know what a case study means, you can begin creating one. These reports are a great tool for analyzing brands. They are also useful in a variety of other fields.

Use a visual communication platform like Venngage to design case studies. With Venngage’s templates, you can design easily. Create branded, engaging reports, all without design experience.

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Your Step-By-Step Guide To Writing a Case Study

Creating a case study is both an art and a science. It requires making an in-depth exploration of your chosen subject in order to extract meaningful insights and understand the dynamics that more general surveys or statistical research might not uncover. At the same time, your case study also needs to be a compelling read to ensure those insights get attention from other people!

Unsurprisingly, the prospect of crafting an effective case study can be daunting. It calls for strategic planning, careful organization, and clear communication, all of which can be challenging even for experienced researchers. That's why we've created this step-by-step guide, which breaks the process down into manageable steps, demystifying the journey from defining your research question to sharing your findings. Whether you're a seasoned researcher or a first-timer, this guide aims to equip you with the necessary tools and tips to create a case study that's not just informative, but also engaging and impactful.

Are you ready to unlock the potential of case studies? Let's dive in!

What is a case study?

First, it's important to understand what a case study is – and what it isn't.

A case study is a thorough exploration of a specific subject or event over a certain time frame. Case studies are utilized in numerous fields, including sociology, psychology, education, anthropology, business, and the health sciences, and employ various research techniques to shed light on complex issues.

A case study does not provide absolute proof or conclusions that can be universally applied. Because it concentrates on one particular case or just a few cases, the findings might not apply to different contexts or subjects. Case studies also aren't ideal for determining cause-and-effect relationships as they do not use controlled conditions to separate and measure the impacts of different factors. Lastly, it must be said that a case study isn't just a random assortment of facts or observations; it necessitates a clear research question, a methodical approach to data collection and analysis, and a thoughtful interpretation of the results.

Getting started

Now that we've established the definition and purpose of a case study, let's explore the process by which one is created. You can produce a case study by following these nine steps:

1. Define the purpose of your case study

Before you start writing a case study, you need to define its purpose clearly. Ask yourself: What is the research question or problem you aim to solve? What insights are you looking to uncover? Your goals will guide your research design and influence your choice of case. This initial stage of introspection and clarification is crucial as it acts as a roadmap for your study.

2. Select the case to study

Once you've defined your research objective, the next step is to choose a suitable case that can help answer your research question. This might be a unique, critical, or representative instance. Unique cases offer the opportunity to observe and analyze a situation that is unusual or not well-understood. In contrast, a representative or typical case is often chosen because it represents other cases or a broader phenomenon.

In any case, be sure to justify your choice. Explain why the case is of interest and how it can contribute to the knowledge or understanding of the issue at hand. For instance, if you're studying the effects of corporate restructuring on employee morale, you might choose to focus on a company that recently underwent a significant restructure.

3. Conduct a thorough literature review

Performing a literature review involves a careful examination of relevant scholarly articles, books, and other sources related to your research question or problem. In the process, you identify gaps in the current knowledge and determine how your case study can address them. By critically examining existing research, you will not only gain a comprehensive understanding of your chosen topic but also be able to refine your research question or hypothesis, if necessary.

4. Choose a methodological approach

The methodological approach used in your case study will depend on your research objectives and the nature of the case. Methodologies that can be employed in case studies include qualitative, quantitative, and mixed methods .

Qualitative methods are often used when the goal is to explore, understand, or interpret certain phenomena. These involve approaches like interviews, focus groups, or ethnography. Quantitative methods, on the other hand, are used when the goal is to test hypotheses or examine relationships between variables. Quantitative approaches often include experiments. Also, surveys may be either qualitative or quantitative depending on the question design.

You may choose to use a combination of qualitative and quantitative methods (mixed methods) if it suits your research objectives.

5. Collect and organize your data

Data collection should be systematic and organized to maintain the integrity and reliability of your research. You need to plan how you will record and store your data to ensure that it's accessible and usable.

If you're conducting interviews or observations, consider using recording devices (with participant consent) to capture the data accurately. In addition, you may want to transcribe the recorded material for easier analysis. If you're using documents or archival records, develop a system for coding and categorizing the data.

6. Analyze the data

Analysis involves interpreting your data to draw out meaningful insights; it is in this stage that your findings start to take shape. Depending on the nature of your data and your research question, you might use any of a variety of analysis methods. For qualitative data, you might employ thematic analysis to identify key themes or grounded theory to generate a new theoretical framework. For quantitative data, you might use statistical analysis to identify patterns or correlations.

Always be open to unexpected findings. Your initial hypotheses might not be supported, or you might uncover new insights that you hadn't initially considered. Remember that all data, whether they fit neatly into your analysis or not, provide valuable insights and contribute to the holistic understanding of your case.

7. Write the case study report

After analyzing the data, it's finally time to compose your case study. In terms of structure, a typical case study might consist of an introduction, background information, the collected data (results), analysis of that data, and the conclusion. Here's a brief breakdown of each section:

• Introduction: The introduction should be brief but engaging, providing a clear statement of the research question or problem, explaining why the case was chosen, and outlining what the case study will cover.
• Background: The background provides the context for your case. Describe the case, its history, and any relevant information that will help readers understand the situation.
• Results: This section should provide a comprehensive account of what you found, without interpretation or opinion. Present your findings in a clear, organized manner. Use visuals such as charts or graphs if they aid comprehension.
• Analysis: This section should provide your interpretations and arguments. Discuss the patterns, themes, or relationships you've identified in your data. Explain what these findings mean in relation to your research question.
• Conclusion: Finally, summarize the key insights from your case study along with their implications. Discuss the limitations of your study and propose avenues for future research.

8. Review and revise

The process of writing a case study doesn't actually end when the report is written; you also need to review your writing for coherence, clarity, and correctness. Don't underestimate the importance of this step! Make sure the information flows logically and that your arguments are well-supported. Check for any grammar or spelling errors. Having a peer or mentor review your work can be incredibly helpful as they provide a fresh perspective and can catch mistakes you might have missed.

9. Get approval if required

If your case study involves human subjects, you may need to obtain approval from an ethical review board. You'll also need to obtain informed consent from your subjects and ensure you respect their privacy and confidentiality throughout the research process. Always follow your institution's ethical guidelines and any other relevant legislation .

Practical tips for writing a compelling case study

Getting through all those steps can feel like a formidable challenge, but here are some practical tips to make the process more manageable:

Be systematic and organized

Given the importance of detail in case studies, it's vital to be systematic and organized from the get-go. This means keeping meticulous records of your data, your sources, and any changes to your research design. A good practice is to maintain a research journal or log where you can record your process, thoughts, and reflections.

In addition, use technology to your advantage. Digital tools like citation managers can help you keep track of your sources and make formatting references a breeze, while spreadsheet or database software can assist in managing and organizing your data. Developing a consistent system for labeling and storing information at the outset will save you time and effort later when you need to retrieve data for analysis.

Stay focused

One common pitfall in research and writing is loss of focus: getting sidetracked by interesting but ultimately irrelevant digressions, which can be very easy, especially when you're dealing with a rich and complex case. Always remember your research question and objectives, and let these guide your study at every step. It's perfectly acceptable – and in fact advisable – to delineate what your study will not cover. Setting clear boundaries can help you stay focused and manage the scope of your study effectively.

Use visual aids

Visual aids such as charts, diagrams, or photographs can greatly enhance your case study. They provide readers with a break from the monotony of text and can communicate complex data or relationships more easily. For instance, if you're presenting a lot of numerical data, consider using a chart or graph. If you're describing a process or sequence of events, portraying it in a flowchart or timeline might be useful. Remember, the goal is to aid comprehension, so make sure your visual aids are clear, well-labeled, and integrated into the text.

Include direct quotes

If your case study involves interviews, including direct quotes can add depth and a sense of the personal to your findings. They provide readers with a firsthand perspective and make your case study more engaging.

When using quotes, be sure to integrate them smoothly into your text. Provide enough context so readers understand the quote's relevance. Also, remember to adhere to ethical guidelines– always respect confidentiality and anonymity agreements.

Maintain ethical standards

Ethics is a fundamental consideration in all research, including case studies. Ensure you have proper consent from participants, respect their privacy, and accurately present your findings without manipulation.

Misrepresenting data or failing to respect participants' rights can lead to serious ethical violations. Always follow your institution's ethical guidelines and any other relevant legislation. If in doubt, seek advice from a supervisor or your institution's ethics committee.

Acknowledge limitations

Every research study has limitations, which could relate to the research design, data collection methods, or other aspects of the study. Being transparent about the limitations of your study can enhance its credibility; moreover, not only does identifying limitations demonstrate your critical thinking and honesty, but it also helps readers accurately interpret your findings.

Finally, acknowledging the limitations of your work helps to set the stage for further research. By identifying aspects that your study couldn't address, you provide other researchers with avenues for building on your findings.

Learn from examples

Before you start writing your case study, it can be helpful to review some published case studies in your field. Different fields may have different conventions, and familiarizing yourself with case studies in your own field can help guide your writing. Look at the structure, tone, and style. Pay attention to how the authors present and analyze data, and how they link their findings back to the research question. You can also learn a lot from the strengths and weaknesses of previously published works. However, remember to develop your own unique voice and perspective – don't just mimic what others have done.

Design for triangulation

Triangulation involves using multiple data sources or methods to gain a more comprehensive and balanced understanding of your research topic. By coming at your research question from multiple directions, such as by examining different datasets or using different methods, you can increase the validity of your results and gain more nuanced insights.

For example, if you're studying the impact of a new teaching method in a school, you might observe classes, interview teachers, and also survey students. Each method will provide a slightly different perspective, and together, they allow you to develop a more complete picture of the teaching method's impact.

Practice reflexivity

Reflexivity involves reflecting on how your assumptions, values, or experiences might influence your research process and interpretations. As a researcher, it's essential to be aware of your potential biases and how they might shape your study.

Consider keeping a reflexivity journal where you can note your thoughts, feelings, and reflections throughout the research process. This practice can help you stay aware of your biases and ensure your research is as objective and balanced as possible.

Write for your audience

Always make sure that your writing is on target for your intended audience. If you're writing for an academic audience, for example, you'll likely use a more formal tone and include more detailed methodological information. If you're writing for practitioners or a general audience, you might use a more accessible language and focus more on practical implications.

Remember to define any technical terms or jargon, and provide sufficient context so your readers can understand your research. The goal is to communicate your findings effectively, regardless of who your readers are.

Seek feedback

Feedback is valuable for improving your case study. Consider sharing drafts with your peers, mentors, or supervisors and asking for their input. Fresh eyes can provide different perspectives, catch errors, or suggest ways to strengthen your arguments.

Remember, feedback is not personal; it's about improving your work. Be open to critique and willing to revise your work based on the feedback you receive.

Writing a case study is a meticulous process that requires clear purpose, careful planning, systematic data collection, and thoughtful analysis. Although it can be time-consuming, the rich, detailed insights a well-executed case study can provide make this study design an invaluable tool in research.

By following this guide and adopting its practical tips, you will be well on your way to crafting a compelling case study that contributes meaningful insights to your chosen field. Good luck with your research journey!

Header image by Kateryna Hliznitsova .

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Lessons learnt: examining the use of case study methodology for nursing research in the context of palliative care

Paula brogan.

School of Communication and Media, University of Ulster, Northern Ireland, UK

Felicity Hasson

Institute of Nursing Research, University of Ulster, Northern Ireland, UK

An empirical social research approach, facilitating in-depth exploration of complex, contemporary contextualised phenomena, case study research has been used internationally in healthcare studies across clinical settings, to explore systems and processes of care delivery. In the United Kingdom, case study methods have been championed by nurse researchers, particularly in the context of community nursing and palliative care provision, where its applicability is well established. Yet, dogged by conceptual confusion, case study remains largely underutilised as a research approach.

Drawing on examples from nursing and palliative care studies, this paper clarifies case study research, identifies key concepts and considers lessons learned about its potential for nursing research within the unique and complex palliative and end of life context.

A case study approach offers nurse researchers the opportunity for in-depth, contextualised understanding of the systems and processes which influence their role in palliative care delivery across settings. However, philosophical and conceptual understandings are needed and further training in case study methodology is required to enable researchers to articulate and conduct case study.

Introduction

An empirical social research approach, facilitating in-depth exploration of a contemporary phenomenon ( Yin, 2009 ), case study research has been used internationally in healthcare studies ( Anthony and Jack, 2009 ) to explore systems of palliative care ( Lalor et al., 2013 ), diverse contexts for palliative care delivery ( Sussman et al., 2011 ), roles of professional groups such as pharmacy ( O’Connor et al., 2011 ), the impact of services such as complementary therapy ( Maddalena et al., 2010 ) and nursing (Kaasalainen et al., 2013). In the United Kingdom, case study methods have been championed by nurse researchers ( Payne et al., 2006 ), particularly in the context of community nursing and palliative care provision ( Kennedy, 2005 ; Walshe et al., 2004 , 2008 ) and its applicability to palliative and end-of-life care research is established ( Goodman et al., 2012 ). Suited to the study of complex processes ( Walshe, 2011 ), case study methodology is embedded in professional guidance on the development of complex interventions ( Medical Research Council, 2008 ). Yet, case study is dogged by conceptual confusion (Flyvberg, 2006), and, despite sporadic use, remains underutilised as a research approach in healthcare settings ( Froggatt et al., 2003 ).

Illustrated by examples from nursing and palliative care studies, this paper aims to clarify conceptual understanding and identify key lessons for its application within these unique and complex contexts and, more broadly, for nursing research.

Origins and definitions

French sociologist Frederic Le Play (1806–1882) is associated with the origin of the case study approach ( Hamel et al., 1993 ). Using a purposive sample of working class families and fieldwork methods of observation and individual interview, he sought a contextualised and in-depth understanding of their individual experiences. Each family case study uncovered the unique experience of that family, but each additional family studied was another ‘ case of the lived experience’ of working class families in mid-18th century France. Thereby, Le Play used the lens of individual experience ( Yin, 2013 ) to build comparisons across families and enrich overall understanding of that complex society.

This early glimpse of the case study approach showed it to be a straightforward ‘field investigation’ ( Hamel et al., 1993 ); epistemologically pragmatic as it generated knowledge through data drawn from diverse sources, such as family members, and used the best available data collection methods then, to inform a holistic and contextualised understanding of how people operated within a complex social system ( Stake, 1995 ).

However, defining case study has become increasingly challenging since its expansion into North America in the 1800s ( Platt, 1992 ), and its use across a range of disciplines such as politics ( Gerring, 2004 ), social science ( George and Bennett, 2005 ), education ( Merriam, 1998 ) and healthcare ( Yin, 2013 ). Variously characterised as a case report, data collection method and methodology ( Anthony and Jack, 2009 ), the development of case histories as illustrations in health and social care and in education ( Merriam, 1998 ) has contributed to further confusion for researchers and readers of case study research ( Gomm et al., 2000 ). Critiques of case study note that it lacks a single definition, such that a plethora of discipline dependant interpretations ( Simons, 2009 ) and loose use of the term case study ( Tight, 2010 ) have contributed to confusion and undermined case study credibility. However, Simons ( 2009 , p. 63) advises researchers that case study must be seen within the complex nexus of political, methodological and epistemological convictions that constitute the field of enquiry, and variations of these may be glimpsed in Table 1 as definitions from four eminent and frequently cited case study authors illustrate philosophical and discipline-influenced differences in emphasis. Consequently, the case study definition selected, with its underpinning ontology and epistemology has important implications for the coherent outworking of the overall research design. It is therefore notable that many of the palliative care case studies contained in Table 2 fail to identify any such definition and this may have implications for interpretation of the quality of studies.

Definitions of case study by four key authors, showing the variation in meaning and interpretation.

Examples of Case Studies (CS) conducted in palliative care contexts.

Case study as a philosophy for the epistemology of knowledge generation

Although frequently linked to naturalistic inquiry ( Lincoln and Guba, 1986 ), interpretative/constructivist philosophy and qualitative methodology ( Stake, 1995 ), case study is not in fact bound to any single research paradigm ( Creswell, 2013 ). It is philosophically pragmatic, such that the case study design should reflect the ontological positions and epistemological considerations of the researchers and their topic of interest ( Luck et al., 2006 ). In practice, this means that case study research may pragmatically employ both qualitative and quantitative methods independently or together in order to respond to the research objectives ( Cooper et al., 2012 ; Simons, 1987 ; Stake, 2006 ). So whilst Table 2 shows that qualitative case studies are common in palliative care, epistemological variation is evident and reflects the study topic, purpose and context of the research. For example, Maddalena et al. (2010) used in-depth interview and discourse analysis to understand individual patient meaning-making; Brogan et al. (2017) used focus groups and thematic analysis as part of an embedded element of a multiple case study, to contrast the diverse perspectives of multi-disciplinary healthcare practitioners on end-of-life decision-making; Sussman et al. (2011) incorporated survey data into a mixed methods multiple case study which explored health system characteristics and quality of care delivery for cancer patients across four regions of Canada. Consequently, it is useful to ‘conceptualise (case study) as an approach to research rather than a methodology in its own right’ ( Rosenberg and Yates, 2007 , p. 448), so that a non-standardised approach exists and the case study design, its boundaries, numbers of cases and methods are guided by the stated underpinning ontological perspectives of the researcher and their topic of interest. The study then flexibly adopts the best methods to gain an in-depth, holistic and contextualised understanding of the phenomenon of interest – the latter objectives being at the core of any definition of case study research.

Key case study concepts and lessons for practice

When considering the utility of a case study approach, research conducted in complex palliative care contexts offers several insights into how central concepts translate to practice.

Contextualised understanding

Drawing on the definitions in Table 1 , Stake emphasised the particularity and intrinsic value of each individual case ( Stake, 1995 ), to emphasise the usefulness of multiple cases to increase insight ( Stake, 2006 ), analyse patterns ( Gerring, 2004 ; George and Bennett, 2005 ) and develop causal hypotheses ( Yin, 2013 ). Yet, whatever the purpose, all case studies are concerned with the crucial relationship between a phenomenon and the environment in which it has occurred. In practice therefore, case study researchers must be concerned with understanding the background systems, structures and processes that influence and interact with the phenomenon under study. This capacity for contextualised and holistic understanding is underpinned by use of multiple data collection methods, such as observation, interview and document review, used simultaneously or sequentially ( Stake, 2006 ; Scholz and Tietje, 2002 ), to mine multiple sources of data, such as participant experience ( Brogan et al., 2017 ; Kaasalainen et al., 2012 ), documents (Lalor et al., 2003) service evaluations ( Walshe et al., 2008 ), and diaries ( Skilbeck and Seymour, 2002 ). This is exemplified in a study by Walshe et al. (2011) , who investigated referral decisions made by community palliative care nurses in the UK, by capturing interview data on the self-reported perspectives of healthcare professionals, in combination with observed team meetings in which decisions were influenced, and review of the written referral policies, protocols and palliative healthcare strategies specific to those decisions. This comprehensive and complex data enabled comparison of decisional processes and their influencing factors both within and across three Primary Care Trusts, thus providing a contemporaneous understanding of the complex relationship between individual nurse's referral decisions and the impact of the organisational and professional systems that underpinned them. Enhancing rigor, such methodological triangulation importantly contributed to the richness of data analysis and the development of assertions which might be drawn from the findings ( Cooper et al., 2012 ; Stake, 2006 ).

Process-focused

Flexible data collection methods, linked to the research purpose, enables case study researchers to gather both historical and real-time data in a variety of ways. For example, Kennedy’s longitudinal case study ( Kennedy, 2002 ) observed snapshots of the initial and follow-up assessment conducted by 11 district nurses over the subsequent 12 months, enabling an exploration of the outcome and impact of their decision-making, demonstrating the usefulness of case study to understand complex roles and processes which are fluid and elusive ( Yin, 2013 ), or otherwise difficult to capture, particularly in the intimate interpersonal contexts where nursing happens.

Analytic frame

Palliative care studies reviewed frequently report the use of thematic analysis. However, whilst this approach is certainly useful to process data generated in qualitative case studies, the approach to analysis must be congruent with the research design and reflect the purpose of the research and methods used. Moreover, beyond decisions about use of thematic analysis or descriptive statistics etc., in case study, important decisions must be made about the analytic frame of the research. Gerring’s definition (2004) set out the analytic frame in which the cases studied might be understood, explaining that each unit of analysis (or case), sheds light on other units (or cases). Thus defined, an individual case offers intrinsically valuable information about a phenomenon ( Stake, 1995 ) and the purposeful selection of cases is central to case study design. This is because, viewed from a certain angle, each case is also a case of something else, such that the findings have broader implications ( Gerring, 2004 ; Simons, 2009 , 1987 ; Yin, 2013 ). In practice, this means that the case and what it is a case of, must be clearly identified and well defined at the outset of a study, since this has implications for the relevance of findings. This can be seen in a study by O’Connor et al., (2011) , who considered the perceived role of community pharmacists in palliative care teams in Australia. Each unique case included multi-disciplinary healthcare team members, such as pharmacists, doctors and nurses working in localities, whose perspectives were sought. Each locality group was a case of community pharmacy provision in palliative care settings in Australia, and findings had implications for the planning of community services overall. So, insight development was possible at an individual, group and organisational level, and inferences were made directly in relation to the parameters of that case study.

The addition of several carefully selected cases, as in multiple case studies, offers the opportunity to analyse data gained within and across cases ( Stake, 2006 ). Case selection may be made in order to explore similarities and contrasting perspectives ( Brogan et al., 2017 ), understand the various impacts of geographical differences ( Sussman et al., 2011 ), and different organisational influences ( Walshe et al., 2008 ). However, whilst repetition of data across cases may reinforce propositions made at the outset of a study, the purpose of increasing the number of cases in case study research is primarily about increasing insight development into the complexity of a phenomenon ( Stake, 2006 ). Since case study is the study of a boundaried phenomenon ( Yin, 2013 ), establishing the analytic frame then underpins the selection criteria for potentially useful cases. Such clarification is essential since it provides the lens through which to focus research ( Gerring, 2004 ; Scholz and Tietje, 2002 ; Stake, 2006 ) and permits key decisions to be made about data which may be included and that which is not applicable.

However, significantly, this information is rarely articulated within published case studies in palliative care. This is an important issue for the quality of case study research, since description of the process of refining case study parameters, establishing clear boundaries of the case, articulating propositions based on existing literature, identifying the sources of data (people, records, policies, etc.) and the ways in which data would be captured, establishes clarity and underpins a rigorous, systematic and comprehensive process ( Gibbert et al., 2008 ), which can usefully contribute to practice and policy development ( George and Bennett, 2005 ).

Shaped by organisational systems, intimate settings and significant life stage contexts, the interconnection between context and participant experience of palliative care is one example of a process of healthcare provision that is often complex, subtle and elusive ( Walshe et al., 2011 ). Case studies conducted in these swiftly changing contexts illustrate several characteristics of case study research, which make it an appropriate methodological option for nurse researchers, providing the opportunity for in-depth, contextualised understanding of the systems and processes which influence their role in palliative care delivery across settings ( Walshe et al., 2004 ) and many others who seek a contextualised, contemporaneous understanding of any complex role or process ( Yin, 2013 ; Simons, 2009 ). This fieldwork-based approach has the potential to achieve depth and breadth of insight through the pragmatic, but carefully planned and articulated, use of multiple methods of data collection in order to answer the research question ( Stake, 2006 ) when analysed systematically within a frame determined at the outset by the definition of the case and its boundaries ( Gerring, 2004 ). Yet, the methodological flexibility that is advantageous in complex contexts, may be misunderstood ( Hammersley, 2012 ), particularly where terminology is unclear ( Lather, 1996 ) or where description of the systematic and rigorous application of the approach is missing from the report ( Morrow, 2005 ). Taken as an example of one area of healthcare research, evidence suggests that palliative care studies that deal meaningfully with underpinning philosophical perspectives for their selected case study approach, or which articulate coherent links between the defined case, its boundaries and the analytical frame are rare. The impact of such omissions may be the perpetuation of confusion and out-dated perceptions about the personality and quality of case study research ( King et al., 1994 ), with implications for its wider adoption by nurses in healthcare research. Further training in case study methodology is required to promote philosophical and conceptual understanding, and to enable researchers to fully articulate, conduct and report case study, to underpin its credibility, relevance and future use ( Hammersley et al., 2000 ; Stake and Turnbull, 1982).

Key points for policy, practice and/or research

• Case study is well suited to nursing research in palliative care contexts, where in-depth understanding of participant experience, complex systems and processes of care within changing contexts is needed.
• Not bound to any single paradigm, nor defined by any methodology, case study’s pragmatism and flexibility makes it useful for studies in palliative care.
• Training is needed in the underpinning philosophical and conceptual basis of case study methodology, in order to articulate, conduct and report credible case study research, and take advantage of the opportunities it offers for the conduct of palliative and end-of-life care research.

Paula Brogan is a Lecturer in counselling and communication in the School of Communication and Media, and was recently appointed as Faculty Partnership Manager, University of Ulster. Dual qualified as a Registered Nurse with specialism in District Nursing and as a Counsellor/couple psychotherapist (Reg MBACPaccred), she has over 30 years’ clinical practice experience in community palliative care nursing and the provision of psychological care to patients and families dealing with palliative and chronic illness. Having worked across statutory, voluntary and private sectors, her PhD focused on multi-disciplinary decision-making at the end of life with patients and families in the community setting. Currently secretary of the Palliative Care Research Forum for Northern Ireland (PCRFNI), Paula’s ongoing research interests include communication and co-constructed decision-making in palliative and chronic illness, and the psychological support of individuals, couples, patient-family groups and multi-disciplinary staff responding to challenges of advanced progressive illness.

Felicity Hasson is a Senior Lecturer in the Institute of Nursing Research at the University of Ulster with 20 years’ experience in research. A social researcher by background, she has extensive experience and knowledge of qualitative, quantitative and mixed method research and has been involved in numerous research studies in palliative and end-of-life care. She completed her MSc in 1996 and her PhD from University of Ulster in 2012. Felicity sits on the Council of Partners for the All Ireland Institute of Hospice and the Palliative Care Palliative Care Research Network (PCRN) and is an executive board member for the UK Palliative Care Research Society. She holds an editorial board position on Futures and Foresight Science. Felicity has an established publication track recorded and successful history of grant applications. Her research interests include nurse and assistant workforce, workforce training, palliative care and chronic illness (malignant and non-malignant with patients, families and multi-disciplinary health care professionals) and public awareness of palliative care and end of life issues.

Sonja McIlfatrick is a Professor in Nursing and Palliative Care and has recently been appointed as the Head of School of Nursing at University of Ulster. She is an experienced clinical academic with experience in nursing and palliative care practice, education and research. She previously worked as the Head of Research for the All Ireland Institute of Hospice and Palliative Care (2011-2014) and led the establishment of the All Ireland Palliative Care Research Network (PCRN) and is the current Chair of the Strategic Scientific Committee for the PCRN (AIIHPC). Sonja is an Executive Board member for the UK, Palliative Care Research Society and is member of the Research Scientific Advisory Committee for Marie Curie, UK. Sonja holds an Editorial Board position on the International Journal of Palliative Nursing and Journal of Research in Nursing. Professor McIlfatrick has published widely in academic and professional journals focused on palliative care research and has a successful history of grant acquisition. Sonja has a keen interest in doctoral education and is the current President of the International Network of Doctoral Education in Nursing (INDEN). Her research interests include, palliative care in chronic illness, decision making at end of life; public awareness of palliative care and psychosocial support for family caregivers affected by advanced disease.

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Ethics statement

Ethical permission was not required for this paper.

The author(s) received no financial support for the research, authorship, and/or publication of this article.

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Organizing Your Social Sciences Research Assignments

• Annotated Bibliography
• Analyzing a Scholarly Journal Article
• Group Presentations
• Dealing with Nervousness
• Using Visual Aids
• Grading Someone Else's Paper
• Types of Structured Group Activities
• Group Project Survival Skills
• Leading a Class Discussion
• Multiple Book Review Essay
• Reviewing Collected Works
• Writing a Case Analysis Paper
• Writing a Case Study
• About Informed Consent
• Writing Field Notes
• Writing a Policy Memo
• Writing a Reflective Paper
• Writing a Research Proposal
• Generative AI and Writing
• Acknowledgments

Definition and Introduction

Case analysis is a problem-based teaching and learning method that involves critically analyzing complex scenarios within an organizational setting for the purpose of placing the student in a “real world” situation and applying reflection and critical thinking skills to contemplate appropriate solutions, decisions, or recommended courses of action. It is considered a more effective teaching technique than in-class role playing or simulation activities. The analytical process is often guided by questions provided by the instructor that ask students to contemplate relationships between the facts and critical incidents described in the case.

Cases generally include both descriptive and statistical elements and rely on students applying abductive reasoning to develop and argue for preferred or best outcomes [i.e., case scenarios rarely have a single correct or perfect answer based on the evidence provided]. Rather than emphasizing theories or concepts, case analysis assignments emphasize building a bridge of relevancy between abstract thinking and practical application and, by so doing, teaches the value of both within a specific area of professional practice.

Given this, the purpose of a case analysis paper is to present a structured and logically organized format for analyzing the case situation. It can be assigned to students individually or as a small group assignment and it may include an in-class presentation component. Case analysis is predominately taught in economics and business-related courses, but it is also a method of teaching and learning found in other applied social sciences disciplines, such as, social work, public relations, education, journalism, and public administration.

Ellet, William. The Case Study Handbook: A Student's Guide . Revised Edition. Boston, MA: Harvard Business School Publishing, 2018; Christoph Rasche and Achim Seisreiner. Guidelines for Business Case Analysis . University of Potsdam; Writing a Case Analysis . Writing Center, Baruch College; Volpe, Guglielmo. "Case Teaching in Economics: History, Practice and Evidence." Cogent Economics and Finance 3 (December 2015). doi:https://doi.org/10.1080/23322039.2015.1120977.

How to Approach Writing a Case Analysis Paper

The organization and structure of a case analysis paper can vary depending on the organizational setting, the situation, and how your professor wants you to approach the assignment. Nevertheless, preparing to write a case analysis paper involves several important steps. As Hawes notes, a case analysis assignment “...is useful in developing the ability to get to the heart of a problem, analyze it thoroughly, and to indicate the appropriate solution as well as how it should be implemented” [p.48]. This statement encapsulates how you should approach preparing to write a case analysis paper.

Before you begin to write your paper, consider the following analytical procedures:

• Review the case to get an overview of the situation . A case can be only a few pages in length, however, it is most often very lengthy and contains a significant amount of detailed background information and statistics, with multilayered descriptions of the scenario, the roles and behaviors of various stakeholder groups, and situational events. Therefore, a quick reading of the case will help you gain an overall sense of the situation and illuminate the types of issues and problems that you will need to address in your paper. If your professor has provided questions intended to help frame your analysis, use them to guide your initial reading of the case.
• Read the case thoroughly . After gaining a general overview of the case, carefully read the content again with the purpose of understanding key circumstances, events, and behaviors among stakeholder groups. Look for information or data that appears contradictory, extraneous, or misleading. At this point, you should be taking notes as you read because this will help you develop a general outline of your paper. The aim is to obtain a complete understanding of the situation so that you can begin contemplating tentative answers to any questions your professor has provided or, if they have not provided, developing answers to your own questions about the case scenario and its connection to the course readings,lectures, and class discussions.
• Determine key stakeholder groups, issues, and events and the relationships they all have to each other . As you analyze the content, pay particular attention to identifying individuals, groups, or organizations described in the case and identify evidence of any problems or issues of concern that impact the situation in a negative way. Other things to look for include identifying any assumptions being made by or about each stakeholder, potential biased explanations or actions, explicit demands or ultimatums , and the underlying concerns that motivate these behaviors among stakeholders. The goal at this stage is to develop a comprehensive understanding of the situational and behavioral dynamics of the case and the explicit and implicit consequences of each of these actions.
• Identify the core problems . The next step in most case analysis assignments is to discern what the core [i.e., most damaging, detrimental, injurious] problems are within the organizational setting and to determine their implications. The purpose at this stage of preparing to write your analysis paper is to distinguish between the symptoms of core problems and the core problems themselves and to decide which of these must be addressed immediately and which problems do not appear critical but may escalate over time. Identify evidence from the case to support your decisions by determining what information or data is essential to addressing the core problems and what information is not relevant or is misleading.
• Explore alternative solutions . As noted, case analysis scenarios rarely have only one correct answer. Therefore, it is important to keep in mind that the process of analyzing the case and diagnosing core problems, while based on evidence, is a subjective process open to various avenues of interpretation. This means that you must consider alternative solutions or courses of action by critically examining strengths and weaknesses, risk factors, and the differences between short and long-term solutions. For each possible solution or course of action, consider the consequences they may have related to their implementation and how these recommendations might lead to new problems. Also, consider thinking about your recommended solutions or courses of action in relation to issues of fairness, equity, and inclusion.
• Decide on a final set of recommendations . The last stage in preparing to write a case analysis paper is to assert an opinion or viewpoint about the recommendations needed to help resolve the core problems as you see them and to make a persuasive argument for supporting this point of view. Prepare a clear rationale for your recommendations based on examining each element of your analysis. Anticipate possible obstacles that could derail their implementation. Consider any counter-arguments that could be made concerning the validity of your recommended actions. Finally, describe a set of criteria and measurable indicators that could be applied to evaluating the effectiveness of your implementation plan.

Use these steps as the framework for writing your paper. Remember that the more detailed you are in taking notes as you critically examine each element of the case, the more information you will have to draw from when you begin to write. This will save you time.

NOTE : If the process of preparing to write a case analysis paper is assigned as a student group project, consider having each member of the group analyze a specific element of the case, including drafting answers to the corresponding questions used by your professor to frame the analysis. This will help make the analytical process more efficient and ensure that the distribution of work is equitable. This can also facilitate who is responsible for drafting each part of the final case analysis paper and, if applicable, the in-class presentation.

Framework for Case Analysis . College of Management. University of Massachusetts; Hawes, Jon M. "Teaching is Not Telling: The Case Method as a Form of Interactive Learning." Journal for Advancement of Marketing Education 5 (Winter 2004): 47-54; Rasche, Christoph and Achim Seisreiner. Guidelines for Business Case Analysis . University of Potsdam; Writing a Case Study Analysis . University of Arizona Global Campus Writing Center; Van Ness, Raymond K. A Guide to Case Analysis . School of Business. State University of New York, Albany; Writing a Case Analysis . Business School, University of New South Wales.

Structure and Writing Style

A case analysis paper should be detailed, concise, persuasive, clearly written, and professional in tone and in the use of language . As with other forms of college-level academic writing, declarative statements that convey information, provide a fact, or offer an explanation or any recommended courses of action should be based on evidence. If allowed by your professor, any external sources used to support your analysis, such as course readings, should be properly cited under a list of references. The organization and structure of case analysis papers can vary depending on your professor’s preferred format, but its structure generally follows the steps used for analyzing the case.

Introduction

The introduction should provide a succinct but thorough descriptive overview of the main facts, issues, and core problems of the case . The introduction should also include a brief summary of the most relevant details about the situation and organizational setting. This includes defining the theoretical framework or conceptual model on which any questions were used to frame your analysis.

Following the rules of most college-level research papers, the introduction should then inform the reader how the paper will be organized. This includes describing the major sections of the paper and the order in which they will be presented. Unless you are told to do so by your professor, you do not need to preview your final recommendations in the introduction. U nlike most college-level research papers , the introduction does not include a statement about the significance of your findings because a case analysis assignment does not involve contributing new knowledge about a research problem.

Background Analysis

Background analysis can vary depending on any guiding questions provided by your professor and the underlying concept or theory that the case is based upon. In general, however, this section of your paper should focus on:

• Providing an overarching analysis of problems identified from the case scenario, including identifying events that stakeholders find challenging or troublesome,
• Identifying assumptions made by each stakeholder and any apparent biases they may exhibit,
• Describing any demands or claims made by or forced upon key stakeholders, and
• Highlighting any issues of concern or complaints expressed by stakeholders in response to those demands or claims.

These aspects of the case are often in the form of behavioral responses expressed by individuals or groups within the organizational setting. However, note that problems in a case situation can also be reflected in data [or the lack thereof] and in the decision-making, operational, cultural, or institutional structure of the organization. Additionally, demands or claims can be either internal and external to the organization [e.g., a case analysis involving a president considering arms sales to Saudi Arabia could include managing internal demands from White House advisors as well as demands from members of Congress].

Throughout this section, present all relevant evidence from the case that supports your analysis. Do not simply claim there is a problem, an assumption, a demand, or a concern; tell the reader what part of the case informed how you identified these background elements.

Identification of Problems

In most case analysis assignments, there are problems, and then there are problems . Each problem can reflect a multitude of underlying symptoms that are detrimental to the interests of the organization. The purpose of identifying problems is to teach students how to differentiate between problems that vary in severity, impact, and relative importance. Given this, problems can be described in three general forms: those that must be addressed immediately, those that should be addressed but the impact is not severe, and those that do not require immediate attention and can be set aside for the time being.

All of the problems you identify from the case should be identified in this section of your paper, with a description based on evidence explaining the problem variances. If the assignment asks you to conduct research to further support your assessment of the problems, include this in your explanation. Remember to cite those sources in a list of references. Use specific evidence from the case and apply appropriate concepts, theories, and models discussed in class or in relevant course readings to highlight and explain the key problems [or problem] that you believe must be solved immediately and describe the underlying symptoms and why they are so critical.

Alternative Solutions

This section is where you provide specific, realistic, and evidence-based solutions to the problems you have identified and make recommendations about how to alleviate the underlying symptomatic conditions impacting the organizational setting. For each solution, you must explain why it was chosen and provide clear evidence to support your reasoning. This can include, for example, course readings and class discussions as well as research resources, such as, books, journal articles, research reports, or government documents. In some cases, your professor may encourage you to include personal, anecdotal experiences as evidence to support why you chose a particular solution or set of solutions. Using anecdotal evidence helps promote reflective thinking about the process of determining what qualifies as a core problem and relevant solution .

Throughout this part of the paper, keep in mind the entire array of problems that must be addressed and describe in detail the solutions that might be implemented to resolve these problems.

Recommended Courses of Action

In some case analysis assignments, your professor may ask you to combine the alternative solutions section with your recommended courses of action. However, it is important to know the difference between the two. A solution refers to the answer to a problem. A course of action refers to a procedure or deliberate sequence of activities adopted to proactively confront a situation, often in the context of accomplishing a goal. In this context, proposed courses of action are based on your analysis of alternative solutions. Your description and justification for pursuing each course of action should represent the overall plan for implementing your recommendations.

For each course of action, you need to explain the rationale for your recommendation in a way that confronts challenges, explains risks, and anticipates any counter-arguments from stakeholders. Do this by considering the strengths and weaknesses of each course of action framed in relation to how the action is expected to resolve the core problems presented, the possible ways the action may affect remaining problems, and how the recommended action will be perceived by each stakeholder.

In addition, you should describe the criteria needed to measure how well the implementation of these actions is working and explain which individuals or groups are responsible for ensuring your recommendations are successful. In addition, always consider the law of unintended consequences. Outline difficulties that may arise in implementing each course of action and describe how implementing the proposed courses of action [either individually or collectively] may lead to new problems [both large and small].

Throughout this section, you must consider the costs and benefits of recommending your courses of action in relation to uncertainties or missing information and the negative consequences of success.

The conclusion should be brief and introspective. Unlike a research paper, the conclusion in a case analysis paper does not include a summary of key findings and their significance, a statement about how the study contributed to existing knowledge, or indicate opportunities for future research.

Begin by synthesizing the core problems presented in the case and the relevance of your recommended solutions. This can include an explanation of what you have learned about the case in the context of your answers to the questions provided by your professor. The conclusion is also where you link what you learned from analyzing the case with the course readings or class discussions. This can further demonstrate your understanding of the relationships between the practical case situation and the theoretical and abstract content of assigned readings and other course content.

Problems to Avoid

The literature on case analysis assignments often includes examples of difficulties students have with applying methods of critical analysis and effectively reporting the results of their assessment of the situation. A common reason cited by scholars is that the application of this type of teaching and learning method is limited to applied fields of social and behavioral sciences and, as a result, writing a case analysis paper can be unfamiliar to most students entering college.

After you have drafted your paper, proofread the narrative flow and revise any of these common errors:

• Unnecessary detail in the background section . The background section should highlight the essential elements of the case based on your analysis. Focus on summarizing the facts and highlighting the key factors that become relevant in the other sections of the paper by eliminating any unnecessary information.
• Analysis relies too much on opinion . Your analysis is interpretive, but the narrative must be connected clearly to evidence from the case and any models and theories discussed in class or in course readings. Any positions or arguments you make should be supported by evidence.
• Analysis does not focus on the most important elements of the case . Your paper should provide a thorough overview of the case. However, the analysis should focus on providing evidence about what you identify are the key events, stakeholders, issues, and problems. Emphasize what you identify as the most critical aspects of the case to be developed throughout your analysis. Be thorough but succinct.
• Writing is too descriptive . A paper with too much descriptive information detracts from your analysis of the complexities of the case situation. Questions about what happened, where, when, and by whom should only be included as essential information leading to your examination of questions related to why, how, and for what purpose.
• Inadequate definition of a core problem and associated symptoms . A common error found in case analysis papers is recommending a solution or course of action without adequately defining or demonstrating that you understand the problem. Make sure you have clearly described the problem and its impact and scope within the organizational setting. Ensure that you have adequately described the root causes w hen describing the symptoms of the problem.
• Recommendations lack specificity . Identify any use of vague statements and indeterminate terminology, such as, “A particular experience” or “a large increase to the budget.” These statements cannot be measured and, as a result, there is no way to evaluate their successful implementation. Provide specific data and use direct language in describing recommended actions.
• Unrealistic, exaggerated, or unattainable recommendations . Review your recommendations to ensure that they are based on the situational facts of the case. Your recommended solutions and courses of action must be based on realistic assumptions and fit within the constraints of the situation. Also note that the case scenario has already happened, therefore, any speculation or arguments about what could have occurred if the circumstances were different should be revised or eliminated.

Bee, Lian Song et al. "Business Students' Perspectives on Case Method Coaching for Problem-Based Learning: Impacts on Student Engagement and Learning Performance in Higher Education." Education & Training 64 (2022): 416-432; The Case Analysis . Fred Meijer Center for Writing and Michigan Authors. Grand Valley State University; Georgallis, Panikos and Kayleigh Bruijn. "Sustainability Teaching using Case-Based Debates." Journal of International Education in Business 15 (2022): 147-163; Hawes, Jon M. "Teaching is Not Telling: The Case Method as a Form of Interactive Learning." Journal for Advancement of Marketing Education 5 (Winter 2004): 47-54; Georgallis, Panikos, and Kayleigh Bruijn. "Sustainability Teaching Using Case-based Debates." Journal of International Education in Business 15 (2022): 147-163; .Dean,  Kathy Lund and Charles J. Fornaciari. "How to Create and Use Experiential Case-Based Exercises in a Management Classroom." Journal of Management Education 26 (October 2002): 586-603; Klebba, Joanne M. and Janet G. Hamilton. "Structured Case Analysis: Developing Critical Thinking Skills in a Marketing Case Course." Journal of Marketing Education 29 (August 2007): 132-137, 139; Klein, Norman. "The Case Discussion Method Revisited: Some Questions about Student Skills." Exchange: The Organizational Behavior Teaching Journal 6 (November 1981): 30-32; Mukherjee, Arup. "Effective Use of In-Class Mini Case Analysis for Discovery Learning in an Undergraduate MIS Course." The Journal of Computer Information Systems 40 (Spring 2000): 15-23; Pessoa, Silviaet al. "Scaffolding the Case Analysis in an Organizational Behavior Course: Making Analytical Language Explicit." Journal of Management Education 46 (2022): 226-251: Ramsey, V. J. and L. D. Dodge. "Case Analysis: A Structured Approach." Exchange: The Organizational Behavior Teaching Journal 6 (November 1981): 27-29; Schweitzer, Karen. "How to Write and Format a Business Case Study." ThoughtCo. https://www.thoughtco.com/how-to-write-and-format-a-business-case-study-466324 (accessed December 5, 2022); Reddy, C. D. "Teaching Research Methodology: Everything's a Case." Electronic Journal of Business Research Methods 18 (December 2020): 178-188; Volpe, Guglielmo. "Case Teaching in Economics: History, Practice and Evidence." Cogent Economics and Finance 3 (December 2015). doi:https://doi.org/10.1080/23322039.2015.1120977.

Writing Tip

Ca se Study and Case Analysis Are Not the Same!

Confusion often exists between what it means to write a paper that uses a case study research design and writing a paper that analyzes a case; they are two different types of approaches to learning in the social and behavioral sciences. Professors as well as educational researchers contribute to this confusion because they often use the term "case study" when describing the subject of analysis for a case analysis paper. But you are not studying a case for the purpose of generating a comprehensive, multi-faceted understanding of a research problem. R ather, you are critically analyzing a specific scenario to argue logically for recommended solutions and courses of action that lead to optimal outcomes applicable to professional practice.

To avoid any confusion, here are twelve characteristics that delineate the differences between writing a paper using the case study research method and writing a case analysis paper:

• Case study is a method of in-depth research and rigorous inquiry ; case analysis is a reliable method of teaching and learning . A case study is a modality of research that investigates a phenomenon for the purpose of creating new knowledge, solving a problem, or testing a hypothesis using empirical evidence derived from the case being studied. Often, the results are used to generalize about a larger population or within a wider context. The writing adheres to the traditional standards of a scholarly research study. A case analysis is a pedagogical tool used to teach students how to reflect and think critically about a practical, real-life problem in an organizational setting.
• The researcher is responsible for identifying the case to study; a case analysis is assigned by your professor . As the researcher, you choose the case study to investigate in support of obtaining new knowledge and understanding about the research problem. The case in a case analysis assignment is almost always provided, and sometimes written, by your professor and either given to every student in class to analyze individually or to a small group of students, or students select a case to analyze from a predetermined list.
• A case study is indeterminate and boundless; a case analysis is predetermined and confined . A case study can be almost anything [see item 9 below] as long as it relates directly to examining the research problem. This relationship is the only limit to what a researcher can choose as the subject of their case study. The content of a case analysis is determined by your professor and its parameters are well-defined and limited to elucidating insights of practical value applied to practice.
• Case study is fact-based and describes actual events or situations; case analysis can be entirely fictional or adapted from an actual situation . The entire content of a case study must be grounded in reality to be a valid subject of investigation in an empirical research study. A case analysis only needs to set the stage for critically examining a situation in practice and, therefore, can be entirely fictional or adapted, all or in-part, from an actual situation.
• Research using a case study method must adhere to principles of intellectual honesty and academic integrity; a case analysis scenario can include misleading or false information . A case study paper must report research objectively and factually to ensure that any findings are understood to be logically correct and trustworthy. A case analysis scenario may include misleading or false information intended to deliberately distract from the central issues of the case. The purpose is to teach students how to sort through conflicting or useless information in order to come up with the preferred solution. Any use of misleading or false information in academic research is considered unethical.
• Case study is linked to a research problem; case analysis is linked to a practical situation or scenario . In the social sciences, the subject of an investigation is most often framed as a problem that must be researched in order to generate new knowledge leading to a solution. Case analysis narratives are grounded in real life scenarios for the purpose of examining the realities of decision-making behavior and processes within organizational settings. A case analysis assignments include a problem or set of problems to be analyzed. However, the goal is centered around the act of identifying and evaluating courses of action leading to best possible outcomes.
• The purpose of a case study is to create new knowledge through research; the purpose of a case analysis is to teach new understanding . Case studies are a choice of methodological design intended to create new knowledge about resolving a research problem. A case analysis is a mode of teaching and learning intended to create new understanding and an awareness of uncertainty applied to practice through acts of critical thinking and reflection.
• A case study seeks to identify the best possible solution to a research problem; case analysis can have an indeterminate set of solutions or outcomes . Your role in studying a case is to discover the most logical, evidence-based ways to address a research problem. A case analysis assignment rarely has a single correct answer because one of the goals is to force students to confront the real life dynamics of uncertainly, ambiguity, and missing or conflicting information within professional practice. Under these conditions, a perfect outcome or solution almost never exists.
• Case study is unbounded and relies on gathering external information; case analysis is a self-contained subject of analysis . The scope of a case study chosen as a method of research is bounded. However, the researcher is free to gather whatever information and data is necessary to investigate its relevance to understanding the research problem. For a case analysis assignment, your professor will often ask you to examine solutions or recommended courses of action based solely on facts and information from the case.
• Case study can be a person, place, object, issue, event, condition, or phenomenon; a case analysis is a carefully constructed synopsis of events, situations, and behaviors . The research problem dictates the type of case being studied and, therefore, the design can encompass almost anything tangible as long as it fulfills the objective of generating new knowledge and understanding. A case analysis is in the form of a narrative containing descriptions of facts, situations, processes, rules, and behaviors within a particular setting and under a specific set of circumstances.
• Case study can represent an open-ended subject of inquiry; a case analysis is a narrative about something that has happened in the past . A case study is not restricted by time and can encompass an event or issue with no temporal limit or end. For example, the current war in Ukraine can be used as a case study of how medical personnel help civilians during a large military conflict, even though circumstances around this event are still evolving. A case analysis can be used to elicit critical thinking about current or future situations in practice, but the case itself is a narrative about something finite and that has taken place in the past.
• Multiple case studies can be used in a research study; case analysis involves examining a single scenario . Case study research can use two or more cases to examine a problem, often for the purpose of conducting a comparative investigation intended to discover hidden relationships, document emerging trends, or determine variations among different examples. A case analysis assignment typically describes a stand-alone, self-contained situation and any comparisons among cases are conducted during in-class discussions and/or student presentations.

The Case Analysis . Fred Meijer Center for Writing and Michigan Authors. Grand Valley State University; Mills, Albert J. , Gabrielle Durepos, and Eiden Wiebe, editors. Encyclopedia of Case Study Research . Thousand Oaks, CA: SAGE Publications, 2010; Ramsey, V. J. and L. D. Dodge. "Case Analysis: A Structured Approach." Exchange: The Organizational Behavior Teaching Journal 6 (November 1981): 27-29; Yin, Robert K. Case Study Research and Applications: Design and Methods . 6th edition. Thousand Oaks, CA: Sage, 2017; Crowe, Sarah et al. “The Case Study Approach.” BMC Medical Research Methodology 11 (2011):  doi: 10.1186/1471-2288-11-100; Yin, Robert K. Case Study Research: Design and Methods . 4th edition. Thousand Oaks, CA: Sage Publishing; 1994.

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Nursing Case Studies with Answers

Explore Nursing Case Studies with Answers and examples in Carepatron's free downloadable PDF. Enhance your nursing knowledge and prepare for exams with practical scenarios.

By Wynona Jugueta on Mar 25, 2024.

Fact Checked by Ericka Pingol.

What is a case study?

A case study in medicine is a detailed report of a patient's experience with a disease, treatment, or condition. It typically includes the patient's medical history, symptoms, diagnostic tests, treatment course, and outcome.

Some key things to know about medical case studies template . First, they delve deep into the specifics of a single case, providing a rich understanding of a particular medical situation.

Medical professionals use case studies to learn about rare diseases, unusual presentations of common conditions, and the decision-making process involved in complex cases.

Case studies can identify exciting areas for further investigation through more rigorous clinical trials. While informative, they can't be used to develop general treatment guidelines because they only focus on a single case.

Overall, medical case studies are valuable tools for medical education and research, offering insights into human health and disease complexities.

Printable Nursing Case Studies with Answers

Download this Nursing Case Studies with Answers to analyze complex clinical situations, identify priority needs, and develop effective care plans tailored to individual patients.

What is in a nursing case study?

A nursing case study is a detailed examination of a patient's health condition, treatment plan, and overall care journey, specifically from the perspective of nursing practice. These case studies are essential components of nursing education and professional development, providing valuable insights into clinical scenarios and patient care experiences.

In a case nursing study template , various elements are typically included to comprehensively understand the patient's situation. First and foremost, the case study outlines the patient's demographic information, including age, gender, medical history, and presenting symptoms. This demographic overview sets the stage for understanding the context in which healthcare interventions occur.

Moreover, nursing case studies often delve into the nursing assessment process, highlighting the initial and ongoing assessments nurses conduct to gather relevant patient health status data. These assessments involve physical examinations, vital sign monitoring, and assessment tools to identify potential health issues and risk factors.

Critical thinking skills are essential in nursing case studies, as they enable nurses to analyze complex clinical situations, identify priority needs, and develop effective care plans tailored to individual patients. Nursing students and experienced nurses use case studies as opportunities to enhance their critical thinking abilities and clinical decision-making processes.

Nursing case studies serve several vital purposes within healthcare education and professional practice, whether they are a primary care physician or a group of nursing students. Let's explore each purpose in detail:

Enhancing clinical reasoning skills

One primary purpose of nursing case studies is to enhance nursing students' and practicing nurses' clinical reasoning skills. By presenting realistic patient scenarios, case studies challenge individuals to analyze clinical data, interpret findings, and develop appropriate nursing interventions. This process promotes critical thinking and problem-solving abilities essential for effective nursing practice.

Applying theoretical knowledge to practice

Nursing case studies provide a bridge between theoretical knowledge and practical application. They allow nursing students to apply concepts learned in the classroom to real-world patient care situations. By engaging with case studies, students can integrate theoretical principles with clinical practice, gaining a deeper understanding of nursing concepts and their relevance to patient care.

Facilitating interdisciplinary collaboration

Another purpose of nursing case studies is to facilitate interdisciplinary collaboration among healthcare professionals. Nurses often collaborate with physicians, specialists, therapists, and other team members in complex patient cases to deliver comprehensive care. Case studies offer opportunities for nurses to explore collaborative decision-making processes, communication strategies, and teamwork dynamics essential for providing quality patient care.

Promoting evidence-based practice

Nursing case studies are crucial in promoting evidence-based practice (EBP) within nursing and healthcare settings. Nurses can make informed decisions about patient care interventions by analyzing patient scenarios and considering current research evidence. Case studies encourage nurses to critically evaluate research findings, clinical guidelines, and best practices to ensure the delivery of safe, effective, and patient-centered care.

Fostering professional development

Engaging with nursing case studies contributes to the ongoing professional development of nurses at all stages of their careers. For nursing students, case studies provide valuable learning experiences that help prepare them for clinical practice. For experienced nurses, case studies offer opportunities to refine clinical skills, stay updated on emerging healthcare trends, and reflect on past experiences to improve future practice.

How to write a nursing case study?

Writing a nursing case study involves several essential steps to ensure accuracy, relevance, and clarity. Let's break down the process into actionable steps:

Step 1: Select a patient case

Begin by selecting a patient case that presents a relevant and compelling healthcare scenario. Consider factors such as the patient's demographic information, medical history, presenting symptoms (e.g., joint stiffness, pain), and healthcare needs (e.g., medication administration, vital signs monitoring). Choose a case that aligns with your learning objectives and offers meaningful analysis and discussion opportunities.

Step 2: Gather relevant data

Collect comprehensive data about the selected patient case, including medical records, test results, nursing assessments, and relevant healthcare documentation. Pay close attention to details such as the patient's current health status, past medical history (e.g., diabetes), treatment plans, and any ongoing concerns or challenges. Utilize assessment tools and techniques to evaluate the patient's condition thoroughly and identify areas of clinical significance.

Step 3: Assess the patient's needs

Based on the gathered data, evaluate the patient's needs, considering physical, emotional, social, and environmental factors. Assess the patient's pain levels, mobility, vital signs, and other relevant health indicators. Identify any potential complications, risks, or areas requiring immediate attention. Consider the patient's preferences, cultural background, and individualized care requirements in your assessment.

Step 4: Formulate nursing diagnoses

Formulate nursing diagnoses that accurately reflect the patient's health needs and priorities based on your assessment findings. Identify actual and potential nursing diagnoses related to the patient's condition, considering factors such as impaired mobility, ineffective pain management, medication adherence issues, and self-care deficits. Ensure your nursing diagnoses are specific, measurable, achievable, relevant, and time-bound (SMART).

Step 5: Develop a care plan

Develop a comprehensive care plan outlining the nursing interventions and strategies to address the patient's identified needs and nursing diagnoses. Prioritize interventions based on the patient's condition, preferences, and care goals. Include evidence-based nursing interventions to promote optimal health outcomes, manage symptoms, prevent complications, and enhance the patient's overall well-being. Collaborate with other healthcare professionals as needed to ensure coordinated care delivery.

Step 6: Implement and evaluate interventions

Implement the nursing interventions outlined in the care plan while closely monitoring the patient's response to treatment. Administer medications, provide patient education, perform nursing procedures, and coordinate care activities to effectively meet the patient's needs. Continuously evaluate the effectiveness of interventions, reassessing the patient's condition and adjusting the care plan as necessary. Document all interventions, observations, and outcomes accurately and comprehensively.

Step 7: Reflect and seek assistance

Reflect on the nursing case study process, considering what worked well, areas for improvement, and lessons learned. Seek assistance from nursing instructors, preceptors, or colleagues if you encounter challenges or have concerns about the patient's care. Collaborate with interdisciplinary team members to address complex patient issues and ensure holistic care delivery. Continuously strive to enhance your nursing practice through ongoing learning and professional development.

Nursing Case Studies with Answers example (sample)

Below is an example of a nursing case study sample created by the Carepatron team. This sample illustrates a structured framework for documenting patient cases, outlining nursing interventions, and providing corresponding answers to guide learners through the analysis process. Feel free to download the PDF and use it as a reference when formulating your own nursing case studies.

Download this free Nursing Case Studies with Answers PDF example here 

Why use Carepatron as your nursing software?

Carepatron stands out as a comprehensive and reliable solution for nursing professionals seeking efficient and streamlined workflows in their practice. With a range of features tailored to the needs of nurses and healthcare teams, Carepatron offers unparalleled support and functionality for managing various aspects of patient care.

Nurse scheduling software

One of the key advantages of Carepatron is its nurse scheduling software , which simplifies the process of creating and managing schedules for nursing staff. With intuitive scheduling tools and customizable options, nurses can easily coordinate shifts, manage availability, and ensure adequate staffing levels to meet patient needs effectively.

Telehealth platform

In addition, Carepatron offers a robust telehealth platform that facilitates remote patient monitoring, virtual consultations, and telemedicine services. This feature enables nurses to provide continuity of care beyond traditional healthcare settings, reaching patients in remote areas or those unable to attend in-person appointments.

Clinical documentation software

Furthermore, Carepatron's clinical documentation software streamlines the documentation process, allowing nurses to easily capture patient data, record assessments, and document interventions. The platform supports accurate and efficient documentation practices, ensuring compliance with regulatory standards and promoting continuity of care across healthcare settings.

Commonly asked questions

In clinical terms, a case study is a detailed examination of a patient's medical history, symptoms, diagnosis, treatment, and outcomes, typically used for educational or research purposes.

Case studies are essential in nursing as they provide real-life scenarios for nurses to apply theoretical knowledge, enhance critical thinking skills, and develop practical clinical reasoning and decision-making abilities.

Case studies in nursing education offer benefits such as promoting active learning, encouraging problem-solving skills, facilitating interdisciplinary collaboration, and fostering a deeper understanding of complex healthcare situations.

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• Published: 28 March 2024

Influence of magma intrusion on coal geochemical characteristics: a case study of Tiefa Daxing coal mine

• Xiang Fu 1 ,
• Xuan Liu 1 ,
• Qixuan Wu 1 ,
• Bin Xiao 1 &
• Chaojun Fan 1  

Scientific Reports volume  14 , Article number:  7396 ( 2024 ) Cite this article

Metrics details

• Biogeochemistry
• Environmental sciences
• Natural hazards

Magma intrusion has an important influence on the physical and mechanical properties of coal and rock. In the area of magma intrusion, disasters such as gas outburst are prone to occur. Revealing its invasion law will be conducive to disaster management and energy development. For this purpose, changes in industrial analysis components of coal, mineral composition, major oxides, trace elements, and rare earth elements of coal under the thermal metamorphism of magma intrusion were analyzed. It is found that the moisture and volatile matter contents of the thermally affected coals in the mining face are generally lower than that of normal coals, while moisture and volatile matter contents are reduced towards to the magma intrusion contact. For example, the moisture and volatile matter of coal sample M01 decreased by 64.6% and 38.6% respectively compared with coal sample M05. During magma intrusion, some minerals remain on the surface of the coal body, resulting in changes in the mineral composition of the coal body. The decrease in carbon atom net spacing, the increase in crystallite aggregation and ductility, and aromaticity in thermally affected coals have a positive impact on the improvement of coal metamorphism. Due to the influences of magmatic intrusion, the variation rules of major oxides in coal are different, and the closer to the magmatic intrusion zone, the easier the major oxides are to be depleted. However, magma intrusion will not lead to the loss of all major oxides in thermally affected coals, such as content of CaO is 54.8%, which is higher than that of coal not affected by magmatic hydrothermal fluid. Most of the trace elements in the thermally affected coals of the No. 9 coal seam are depleted. The contents of rare earth elements are low on the whole coalbasis, with an average of 29.48 μg/g, and the distribution pattern towards to magmatic intrusion shows a wide and gentle “V” curve with left high and right low, showing the characteristics of enrichment of light rare earth elements.

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Introduction

In 2023, Chinese raw coal production and coking raw coal production will be 4.66 billion tons and 1.319 billion tons, respectively, an increase of 2.9% and 5.2% compared with the same period in 2022. China’s metallurgical coal production is relatively stable in each year. From 2011 to 2023, the average metallurgical coal consumption is 275 million tons, and the metallurgical coal production in 2023 is 298 million tons, an increase of 2.82% over the same period in 2022 1 , 2 , 3 . Coal, as the leading energy in China, accounts for more than 60% of the primary energy consumption and will still be the Chinese dominant energy for a long time in the future 4 , 5 , 6 . Chinese coals have the characteristics of wide distribution and large resources, and magma intrusion into the coal seam is also commonly reported from Chinese coalfields 7 . The coal seam invaded by magma has its continuity damaged to a certain extent and its complexity increased, which leads to greater difficulty in mining. In turn, high ash content and poor coal quality greatly reduce its industrial value. The development of microstructure such as pores in coal seams is not conducive to gas closure and increases the risk of coal and gas outbursts 8 , 9 , 10 . The intrusion of magma can not only change the coal grade, adsorption capacity, and pore structure of coal seams but also affect the elemental compositions of coals. Therefore, it is of great practical significance to study the influence of basic magma intrusion on the elements and mineral composition of coals.

Zhang et al. 11 indicated that contact thermal metamorphism leads to the devolatilization of organic matter in coal and the deposition of pyrolytic carbon, resulting in the increase of Be and Ge content in thermally affected coals near the intrusion. Chen 12 investigated the magma intruded coal seam and discovered that the SiO 2 content of the intrusion gradually increased from the bottom to the top. Tang 13 found that in coal bodies invaded by magma, their porosity increased, their ability to absorb oxygen increased, and they were more susceptible to oxidation. Xu et al. 14 tested the geochemical composition of coals intruded by magma, and due to the mixed alteration of the magma and coal body, there was little difference in trace elements of coals near the magma intrusion range. Bi 15 found that the contact metamorphism and thermal evolution of igneous rock on the coal body reduced the volatile matter and moisture contents of the coal body but increased the content of fixed carbon and ash by comparing the industrial analysis and element analysis of normal coals and thermally affected coals. In this paper, we use elemental geochemistry analysis to investigate the impact of magmatic intrusion on the geochemical features of the No. 9 coal seam in the Daxing coal mine.

Geological setting

The Tiefa Basin is located in Diaobingshan City in the north of Liaoning Province (Fig.  1 ). It is 29.5 km long from north to south, 17.4 km wide from east to west, and covers an area of 513.5 km 2 . Daxing coal mine is located in the southwest of Tiefa Basin, which is controlled by a unilateral oblique fault 16 . The north–south strike of this oblique fault is 6.4 km long, the east–west width is 3.2 km, and the area is 20.48 km 2 . There are many internal faults and some undulating shortaxis anticlines with wavy distribution. The internal stratum of the basin is incomplete, and there is sedimentary discontinuity. The main stratum is the lower Cretaceous Fuxin Formation. This formation is divided into four sections: 1. The bottom sandy gravel section, which is deeply stored, and the lower part are mainly composed of gray, green, and dark brown sandy gravel. The gravels are mainly granite gneiss and quartzite gravels. The upper part is mainly composed of gray and dark gray sandstone, mixed with conglomerate. 2. The lower coal-bearing section is composed of gray black, gray white, gray sandstone, mudstone, coal seam, and carbon mudstone. 3. The middle sandstone and mudstone section is composed of gray, white, and gray fine sandstone mixed with coarse sandstone and mudstone. 4. The upper coal bearing section, which is composed of gray, gray white, and gray black sandstone, mudstone, pebbly sandstone, conglomerate, and coal seam with siderite. The coal bearing stratum is composed of Fuxin Formation of Early Cretaceous age and the only coal-bearing stratum in the coalfield. There are 12 minable coalbeds: the Nos. 2–1, 2–2, 2–3, 3–3, 4–2, 7–2, 8, 9, 9–2, 9–3, 10–1, and 10–2 coals (Fig.  2 ) 17 , 18 . The magmatic activity in Daxing coal mine is relatively intense, and its activity form is consistent with the regional situation, with two types: eruption and invasion. The eruption rock is mainly basalt, which appears in the ochre layer of the Cretaceous Sunjiawan Formation and is interbedded with sedimentary rock. The intrusive rocks are mainly diabase. The above two magmatic rocks are distributed in the coal measures, which have a great influence on the coal measures, especially the main coal seams. In addition, the magmatic activity of the coalfield can be divided into three periods. The first stage is the early Jurassic, dominated by volcanic eruptions; the late Cretaceous is the second stage, which is dominated by post-eruption reperfusion. The third activity period is the tertiary period, and diabase intrusion occupies the dominant position of igneous rock intrusion. There is a fair amount of complexity within the igneous rock composition of the N 2 908 mining face. Most of the intrusion horizon can be seen at the top of coal seams 4 and 7 19 . Igneous rock has a thickness of between 28.12 and 50.78 meters 15 .

Study area and sampling locations for coal samples. ( a ) Tieling map of Liaoning Province, China; ( b ) Sketch geological map of the Tiefa Basin; ( c ) Magma intrusion zone and sampling point location; ( d ) Site photos of magma intrusion and coal contact.

Stratigraphic column of Daxing coal mine.

Samples collection and experimental methods

The research samples were taken from the N 2 908 mining face of the Daxing coal mine. The N 2 908 mining face is located in the southwest of the North Second Mining Area, with a mining strike length of 977 m and an inclination width of 106 m and 125 m, respectively. The method of sampling of coal seams is in accordance with the national standard GB/T 482-2008. According to the different distance of magma intrusion into the mining face, five coal samples were selected at different positions of N 2 908 mining face, among which coal samples M01-M04 were heat-affected coal and M05 were normal coal. In addition, the coals of mining face S 5 709 and S 2 905 were also collected. Four coal samples were selected in the position that was completely unaffected by magma and the magma intrusion area, which were recorded as S 5 709 normal coal (# 1), S 5 709 metamorphic coal (# 2), S 2 905 normal coal (# 3), and S 2 905 metamorphic coal (# 4). The weight of each coal sample is 2 kg 15 , 20 . After the coal sample is mined, it is sealed in a sealed bag and transported to the laboratory. The coal sample is sieved into the particle size required for the experiment by mechanical crushing. After screening, the experimental coal samples with the required particle size are obtained. In order to eliminate the influence of external moisture on the coal spontaneous combustion experiment, the appropriate quality of coal samples were put into the vacuum drying box, the temperature of the drying box was adjusted to 40 °C, and the coal samples were dried for 24 h in the same vacuum environment. After the drying, the coal samples were put into the self-sealing bag to prevent the water vapor and oxygen in the air from contacting the coal samples, thus affecting the experimental results.

The standard proximate analysis (moisture, ash yield, volatile matter content, and fixed carbon) of coal samples was completed at Liaoning Technical University. After the coal samples were mechanized and crushed, the coal samples with a particle size of 80–200 µm were selected as the research object, and the 5E-MAG6600B automatic industrial analyzer was used for testing.

The analysis of major oxides, trace elements, and rare earth elements of coal samples was completed by Wuhan Shangpu Analytical Technology Co., Ltd. in China. The ZSX Primus II wavelength dispersive X-ray fluorescence spectrometer (XRF) produced by Rigaku was used for determining major oxide contents, including SiO 2 , TiO 2 , Al 2 O 3 , Fe 2 O 3 , MnO, MgO, CaO, K 2 O, Na 2 O, P 2 O 5 21 . The analysis procedure complies with the national standard GB/T14506.28-2010. Trace elements and rare earth elements in raw coals are analyzed by inductively coupled plasma mass spectrometry (ICP-MS). First, 0.500 mL (1 + 1) of HNO 3 and 1.00 ml of HF were used to digest 25.0 mg of rock powder (200 mesh) in a firmly closed Teflon screw-cap beaker. The dried sample was digested once again using 0.500 mL (1 + 1) of HNO 3 and 1.50 ml of HF after evaporation, and it was then dried once more (1 + 1) HNO 3 was then added to the sample at a volume of 2.00 mL. After drying the mixture once again, the process was repeated while adding HNO 3 . For trace element analysis, the solution was finally diluted with 1.00% HNO 3 to 50.0 mL. The analysis procedure conformed to the Chinese national standard GB/T14506.30-2010. The XRD testing was conducted using a German Brooke D8 ADBANCE X-ray diffractometer for phase analysis. The collected coal samples were mechanically crushed and ground, and the samples to be tested were obtained after 300 mesh sieve. The test conditions are as follows: X-ray tube, Cu target, Ka radiation sampling, test voltage and current are 40 kV and 30 mA respectively; the scanning speed is set to 0.1 s/step, and the sampling interval is 0.019450.

Results and discussions

Effect of magma intrusion on standard coal quality features.

The moisture (%), ash yield (%), volatile matter (%), and fixed carbon (%) contents of each coal sample are shown in Table 1 . By comparing and analyzing five coal samples from the N 2 908 mining face, it was determined that the closer the coal is to the range of igneous intrusion, the lower its moisture content. This could be due to the high temperature that accompanied the igneous intrusion, which caused the gasification of moisture in the coal body. However, the ash content increases with the decrease of the magma intrusion range, and it can be concluded that the decrease of the distance from the magma intrusion body will lead to the enhancement of contact thermal metamorphism. The volatile matter content diminishes with the decrease of the magma intrusion range, which indicates that the metamorphic degree of the coal body invaded by magma increases. Hence, the content of fixed carbon tends to be higher than that of normal coal in thermally affected coal, and the intrusion of magma is also obtained from this perspective, which will promote the metamorphism of coal.

Effects of magma intrusion on mineralogical composition

The mineral composition of coal seams intruded by magma depends on the chemical composition and crystallization conditions of magma, which is of great significance for understanding the influence of magma intrusion on coal geochemical characteristics. The minerals in the Daxing coal mine are mainly quartz and clay minerals and contain amounts of other minerals such as calcite and pyrite (Figs.  3 and 4 ). It also can be seen that the normal coals in S 5 709 and S 2 905 mining faces contains more quartz and only some kaolinite and calcite, while the calcite contents of thermally affected coals in S 5 709 and S 2 905 mining faces affected by magma intrusion significantly increases. Chen et al. 22 and Dai et al. 23 found that magmatic hydrothermal solution contains exogenic minerals such as calcite and pyrite, which is basically consistent with the results of this paper. It should be noted that the contents of calcite in thermally affected coals have increased significantly.

XRD spectra of normal and thermally affected coals.

Microscopic images of minerals in normal and thermally affected coals. ( a ) N 2 908 mining face normal coals; ( b ) N 2 908 mining face thermally affected coals; ( c ) S 5 709 mining face thermally affected coals; ( d ) S 2 905 mining face thermally affected coals.

As magma intrusion is accompanied by extremely high temperatures, the mineralogical compositions of coal could be changed. There are obvious differences in the diffraction peak spectra of minerals in normal coal and thermally affected coal. When magma infiltrates into the coal seam, some minerals will remain on the surface of the coal body, thus changing the composition of the coal body. The diffraction peak intensities of normal coal, quartz, and kaolinite in S 5 709 and S 2 905 mining faces in the study area are the highest, while other components are relatively low, indicating that these two minerals are the main components of normal coal, with a small amount of calcite. However, in thermally affected coal, the diffraction peak intensity of calcite has been greatly improved, especially in the thermally affected coal S 2 905 mining face (# 4), with a significant increase, while the diffraction peak intensity of quartz and kaolinite has been significantly reduced.

To investigate the influences of magma intrusion on the mineral composition of coals, we analyzed the XRD spectra based on prior researches and presented the relative mineral contents of unaffected and thermally affected coals in Table 2 . Table 2 shows that the normal coal sample (# 1) from the S 5 709 mining face contained 41.5% quartz, 55.6% kaolinite, and only 2.9% calcite. The thermally affected coal sample (# 2) from the S 5 709 mining face showed a significant decrease in quartz and kaolinite contents after exposure to magma intrusion, while the calcite contents increased significantly to 52.5%. The normal coal sample (# 3) from the S 2 905 mining face contained similar levels of quartz and kaolinite at 46.8% and 38.1%, respectively, and a calcite contents of 15.1%. Conversely, the thermally affected coal sample (# 4) demonstrated a significant increase in calcite contents to 61.4% and a significant reduction in quartz contents to 10.8%.

In order to further explore the influences of magma intrusion on coal structure, the 16–50° spectral region corresponding to 2θ was fitted, and the results were shown in Fig.  5 . It can be seen that the diagrams of the four coal samples correspond to the (002) peak and (100) peak at ~ 25° and ~ 40° respectively, and are much more obvious than the peaks in other positions, indicating they are related with coaly material or organic matter. The peak of (002) is the superposition of (002) band and γ band, which is related to the stacking of aromatic ring layers in coal. The (100) peak is attributed to the degree of condensation of the aromatic ring, that is, the size of the aromatic carbon network in the coal.

Curve fitting of the peaks of coal samples from 16° to 50°.

The structural parameter analysis of XRD for normal coals and thermally affected coals were shown in Table 3 . Compared with normal coals and thermally affected coals, it was found that the carbon source net spacing ( d 002 ) of metamorphized coal decreases, while the stacking degree ( L c ) and ductility ( L a ) of microcrystalline increases and the aromatic f a ( XRD ) also increase, indicating that the degree of metamorphism of the coal body increases due to the intrusion of magma.

Geochemical compositions

Major oxides.

We used the ZSX Primus II wavelength dispersive X-ray fluorescence spectrometer (XRF) produced by Rigaku was used for determining major oxide contents in coal samples. The results are shown in Table 4 . Sample M01, which was affected by magma intrusion, exhibited high proportions of CaO, SiO 2 , Fe 2 O 3 , and Al 2 O 3 , at 54.8%, 27.85%, 8.57%, and 5.60%, respectively. Together, these oxides account for 96.82% of the total major oxides contents. SiO 2 is the dominant major oxide in normal coals, while the content of SiO 2 in coals affected by heat were different, indicating that the intrusion of magma has little effect on the content of SiO 2 . This is mainly because the SiO 2 in coals mainly came from the contribution of quartz and kaolinite, which mainly existed in the form of Mosaic in coals, and it was difficult to move in the form of fluid during the later magma intrusion and heating process. The significant increase in CaO contents implies that magma intrusion into the coal seam results in CaO enrichment. Coal sample M02, which was less influenced by magma intrusion than coal sample M01, exhibits the highest contents of SiO 2 among its major oxides, at 57.35%. Additionally, the contents of Al 2 O 3 , Fe 2 O 3 , CaO, and K 2 O are higher, and the combined contents of these five major oxides account for 96.87% of the total contents. Coal sample M03 has a main element contents of SiO 2 , Al 2 O 3 , and Fe 2 O 3 , which together account for 91.01% of the total. This may be related to migmatic minerals mixed with coaly material. However, compared to other thermally affected coals and normal coals, the Fe 2 O 3 contents were significantly higher. This implies that magma intrusion was not the direct cause of the increase in Fe 2 O 3 contents in coal sample M03. Coal sample M04 has major oxides consisting mainly of SiO 2 , Al 2 O 3 , Fe 2 O 3 , and CaO, which together account for 95.36% of the total. Normal coal sample M05 has SiO 2 , Al 2 O 3 , Fe 2 O 3 , MgO, and K 2 O contents of 57.29%, 22.08%, 9.32%, 3.18%, and 3.18%, respectively, which together account for 95.05% of the total. As the contents of SiO 2 are higher than those of Al 2 O 3 , it implies that quartz provided excess silicon compared to the silicon contents of kaolinite.

In addition, it can be analyzed in Table 4 that the contents of major oxides in normal coals and thermally affected coals are quite normal. For coal sample M05, the contents of SiO 2 , TiO 2 , Al 2 O 3 , MgO, Na 2 O and K 2 O are higher than in coal samples M01-M04, which indicates that the intrusion of magma may lead to the loss of these major oxides in thermally affected coal samples. The contents of Fe 2 O 3 , MnO, CaO and P 2 O 5 in thermally affected coals are higher than those in normal coals, which may be the result of thermal contact metamorphism during magmatic intrusion. Fe 2 O 3 , MnO, and P 2 O 5 show the same change mode, indicating that they have the same source and occurrence state. The contents of SiO 2 , TiO 2 , Al 2 O 3 , MgO, Na 2 O, K 2 O, and P 2 O 5 in thermally affected coal sample M01, which is the most obviously intruded by magma, are lower than that in other thermally affected coals, indicating that the closer the coal is to the magmatic intrusion zone, the easier it is to lose its major oxides, while the variation pattern of the major oxides contents in coal far from the magma intrusion zone are not obvious.

Trace elements

We used inductively coupled plasma mass spectrometry (ICP-MS) to analyze trace elements in coals. Table 5 shows the average contents of trace elements in the coal of the Daxing coal mine and in the crust of Chinese coals and world coals. The enrichment coefficient is usually used to evaluate the enrichment degree of trace elements. Dai et al. 24 proposed an evaluation index method for the enrichment of trace elements in coal. By calculating the enrichment coefficient of trace elements in coal samples (CC is the ratio of trace elements in the studied samples to the world or Chinese coals average), they can be divided into the following six categories: abnormal enrichment (CC > 100), high enrichment (10 < CC < 100), enrichment (5 < CC < 10), slight enrichment (2 < CC < 5), normal (0.5 < CC < 2), and deficit (CC < 0.5) 25 , 26 , 27 , 28 .

In order to conveniently describe the enrichment degree of trace elements in coals, the contents of trace elements in thermally affected coals and normal coals, Chinese coals, and world coals in the Daxing coal mine coal samples are compared and analyzed based on the enrichment coefficient 1. The results are shown in Figs.  6 and 7 . In Fig.  6 , the turquoise indicator indicates that the element enrichment coefficient in coal is depleted (CC < 0.5), and the red indicator indicates that it is close to the world and Chinese coals averages (0.5 < CC < 2). In Fig.  6 a, by comparing the contents of trace elements in thermally affected coals and Chinese coals, it is found that, except for those elements of Cr, Co, Rb, Sr, Cs, and Ba, which are normal, other elements are depleted. By comparing the contents of trace elements in thermally affected coals and world coals in Fig.  6 b, it is determined that, except for Co, Zn, Rb, Sr, Cs, and Ba elements, which are normal, other elements are deficient, which is close to the analysis result in Fig.  6 a. Through the above analysis, it is found that magmatic intrusion makes most of the elements in the coal loss, which is mainly because during the coalification process, the contents of trace elements in the coals will be greatly affected by the intrusion of magmatic hydrothermal solution. According to general acceptance, after the intrusion of heavy metal rich hydrothermal solution into the coal seam, it moves and diffuses along the fractures to the surrounding rock, and the carried trace elements are precipitated under appropriate conditions, or absorbed by clay minerals or organic matter in the coals. Therefore, the element loss in coals could develop 29 . In Fig.  7 , purple indicates slight enrichment (2 < CC < 5), orange indicates enrichment (5 < CC < 10), and blue indicates high enrichment (10 < CC < 100). In Fig.  7 a, by comparing the contents of trace elements in normal coals and Chinese coals, it is found that Be, Co, Zr, Nb, Hf, Ta, Tl, and Pb are normal, while Cr is enriched, Rb is highly enriched, and other elements are slightly enriched. In Fig.  7 b, by comparing the contents of trace elements in normal coals and world coals, it is found that Be, Hf, and Tl are close to average values, while the elements of V, Cr, Zn, and Rb are enriched, with Cs being highly enriched, and other elements are slightly enriched. Based on the above analysis, it has been determined that most trace elements in the coals not affected by magmatic intrusion are slightly enriched, and some elements are highly enriched.

Comparison of trace elements in thermally affected coals from Daxing coal mine and Chinese coals, world coals. ( a ) Thermally affected coals/Chinese coals; ( b ) Thermally affected coals/world coals.

Comparison of trace elements in normal coals from Daxing coal mine and Chinese coals, world coals. ( a ) Normal coals/Chinese coals; ( b ) Normal coals/world coals.

In general, magmatic intrusion will have a certain impact on the occurrence of trace elements in coals and make them migrate or enrich. Most of the trace elements in the thermally affected coals intruded by magma in the Daxing coal mine are depleted. Only a few trace elements are normal, while most of the trace elements in the normal coals are slightly enriched.

Different trace elements in coals will have different effects on the environment. Wu et al. 30 have classified trace elements in coal according to the degree of their potential environmental impact. Although there are some differences in definitions, most of them include ten typical environmentally sensitive trace elements in coals, such as Be, Cr, Mn, Co, Ni, As, Tl, Cd, U, Hg, and Pb 31 .

In order to study the influences of magmatic intrusion on the contents change of potentially hazardous trace elements in coal, trace elements in six kinds of coal, as shown in Fig.  8 below, were selected for analysis. Among them, the Be element content of thermally affected coals are between 0.42 and 1.02 µg/g, with an average of 0.36 µg/g. The thermally affected coal sample M01, which is greatly affected by mag-matic intrusion, has the lowest Be element content, while the normal coal sample M05, which is farthest from the magmatic intrusion zone, has the highest Be element content. However, it can be seen from Fig.  8 a that the Be element content of five coal samples is lower than that of Chinese coals and world coals average. The content of Cr element in thermally affected coals is between 4.52 and 10.5 µg/g, with an average of 7.71 µg/g. In coal samples M01–M04, the content of Cr element is similar. Due to the affected of magmatic intrusion, the content of Cr element is lower than that of Chinese coals and world coals averages. In coal sample M05, the content of Cr element is higher than that of other coal samples and Chinese coals and world coals, indicating that magmatic intrusion leads to the reduction of Cr element content in thermally affected coals. The content of Ni in thermally affected coals ranges from 5.12 to 6.24 µg/g, with an average of 5.85 µg/g, and its distribution characteristics are similar to that of Cr. The content of Tl element in thermally affected coals ranges from 0.12 to 0.26 µg/g, with an average of 0.2 µg/g. It can be seen from Fig.  8 d that the content of Tl element in coal sample M05 is obviously higher than that in thermally affected coals and Chinese coals, which is close to that in world coals. Pb in metamorphic coal ranges from 2.14 to 4.93 µg/g, with an average of 2.99 µg/g. The content of U element in thermally affected coals ranges from 0.21 to 0.54 µg/g, with an average of 0.36 µg/g, and the distribution characteristics are similar to those of Cr and Ni elements. Among them, the contents of medium volatile and nonvolatile elements (Cr, Ni, etc.) are relatively high. Due to the affected of magma intrusion, the average contents of medium volatile volatile elements (Pb, Tl, etc.) in unaffected coal are generally less than 10 µg/g, which are generally low. The content of Tl element in coal sample M01 is only 0.12 µg/g.

Comparison of potentially hazardous trace elements with Chinese and world coals averages. ( a ) Be; ( b ) Cr; ( c ) Ni; ( d ) Tl; ( e ) Pb; ( f ) U.

In general, compared with Chinese coals and world coals affected by magmatic intrusion, the contents of potentially hazardous trace elements in thermally affected coals of the Daxing coal mine are lower than that of Chinese coals and world coals averages, and the contents of Cr, Ni, Tl, Pb, and U in normal coal are much higher than that of thermally affected coals. Among them, the contents of Be, Tl, and Pb all increase with the decrease in distance from the magmatic intrusion zone. Except for coal sample M05, the contents difference in other coal samples are relatively small, indicating that the magmatic intrusion has a tendency to dilute and reduce the contents of potentially hazardous trace elements in unaffected coal samples but the impact on different coal samples are slightly different.

Rare earth elements

According to the similarities and differences in the geochemical properties of rare earth elements (REE), they can be divided into the following three categories: light rare earth elements (LREE), including La, Ce, Pr, and Nd; medium rare earth elements (MREE), including Sm, Eu, Gd, Tb, Dy, and Y; and heavy rare earth elements (HREE), including Ho, Er, Tm, Yb, and Lu 32 , 33 , 34 , 35 .

The test results of thermally affected coals REE values ICP-MS in the Daxing coal mine are shown in Table 6 , and the corresponding geochemical parameters are shown in Table 7 . (La/Yb) N , (La/Sm) N , (Gd/Yb) N are the ratios of the standardized values of elemental chondrites. There are three types of enrichment of REE in coal, which are L type (light REE; (La/Lu) N  > 1), type M (medium REE; (La/Sm) N  < 1, (Gd/Lu) N  > 1) and H-type (heavy REE; (La/Lu) N  < 1). In coal sample M01, (La/Lu) N is 9.64, (La/Sm) N is 4.24, and (Gd/Lu) N is 1.85, which indicates L-type REE enrichment. Similarly, (La/Yb) N  > 1, (La/Sm) N  > 1, (Gd/Yb) N  > 1 in coal samples M02-M04, it is also enriched for L-type REE.

The total amount of REE in thermally affected coals of the Daxing coal mine is relatively low. It can be seen from Table 7 that ΣREE is 22.69–37.8 μg/g, with an average of 29.48 μg/g. The contents of rare earth elements are variable in the samples of different mines, different coal seams and single coal seam of Daxing coal mine, and the coal seams in this study area are greatly affected by magmatic intrusion. Compared with the unaffected coals in other coalfields, the contents of REE in the study area appears to be depleted. Among them, the contents of LREE ranges from 14.48 to 27.82 μg/g, with an average of 19.69 μg/g. The contents of MREE ranges from 7.27 to 10.99 μg/g, on average 8.63 μg/g. HREE contents are 0.94–1.37 μg/g, with an average of 1.16 μg/g. Among them, LREE/HREE is 11.01–22.8, with an average of 17.11, which is characterized by LREE enrichment and HREE deficit. It can be seen in Fig.  9 that the contents of REE in coal samples affected by magma intrusion are obviously different from that in coal samples not affected by magma intrusion.

The contents of REE in coal samples.

In thermally affected coals Eu are distributed between 0.53 and 0.74, with an average of 0.65. The negative Eu is obviously abnormal, as shown in Fig.  10 . Ce is distributed in 0.94–1.02, with an average of 0.97, less than 1, which means that Ce is negative anomaly. Generally, the negative anomaly of Ce is mainly caused by the following factors: seawater erosion, sedimentary source area and volcanic hydrothermal solution. Under alkaline conditions, because the water in the sediment is rich in oxygen, Ce 3+ is oxidized to Ce 4+ , showing a negative abnormality of Ce 36 . Since there was no seawater influence in the palaeomires of the Daxing coal mine, the negative abnormality of Ce may be due to the intrusion of magma and some material exchange in contact with natural coke that leads to the negative abnormality of Ce 37 .

The variation curve of δCe in coal samples from the Daxing coal mine.

The ratio of Y N to Ho N reflects the Y anomaly in the REE pattern. There are many causes of Y anomalies in coals, mainly geochemical processes in sediment source rocks, sedimentary environments (such as seawater injection) and hydrothermal fluids 38 , 39 , 40 , 41 . As shown in Fig.  11 , the Y N /Ho N in the thermally affected coals in the study area is between 1.24 and 1.44, with an average of 1.34, which shows a positive anomaly of Y. The peneration of hydrothermal solution is one of the factors leading to the positive Y anomaly in the coals. The study of Ge-rich coal in the Ulantuga deposit of Shengli Coal found that after experiencing magma intrusion, the Y content of high Ge-bearing coal is significantly higher than that of low Ge bearing coal in the same coal field 42 . The coal samples M01–M04 in the study area show Y-positive anomalies after being intruded by igneous rocks.

The variation curve of Y N /Ho N ratio in coal samples from the Daxing coal mine.

The standardized distribution pattern of rare earth element chondrites in the coal seams of Daxing coal mine are shown in Fig.  12 . It can be seen that the distribution pattern of REE in the coal seams of Daxing coal mine is similar, which is a “V ” curve of negative Eu anomaly. The degree of fractionation between LREE and HREE can be reflected by the slope of the distribution model curve between La-Y. It can also be seen intuitively from Fig.  12 that the fractionation degree between HREE is low, while that between LREE is high 43 , 44 , 45 . According to the distribution pattern of REE in the five coal samples collected, the sources of REE in the coal seams of Daxing coal mine are consistent in the peat forming stage, and the supply of terrigenous materials is relatively stable 46 .

Distribution pattern of REE in coal samples from the Daxing coal mine.

Conclusions

In this paper, X-ray fluorescence spectroscopy and inductively coupled plasma mass spectrometry were combined to study the changes of industrial analysis components and the geochemical characteristics of the major oxides, trace elements and REE of coals in the Daxing coal mine after magma intrusion, and the main conclusions are as follows:

Compared with the same coal seams and samples on the same mining face, it was found that the moisture and volatile matter contents of thermally affected coals were lower than that of normal coals, and the moisture and volatile matter content were lower the closer the distance from the magma intrusion.

During the magma intrusion process, some minerals remain on the surface of the coal body, resulting in changes in the mineral composition of the coal body. With the distance between the original carbon subnets decreasing, the degree of microcrystalline aggregation and ductility increased, and the aromatity increased, indicating that the intrusion of magma played a positive role in the improvement of the degree of coals metamorphism.

The thermally affected coals with different degrees of influenced from magma intrusion have different distribution laws of the major oxides. The closer to the magma intrusion zone, the easier the major oxides are to lose. However, magma intrusion does not make all major oxides disappear, and there are also a small number of enrichments, such as CaO and MnO.

The contents of thermally affected coals REE in the Daxing coal mine are low with a similar distribution pattern, showing a wide “V ” curve with high left and low right, which showed the characteristics of LREE enrichment.

Data availability

The data and materials presented in this study are available on request from the corresponding author.

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Acknowledgements

We appreciate the financial support of the Discipline Innovation Team of Liaoning Technical University (Grant No. LNTU20TD-30) and the Project of the Natural Science Foundation of Liaoning Province (Grant No. 2022-BS-328).

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X.F.: designed the research, discussed the results. X.L.: Writing-Original draft preparation, discussed the results, response to reviewers. Q.W.: performed numerical simulations and analyzed the results. B.X.: supervised the findings of this work. C.F.: designed the research, discussed the results.

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Fu, X., Liu, X., Wu, Q. et al. Influence of magma intrusion on coal geochemical characteristics: a case study of Tiefa Daxing coal mine. Sci Rep 14 , 7396 (2024). https://doi.org/10.1038/s41598-024-58186-5

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Towards a reference material for microplastics’ number concentration—case study of PET in water using Raman microspectroscopy

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• Oliver Jacob   ORCID: orcid.org/0000-0002-4974-5076 1   na1 ,
• Elżbieta Anna Stefaniak 2   na1 ,
• John Seghers 2 ,
• Rita La Spina 2 ,
• Gabriella F. Schirinzi 3 ,
• Konstantinos Chatzipanagis 2 ,
• Andrea Held 2 ,
• Håkan Emteborg 2 ,
• Robert Koeber 2 ,
• Martin Elsner   ORCID: orcid.org/0000-0003-4746-9052 1 &
• Natalia P. Ivleva   ORCID: orcid.org/0000-0002-7685-5166 1  

Increasing demand for size-resolved identification and quantification of microplastic particles in drinking water and environmental samples requires the adequate validation of methods and techniques that can be used for this purpose. In turn, the feasibility of such validation depends on the existence of suitable certified reference materials (CRM). A new candidate reference material (RM), consisting of polyethylene terephthalate (PET) particles and a water matrix, has been developed. Here, we examine its suitability with respect to a homogeneous and stable microplastic particle number concentration across its individual units. A measurement series employing tailor-made software for automated counting and analysis of particles ( TUM-ParticleTyper 2 ) coupled with Raman microspectroscopy showed evidence of the candidate RM homogeneity with a relative standard deviation of 12% of PET particle counts involving particle sizes >30 µm. Both the total particle count and the respective sums within distinct size classes were comparable in all selected candidate RM units. We demonstrate the feasibility of production of a reference material that is sufficiently homogeneous and stable with respect to the particle number concentration.

Graphical Abstract

Avoid common mistakes on your manuscript.

Introduction

Microplastics (MPs) have become one of the biggest analytical challenges in the last 20 years, not only due to a lack of a precise definition but also because of their constant alterations under environmental influence. The problem of defining what microplastics really are still involves many unanswered questions, despite around 20 years of scientific effort [ 1 , 2 ].

The first attempt to address the problem of small plastic particles polluting the marine environment was DIRECTIVE 2008/56/EC (Marine Strategy Framework Directive, MSFD) [ 3 ], which laid the ground for comprehensive, large-scale actions in emerging areas, such as ‘properties and quantities of marine litter’ (Annex 1, Descriptor 10). The criteria “for good environmental status relevant to the descriptors of Annex I to DIRECTIVE 2008/56/EC” are outlined in the following Commission Decision of 1.09.2010 (2010/477/EU) [ 4 ]. Descriptor 10 (Annex Part B of the Decision ) related to marine litter indicates the presence of microparticles and a need to characterise “trends in the amount, distribution and, where possible, composition of microparticles (in particular microplastics)”. This was tackled by the MSFD Technical Subgroup on Marine Litter (EC JRC); their Guidance on Monitoring of Marine Litter in European Seas [ 5 ], released in 2013, contains protocols and instructions on how to assess data on marine litter, including microlitter or ‘microplastics’, respectively. It was also emphasised that “an important part of establishing standard methods and protocols within MSFD will first be to define the appropriate size range”.

A comprehensive definition of MPs has been discussed since then, and it is still to be resolved. Although it is widely accepted that the upper limit should be set at 5 mm, the lower size limit applied in practice differs between various case studies (usually determined by a net or sieve mesh, filter pore size or the capacity of a technique in general). This lack of definition has been reflected—regarding the upper limit—in the Commission Decision (EU) 2017/848 of 17 May 2017 , “laying down criteria and methodological standards on good environmental status of marine waters (…)”, where the microlitter is described as particles < 5 mm, classified in the categories ‘artificial polymer materials’ and ‘other’ [ 6 ].

Different stakeholders (standardisation bodies, policymakers, scientists, etc.) define microplastics according to their goals. ISO/TC 63/SC 14 (Plastics/Environmental aspects) released a Technical Report ISO/TR 21960:2020 Plastics — Environmental aspects — State of knowledge and methodologies [ 7 ]. They defined microplastics as “any solid plastic particle insoluble in water with any dimension between 1 and 1000 µm (= 1 mm)”, with two additional definitions of ‘large microplastic’ (1−5 mm) and ‘macroplastic’ (above 5 mm). Another definition has been created for the restriction on intentionally added microplastics, remitted by the European Chemicals Agency (ECHA) [ 8 ]. They were defined as “material consisting of solid polymer-containing particles, to which additives or other substances may have been added, and where ≥ 1% w/w of particles have (i) all dimensions 1 µm ≤  x  ≤ 5 mm, or (ii), for fibres, a length of 3 µm ≤  x  ≤ 15 mm and length to diameter ratio of > 3.” So far, there is no agreement among stakeholders about the final definition of microplastics.

Microplastics raised considerable public concern regarding their suspected effects on human health (together with potentially released endocrine-disrupting compounds and pharmaceuticals) through drinking water. They will, therefore, be put on a so-called ‘watch list’ according to the recast DRINKING WATER DIRECTIVE (DWD) [ 9 ], which entered into force in 2021, “addressing substances or compounds of concern to the public or the scientific community on health ground” (Article 13, paragraph 8). Now, there is ongoing work within the EC to define a methodology which would be the most suitable to determine the content of microplastics in tap water.

Along with a need for methodologies, there is a need for (matrix) reference materials (RMs, as defined in ISO 17034 [ 10 ] and ISO Guide 30:2015 [ 11 ]) with microplastics. RMs, inevitable for quality assurance and quality control in good laboratory practice, are used to verify the reliability of measurement systems. According to the definition, RM must be “sufficiently homogeneous and stable with respect to one or more specified properties, which has been established to be fit for its intended use in a measurement process” [ 11 ]. Certified reference materials (CRM) are complemented by a document stating the certified values associated with uncertainty and traceability.

It is quite challenging to validate analytical methods in some emerging areas, where CRM would provide the easiest and the fastest solution. In microplastic analysis, many attempts have already been made to produce reference materials, though not by accredited RM producers [ 12 , 13 ]. In most cases, RMs for microplastics are homemade, as the one presented by von der Esch et al. (2020) [ 14 ]; thus, they are closer to quality control materials (QCM, ISO Guide 80 [ 15 ]). However, it must be emphasised that the term ‘reference material’ or ‘quality control material’ is sometimes used in publications to describe a material which properties are not assessed according to ISO 17034 and ISO Guide 80. All these issues highlight the effort around standardising analytical methods for MPs. The general need to determine microplastics, both qualitatively and quantitatively, has resulted in numerous publications with many different approaches to tackling validation in the analysis of MPs [ 16 , 17 , 18 , 19 , 20 , 21 , 22 ].

The challenges associated with producing microplastic RM are not only due to the lack of a clear definition and standardised analytical methods, but also to an ambiguous view on the impact on human health and the environment. It is rather challenging to choose a measurand if it is unclear which property of MPs should be monitored (polymer type, number concentration, mass concentration, particle size and shape, size distribution etc.). Therefore, the only reasonable solution is to apply an iterative approach, like developing simple RMs (i.e. pure standards) or simple matrix RMs (i.e. one analyte mixed with a simple matrix), which could serve in an inter-comparison or for internal quality control. These materials can then be used for the development of standard operating procedures (SOPs) and for the quality control/quality assurance of methods currently applied. With the more advanced and reliable measurements, the RM producers could prepare more complex RMs requiring more analytical skills. The last step would be a development of CRMs with assigned certified values. This whole complexity is sometimes called a ‘chicken or the egg’ problem since reference materials and standardised analytical methods cannot exist without each other. This problem has been thoroughly discussed by Emteborg et al. [ 23 ]. The RM producers need laboratories that can prove their ability to perform their analytical work according to ISO 17025 [ 24 ] and provide reliable results. The first approaches to test potential reference materials with MPs via interlaboratory study have already been reported in the literature [ 12 , 13 ]. The results reported by JRC-BAM (Bundesanstalt für Materialforschung und -prüfung) [ 25 ] and QUASIMEME-Wepal [ 26 ], as well as the EUROqCHARM project ( www.EUROqCHARM.eu ), uncovered a strong necessity for standardised documentation of applied analytical and sample preparation methods as well as RM development.

This paper shows a case study of microplastic particles in a simple matrix (such as water) which would pave the way to produce a reference material with MPs’ number concentration as the measurand. The concept of this RM type has been described elsewhere [ 27 ]. A similar material, previously used for JRC-BAM comparison, was also investigated with respect to a potential characterisation (and certification, if applicable) of the PET mass concentration through 1 H-NMR spectroscopy and gravimetry [ 28 ]. However, the determination of the particle number concentration is far more complex, even if only a simple matrix is considered. This has been revealed in the reports on the JRC-BAM interlaboratory study [ 25 ]. Here, we present a candidate RM of the kind as described in [ 25 , 27 , 28 ], which, however, has a lower PET particle number concentration. To assess the homogeneity and stability of a potential reference material with microplastics, an automated Raman microspectroscopy-based method has been used for the first time. This method enables the automated detection, quantification and morphological characterisation of (plastic) fragments in optical microscopy images, followed by automated Raman-based identification of MPs and non-plastic fragments, utilising the recently developed open-source program TUM-ParticleTyper 2 [ 29 ]. The goal of this publication is to outline the skills required for a laboratory participating in the assessment of this specific RM, where not only particle counting but also size determination and chemical identity recognition in one individual measurement are needed. We aimed to illustrate that defining a measurand of RM with microplastics is not trivial, especially when size-resolved microplastic particle number concentration has to be analysed. As the size measurement must be performed according to a specific definition of the particle size, we also systematically addressed this topic. Based on the presented case study, we have demonstrated the obstacles and opportunities that appeared during the production and analysis of a potential (candidate) RM with MPs.

Materials and methods

The candidate RM described below is based on the test material used for the JRC-BAM ILC on PET in water [ 25 , 27 , 28 ]. Each unit consists of pristine PET particles embedded in a sodium chloride layer, a surfactant solution and a bottle of demineralized water (Type 2), filtered through a 0.2 µm particle filter (Millipack, MERCK). The final material (water with PET particles) is ready to use after transferring the PET particles from the salt carrier into the water with the help of a surfactant solution. The role of surfactant is to decrease the interfacial tension between the hydrophobic particles and water. The three components are packed separately, and the reconstitution protocol is provided to help with the preparation of the final material. The idea of providing the three components separately was implemented to avoid the immediate separation of PET particles from water, which would compromise the homogeneity of the material.

Production of the candidate RM units (material quality control and processing) was done by JRC-Geel. The team from the Technical University of Munich, TUM (Institute of Water Chemistry, Chair of Analytical Chemistry and Water Chemistry, School of Natural Sciences, Technical University of Munich) performed the analytical part.

PET particles

PET (polyethylene terephthalate) material, in the form of a powder (colourless, maximum particle size 300 µm), was purchased in the market (GOODFELLOW, Cambridge, UK). Its chemical identity was verified in bulk and on the level of individual particles. Bulk PET powder was characterised by FT-Raman spectroscopy using a Bruker Vertex 70 spectrometer (Bruker, Belgium) equipped with a RAMII module for performing the measurements. The spectrum was taken using an integrated air-cooled diode-pumped Nd:YAG excitation laser operating at 1064 nm with a liquid N 2 -cooled ultrahigh sensitivity Ge detector. Spectral collection was performed across a scanning range of 250–3500 cm −1 with 4 cm −1 resolution and a laser power of 450 mW; 64 scans were averaged with the OPUS software (OPUS, v.7.5.18) being used for data acquisition. The instrument quality check using a performance qualification (PQ) test was conducted prior to the measurement. The recorded spectrum presented in the Supplementary Material (SM, Figure S1 ) is in agreement with previous Raman reports on PET [ 30 ].

The purity of the PET particles was also checked at the particle level by dispersion in ethanol and drop-by-drop transfer onto a Si wafer. The individual particles were analysed with a confocal Raman microscope inVia (Renishaw, UK). The sample was placed on a motorised stage, and a preliminary identification test was performed to set the laser parameters and optimise the Raman signal. Secondly, a high-quality image of a large analysis area was acquired. This image was then processed with the particle analysis software. This step enables the instrument to register the position of the objects under investigation by using the contrast between the particles and the background. The objects were classified according to size and then automatically analysed with Raman to obtain the polymer spectrum. Data were collected using a 10× objective, 785 nm laser, 5% laser power (approx. 10 mW at the sample), 3 accumulations of 10 s. PET reference spectra were taken from the Renishaw spectral database and collected from the Polymer Kit 1.0 PET sample [ 31 ]. The Raman spectra of individual PET particles and their mappings can be found in the SM (Figure S.2 ).

The stock suspension was prepared by mixing the PET powder and 0.05% Triton X 100 (p.a. grade, Merck) solution, stirred for 30 min and filtered through a 50 µm sonicated sieve (stainless steel, VWR, Belgium) to remove small particles. The particles collected on the sieve were transferred to a clean beaker and rinsed with ethanol. Dried PET particles were suspended in a mixture of 10% NaCl (p.a. grade, Merck) solution and 0.05% Triton X-100 solution, both filtered previously through a 0.22 µm pore size filter (Millipack, Merck). The particle number concentration and the size distribution were measured by a particle counter (PAMAS SVSS, Partikelmess- und Analysesysteme GmbH, Germany). The system was calibrated and maintained by the producer in the size range of 1–400 µm.

The aim was to achieve the number concentration of approximately 400 particles larger than 50 µm (sieve mesh) diameter. The production took place in a clean cell; all glassware and tools were cleaned in a dishwasher and rinsed with deionized water (Type 2, filtered through a 0.2 µm filter). The suspension with PET particles was stirred with an overhead stirrer, which kept the suspension in motion but without foaming. The vials, filled with PET suspension, were placed in a freeze-dryer at −40 °C. After drying, the vials contained a solid NaCl matrix with embedded PET particles and traces of Triton X-100. Transparent glass water bottles measuring 1 L were filled with deionized water (Type 2, filtered as mentioned above). The rinsing solution (0.1% v/v Triton X-100 in water) was also cleaned from particulates by filtering and then dispensed into 100 mL amber vials. The bottles with water were closed with polypropylene caps separated from the bottleneck by a metal disc. For more details on the production process, the reader is referred to Seghers et al. (2021) [ 27 ].

Reconstitution

Before analysis, the water sample has to be reconstituted by transferring the particles from the NaCl carrier (a) into water (950 mL) (b) using the provided surfactant (c). Every candidate RM unit consists of these three components (a), (b) and (c). The reconstitution protocol is attached to each unit and must be followed every time the candidate RM is to be used. The vial with the particles embedded in NaCl (a) is filled with 5 mL of the surfactant (c), shaken gently, and the content is poured into the water (b). This step is repeated eight times; one additional 5 mL portion has to be used to rinse the vial cap. In total, 50 mL of the surfactant solution (c) must be used to obtain 1 L of the water sample with PET particles. Plastic parts and tools must be avoided as much as possible (replaced by glass or metal) and the reconstituted sample has to be analysed immediately.

After reconstitution, the water samples were filtered under vacuum (∆ p  = 250 mbar) on Au-coated track-etched polycarbonate filters (pore size 0.8 µm, Analytische Produktions-, Steuerungs- und Controllgeräte GmbH, Germany), using a Sartorius filtration apparatus 16306 (25 mm glass vacuum filter holder, glass frit filter support, Sartorius, Germany). All steps were carried out in a laminar flow box (ENVAIR eco, ISO 3 standard, ENVAIR GmbH, Germany). After filtration, the filtration apparatus and the 1 L water bottle were rinsed with MilliQ water (3× 50 mL), which had been additionally filtered over a cellulose acetate filter (pore size 0.45 µm). An additional 50 mL portion was used to rinse the filtration apparatus only. Ten laboratory blank samples were collected during the sample processing, in each case immediately before filtration of the sample. Here, 200 mL of water (corresponding to the 4 × 50 mL rinsing portions described above) was used only (MilliQ, additional filtration over cellulose acetate filter, pore size 0.45 µm, from the same source as the one used for rinsing the samples and the filtration system). After collecting the blank sample, the filtration apparatus remained unchanged.

Raman measurements

Chemical identification was performed by Raman microspectroscopy (WITec apyron, WITec GmbH, Germany) using a 532 nm laser with 4.5 mW power. The settings of Raman signal collection were as follows: maximum spectral acquisition time 40 × 0.5 s, minimum required signal-to-noise ratio (SNR) of 5, spectral autofocus ranged from −10 to +360 µm. For the measurement series “ Evaluation of small particles’ content ”, an objective with 100× magnification, NA = 0.9 (working distance, WD = 1.0 mm), was used (together with the alternative spectral autofocus range from −10 to +15 µm). For all other measurement series, an objective with 20× magnification and NA = 0.4 (WD = 2.2 mm) was used. The spectral range used for observation was 150–4000 cm −1 , and for comparison with the reference spectrum (database matching), it was 590–1770 cm −1 and 2800–3200 cm −1 (Raman shift). The Raman system was calibrated with external (Si wafer) and internal (diode lamp) standards. The Raman signal intensity was checked regularly with the Si band at 520 cm −1 .

PET particles were analysed and counted by static image analysis followed by automated Raman measurements using the homemade open-source software TUM-ParticleTyper 2 [ 29 ]. The particles down to 10 µm were studied on the entire filter using “random sampling”. The mode “random window subsampling” was used to measure particles in the size range 1–50 µm. In this mode, objects are detected and chemically identified within randomly distributed small areas only (observed filter area proportion 0.5 to 1%). After image preprocessing, the functions cv.adaptiveThreshold(), cv.findContours() and cv.minAreaRect(), all from the Python project OpenCV, were used to outline the particle perimeter and particle area. From the latter, the smaller dimension of the minimum bounding rectangle (MBR) was considered as an approximation of the minimum Feret diameter.

Results and discussion

The number concentration of PET particles in a certain size range is the measurand, which value had to be determined. According to VIM 200:2012, measurand is ‘a quantity intended to be measured’ [ 32 ]. Further in [ 32 ], it is noted that ‘the specification of a measurand requires knowledge of the kind of quantity, description of the state of the phenomenon, body, or substance carrying the quantity, including any relevant component, and the chemical entities involved’.

In the case of our candidate RM, it was necessary to define a way to express a particle size class. For spherical particles, the definition of a particle size would be straightforward. However, particle sizing will always be an operationally defined measurand, as the size definition depends on the physical principle applied for its measurement [ 33 ]. When irregularly shaped objects are to be considered, various approaches are available for indicating the size. Measuring a particle size through microscopy will apply a projection diameter (two-dimensional image of a particle), which implicates a limited choice for size definition: Feret diameter, the dimensions of the minimum bounding rectangle (MBR), the equivalent projected area diameter (circular-equivalent diameter, CED), or the Martin diameter. The first three have found a wide application in microscopic research.

The difficulty of defining the measurand for irregular particles stems not only from a problem of selecting a size definition, but also from a practical approach to its measurement. Although many microscopes combined with vibrational spectroscopy are equipped with software for automatic size measurement and counting particles, there is often no option to obtain the Feret diameter or the CED. The software sometimes labels the particle dimension as ‘width’ or ‘length’. This can probably be associated with the dimensions of an object’s minimum bounding rectangle (MBR). Besides easily available freeware (i.e. ImageJ), which can be used for this purpose, many research groups also create and apply their own software to process a digital projection of a particle and to extract its parameters [ 34 ]. The commercial software WITec ParticleScout returns, among others, values for maximum and minimum Feret diameter, the dimensions of the MBR and CED. Based on the particle projections of approx. 800 PET particles from the source described above [ 25 ], Table 1 shows the relative difference between these size measures and the minimum Feret diameter ( F min ), considered the most appropriate in the following. If the size distribution based on F min is changed to an alternative basis for particle sizing, it will be shifted according to the percentage values given.

Simple geometric objects (square, “□”, and triangle, “∆”) can show significant differences between these measurements, as is the case for the longer side of the MBR and the maximum Feret diameter. However, within “real” samples, this difference gets significantly smaller. Additionally, the smaller dimension of the MBR is generally suitable as an approximation for F min , whereas the CED gives a considerably higher deviation in this respect.

Figure 1 shows a number-based particle size distribution of the stock suspension, determined by a particle counter. This technique is based on the light obscuration phenomenon, and the particles are sized according to their hydrodynamic diameter. Within the size range of interest (30 to 1000 µm), the mode is located at the size class 50–75 µm. Within smaller size ranges (1–10 µm), the expected increase in particle counts can be observed. However, particles within this size range contribute only marginally to the overall particle mass and can be excluded from the analysis using particle counting methods.

Particle size distribution in the PET stock suspension, as measured by a particle counter

Application of microscopic techniques to determine the number of particles means that the basic method applied here is counting, expressed as a ‘number of entities’. The result will always be based on the identity of these entities (size range, shape, aspect ratio, chemical identity etc.) and will be affected by the uncertainty of the methods for implementation of these underlying input quantities. In the case of plastic microparticles, this must involve not only sizing and counting but also recognition of a polymer type. Therefore, techniques combining microscopy with a chemical detection identity system seem the best choice. So far, Raman and Fourier transform (FT) infrared (IR) microspectrocopy are often used for that purpose [ 35 , 36 ]. However, with respect to (C)RM development, these analytical methods have to be first standardized and validated.

Another issue affecting the size measurement is the lateral resolution, which mainly depends on the magnification and numerical aperture (NA) of the applied objective and additional limiting factors like (possibly lower) pixel resolution achievable through software. The lower the particle size, the higher the (physical) lateral resolution should be. To measure particle sizes down to 1 µm, high magnification was needed (objective 100×, NA 0.9), which leads to the resolution of 8.86 pixels/µm, or a pixel size equal to 0.112 µm, thus passing the minimum requirements set by TUM-ParticleTyper 2 for the area of an object (>13 pixels). On the other side, an acceptable precision and a limit of quantification at the lower double-digit range of particle counts would require very time-consuming and tedious measurements. For the analysis of particles ≥10 µm, an objective with 20× magnification was used, which leads to a resolution of 0.81915 px/µm (1 pixel = 1.2207 µm), indicating a particle sizing precision of approximately 1 µm. The achievable precision of the size determination affects the precision of the counting result differently depending on the particle density at the lower limit of the size range to be considered.

This leads us directly to the question of the appropriate size range itself. The idea was to produce a material with larger PET particles, i.e. from 50 µm upwards. As already shown above (Fig. 1 ), it was possible to diminish the number of smaller PET particles in the suspension used for production, but it was not possible to eliminate all small particles. The smaller the size, the more particles can be found in the suspension and, therefore, in the final material. Based on the results for particle size distribution shown above, it was decided to measure the number of all PET particles larger than 30 µm. By variation of this cut-off diameter, we could then easily determine the effect on the PET particle number concentration to be determined, since the particle size, expressed as minimum Feret diameter F min , is known at the level of individual particles.

To become a reference material, the candidate RM had to be assessed according to the requirements of ISO 17034. Both homogeneity and stability (storage and transport) were evaluated by analysis of PET particle number concentration in the allocated units.

Determination of PET particle number concentration and particle size distribution for homogeneity assessment

Homogeneity assessment aims to prove that all the units in the whole batch of a reference material contain equal amounts of the analyte within the range of uncertainty. The number of units to be analysed is based on the total number of units in the batch, and (as a guideline) it is usually the cubic root of the total number of units in the batch. According to ISO Guide 35:2017, “a subset of units, typically 10 to 30, is chosen from the batch using a suitable sampling scheme” [ 37 ]. These units must be selected in a randomized way, covering the whole batch of produced units.

Raman microspectroscopy, in combination with the open-source software TUM-ParticleTyper 2 [ 29 ], was used for the analysis of ten units allocated to homogeneity assessment. This method of chemical identification and particle counting has been described elsewhere [ 14 , 29 , 34 , 35 ]. Additionally, the repeatability of the counting has been tested using one reconstituted and filtered water sample of this material. Six replicates of particle counting (including the size measurement and chemical identification) on the same filter indicated a relative standard deviation of PET particle numbers of 0.63%. However, this very high repeatability does not comprise the sample preparation (filtering), which in the case of microplastics, is extremely challenging and contributes largely to the method uncertainty.

The mean value of PET particle numbers in the units assigned to homogeneity assessment is 411, with an SD equal to 50 and an RSD of 12.1% ( n  = 9, as one from 10 analysed units was rejected due to justified technical reasons). The individual results are shown in the SM, Table S.1. As mentioned above, comparing the particle counts when changing the lower size limit by 1 µm helps estimate the possible shift of the final result, which is caused solely by the chosen image resolution (between 0 and 2 particles per sample). In principle, a systematic error in particle size measurement must also be assumed, although its determination is intricate. A realistic impact may be represented by the particle counts within the size class 30–40 µm or 20–30 µm, respectively. This will be discussed further in “ Evaluation of small particles’ content ”.

The results of blank measurements at the same size range are in Table S.2 (SM). No contamination from PET was detected in any case; hence, the appropriate preconditions for the analysis of PET particles are met. Other polymers were present only in negligible amounts. The principle of one blank per analysed sample was maintained for all measurement series presented in this study.

The size distribution of PET particles in analysed units determined by Raman-based method (Fig. 2 ) is similar to the size distribution in the PET stock suspension (Fig. 1 ) but shows the maximum in the size range 75–100 µm (instead of 50–75 µm). Furthermore, the number of particles in the selected size bins varies largely; narrowing down the size range, e.g. from 50 µm upwards, would not decrease the RSD of the PET particle number. On the contrary, it reaches 13.2% ( n  = 8, as particle size distribution was not available for all units). For particles above 75 µm, it is 13.4% and above 100 µm, it appeared to be 12.7%.

PET particle size distribution in the candidate RM units assigned to the homogeneity study (only eight units were used in this graph; each colour represents one unit)

Analysis of units allocated to stability assessment

A stability study can answer the question of whether the material remains stable during storage and transport. This could either be reached through isochronous studies (the units assigned to the study are kept at both reference and test temperatures for a certain period and then analysed altogether under repeatability conditions) or through a stability assessment of a similar material, which, however, has rather limited validity. Another way could be using literature data and common knowledge.

Transport stability is assessed for (C)RMs, which might decompose due to extreme conditions caused by transport. Ten units were allocated for this study: five were subjected to transportation in the trunk of a car for 4 weeks, whereas the other five were kept at 4 °C in a fridge during this period. During transport, the highest temperature recorded by a data logger (placed together with the transported vials) did not exceed 35 °C. Additionally, the vials subjected to transport conditions went through a vertical impact test by dropping (1.5 m height). Afterwards, all units were analysed the same way as the ones assigned to the homogeneity assessment. The number-based size distribution of PET particles is presented in Fig. 3 ; more detailed results are shown in Table S.3 (SM). The results of blank analyses are presented in Table S.4 (SM). Again, no contamination from PET was detected in any case, and other polymers were present only in negligible amounts.

PET particle size distribution of the candidate RM units kept at reference temperature (blue) and exposed to transport conditions (orange).

The average PET particle number in the units exposed to transport conditions ( n  = 5) and stored at reference temperature ( n  = 5) was in both cases, 405. However, the values for the transported units are more scattered, so the RSD values for both groups, i.e. units exposed to transport and kept at 4 °C, are 17.3% and 6.1%, respectively. The size classes of PET particles are equally populated, as the particle size distribution does not show any significant deviation from the one in the stock suspension (see Fig. 1 for comparison).

Storage stability was assessed via an isochronous study, with the same number of units stored at room temperature (RT) for different time intervals (therefrom zero to 6 months). Simultaneously, other units were kept at reference temperature (4 °C). The averages of the PET particle number concentration during the varying times of storage at RT remained stable; no significant changes in the particle numbers could be observed (Fig. 4 ). The dashed line (regression line) represents the trend (drift) of the values of PET particles’ number concentration. The slope was tested towards a statistically significant trend at a 95% confidence level and it appeared non-significant. Thus, the material can be stored at RT and transported without cooling elements. The detailed results are presented in Table S.5 (SM); the accompanying blanks show no signs of contamination (Table S.6, SM).

The size distribution of PET particles (Fig. 5 ) of the units assigned to storage stability assessment is consistent with the other units used for homogeneity and transport stability.

Average PET particle number concentration of the candidate RM units assigned to storage stability assessment

PET particle size distribution in the units assigned to storage stability assessment. Different colours are related to different time intervals of room temperature storage

Evaluation of small particles’ content

All particle counts reported above were linked to the size range set from 30 to 1000 µm defined at the beginning. The goal here was to evaluate the content of particles below the cut-off limit (30 µm). Six randomly selected units were also analysed in a randomised order, to characterize particles equal to and below 50 µm down to 1 µm. For this purpose, every filter had to be analysed twice: first, with the Raman microscope set up for the size range 10–50 µm, where all particles were measured (20× magnification objective). Secondly, the filter was analysed for particles of the size range 1–10 µm (100× magnification objective), with larger particles being excluded by the software. As particle counts usually increase exponentially towards smaller sizes, it is impossible to measure all particles anymore. For that purpose, the Random Window Sampling algorithm was applied. The procedure is presented in detail elsewhere [ 29 ]. With this approach, a small part of the whole filter surface was analysed by image recognition and subsequent Raman measurements by analysing randomly chosen windows successively. The software extrapolates the total number of particles in the 1–10 µm size range from all window results. The number of concentration values and blanks’ composition can be found in the SM (Tables S.7 and S.8). As the Raman microscope’s capacity is limited to an amount of about 3000 particles within 20 h, the precision of any result obtained with this approach is bound to the measurement time one is willing to spend for the analysis. The extrapolation factor resulting from the proportion of the measured filter area also defines the step size for counting, which could not undercut the lower three-digit range due to the chosen measurement time per sample. Due to this limited precision consistent with the choice of applicable measurement times (max. 24 h per sample), the particle counts within the size range 1–10 µm ranged between 500 and 1269, with a median of 807. The average value of PET particle counts within the size range 10–50 µm ( n  = 6) is 25 with a RSD of 32%. Due to its relation to this lower average value (when compared to > 400 PET particles found in the context of the studies presented above), the RSD basically has a rather limited comparability to the uncertainty of 12% resulting from the homogeneity study. The PET particle size distribution of the allocated units can be found in Figure S.3 .

The PET particle size distribution in the size range of 1–1000 µm can be derived by combining the results from the evaluation of small particles’ content and homogeneity assessment. The particle counts for the size range 1–30 µm and those for the size range 30–1000 µm from the homogeneity study are presented side by side in Fig. 6 .

PET particle size distribution in the candidate RM units assigned to both evaluation of small particles’ content and homogeneity. The number of particles in the size range 1 – 10, 10 – 20 and 20 – 30 µm are referred to the left axis; the number of particles of the size 30 – 1000 µm - to the right axis

It is worth noticing that the number of PET particles in the size range of 30–50 µm fits the pattern presented by all other units of the material, assigned to homogeneity, stability and evaluation of small particles’ content. The ‘zoom-in’ part of the size distribution, presenting only the size bins 30–40 µm and 40–50 µm, is shown in Figure S.4 (SM).

Presence of non-PET particles

Despite all the measures taken to prevent cross-contamination with non-PET particles, each unit of the candidate RM material contains ‘foreign’ particles, which are made either of other polymers (PS, PE, PP, PTFE etc.) or of natural origin materials, i.e. cellulose, skin, CaCO 3 etc. Techniques facilitating chemical identity recognition, particle counting and sizing consequently enable a resolution in this regard. ‘Pure’ counting and sizing techniques (optical microscopy, particle counters etc.) cannot confirm an unchanged composition between single units of the candidate RM regarding the involved bulk material.

Another aspect related to the presence of non-PET particles in the candidate RM is the mass control of PET. Considering the mass of microplastics being a potential measurand in a newly designed RM, it must be considered that non-PET particles might contribute to the total mass of the particles filtered out of the reconstituted water sample. We decided to estimate how much the ‘foreign’ particles would contribute to the total mass of PET particles per unit. Raman microspectroscopy (coupled with suitable software) enables not only measuring the size (Feret diameter) or area of individual particles but also an (manually driven and optically based) estimation of their thickness. Table S.9 (SM) shows examples of non-PET particles recognized in the candidate RM units allocated to homogeneity.

Based on the information from Table S.1 (SM) and using an average density value for each recognized polymer (adopted from [ 38 ]), we were able to approximate an average mass of non-PET particles per unit ( n  = 8), as presented in Table 2 . The density of dust particles was set as 1.87 g/cm 3 , following [ 39 ]. As it can be concluded, the average mass of both not-PET polymer and dust particles per unit is barely 0.25% of the average mass of PET particles. Certainly, it might be possible to determine the contribution of other polymers (other than PET) to the total particle mass per unit. However, it would require an advanced technique such as pyrolysis-GC/MS, TED-GC/MS etc. On the other hand, due to a diverse signal intensity, the total mass of non-PET particles with respect to the mass of PET makes the analysis very difficult.

Non-PET particles of natural origin (Table S.1, SM) comprised a notable population in the candidate RM units, and their presence is inevitable. They mainly originate from sources like paper (cellulose), human skin, Earth’s crust or tap water droplets. Although the availability of both maximum and minimum Feret diameter and, even more relevant, the projection area of each particle, the absence of information on the thickness considerably complicates the estimation of their total mass. In view of their low density (tissue: 0.25–0.50 g/cm 3 , paper 0.5–0.8 g/cm 3 [ 40 ]), their contribution to the total particle mass is negligible.

Conclusions and prospects

Certified reference materials with microplastics applicable for any method of quantifying all particles with a specific chemical identity are not yet available. For a certification procedure of a candidate reference material, accepted validated methods are inevitable. However, for the validation of methods, suitable reference materials would be very useful. We have demonstrated that the candidate RM presented here fulfils the definition of a non-certified reference material, since the assessment of homogeneity and stability (both transport and storage) was satisfactory with respect to the number of PET particles and their size distribution. However, the possibility of developing a CRM based on this material, with a certified value of the microplastics’ number concentration, is still limited. At first, an appropriate lower size limit must be selected; this was not trivial considering the high population of small-sized particles typically present in the samples. The evaluation of particle size distribution in the stock suspension showed indeed a significantly lower number of particles in the size range of 20–40 µm, but they were not eliminated. Moreover, a contribution from the particles of the size range 1–10 µm to the total count was substantial. Taking into account all particles of the size above 30 µm, the average particle number in the units assigned to homogeneity was assessed with a relative standard deviation of 12.1%. As only low PET particle numbers in the size range between 20 and 40 µm were observed, the contribution of the particles of a size close to the cut-off diameter (e.g. 30–31 µm) is negligible. The uncertainty of size determination based on the image resolution itself (~ 1 µm) has, therefore, only a marginal impact on the counts (0–2 particles referred to the size range 30–400 µm). Transport stability assessment proved no significant deviation between the assigned units, neither for the total count nor for the size distribution of PET particles. Moreover, the candidate RM appeared stable at room temperature. We also indicated the capabilities required for a proper determination of microplastics in a water matrix, with respect to participation in RM assessment—in particular the simultaneous determination of size expressed in a certain way, automatic particle counting within the selected size range and recognition of the chemical identity of each particle. It has been shown that Raman microspectroscopy combined with appropriate software (for chemical identification, sizing and counting of particles) is suitable without restriction for this purpose. An additional ability to determine the particle thickness, along with its size and area, could enable an estimation of the contribution of non-PET particles to the total volume (or mass) of particles per unit. In conclusion, this candidate reference material could become another step further in the iterative approach towards certification of the microplastics’ number concentration in a water matrix. Along with the property value assignment, as required in the certification process, the traceability statement must be provided, which—in the case of this specific type of materials—will be an additional challenge. Therefore, a stepwise solution, i.e. sequential improvements of both candidate RMs and analytical methods, is the most suitable strategy.

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Open Access funding enabled and organized by Projekt DEAL. This work received financial support from the Federal Ministry of Education and Research, Germany (BMBF) for the JPI Oceans project HOTMIC (grant number: 03F0851B).

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Oliver Jacob and Elżbieta Anna Stefaniak share first authorship.

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Institute of Water Chemistry, Chair of Analytical Chemistry and Water Chemistry, Technical University of Munich, Lichtenbergstr. 4, 85748, Garching, Germany

Oliver Jacob, Martin Elsner & Natalia P. Ivleva

Joint Research Centre (JRC), European Commission (EC), Geel, Belgium

Elżbieta Anna Stefaniak, John Seghers, Rita La Spina, Konstantinos Chatzipanagis, Andrea Held, Håkan Emteborg & Robert Koeber

Joint Research Centre (JRC), European Commission (EC), Ispra, Italy

Gabriella F. Schirinzi

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OJ and EAS contributed equally to this work including interpretation of results and prepared the draft of the manuscript. OJ worked on all aspects concerning Raman-based analysis under supervision of NPI and contributed to interpretation of results. EAS, JS, AH, HE and RK developed a concept of the candidate reference material and contributed to discussing the results and reviewing the manuscript. JS and HE processed the batch of the candidate reference material and developed in-house methods for homogeneity and processing control. RS and GFS prepared and analysed the samples of pristine PET particles with Raman microscopy and contributed to interpretation of the results. KC prepared and analysed pristine bulk PET material with FT-Raman and contributed to interpretation of the results. RK and ME contributed to the concept development and reviewing of the manuscript. NPI contributed to concept development, reviewing and editing.

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Correspondence to Natalia P. Ivleva .

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Jacob, O., Stefaniak, E.A., Seghers, J. et al. Towards a reference material for microplastics’ number concentration—case study of PET in water using Raman microspectroscopy. Anal Bioanal Chem (2024). https://doi.org/10.1007/s00216-024-05251-7

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Received : 29 December 2023

Revised : 23 February 2024

Accepted : 04 March 2024

Published : 28 March 2024

DOI : https://doi.org/10.1007/s00216-024-05251-7

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