LCGC Blog: Why Should We Learn (and Teach) Chromatography?

As I prepare to teach for a new semester, I have been thinking about the concepts I would like my students to learn about chromatography and separation methods for analytical chemistry. I have been an instructor and lecturer on these topics for many types of audiences. These audiences are usually undergraduates or graduate students but have also been high school students or professionals from academic, industrial, or government settings. When I first meet with these groups, one question I try to address immediately is “Why should I learn this topic?” The following list includes some general strategies I have used over the years to answer this question and to explain why an understanding of chromatography and related methods is important in analytical chemistry and in addressing important issues and questions in today’s world.

Chromatography as a key component of chemical analysis: The first reason for learning and teaching about chromatography is the important role this plays in analytical chemistry for the separation and analysis of complex samples. This instructional format makes sense given the prevalence of gas chromatography (GC), high performance liquid chromatography (HPLC) and related methods, such as gas chromatography mass spectrometry (GC–MS) and liquid chromatography (LC–MS) in academic, government, and industrial laboratories. However, discussing chromatography this way tends to emphasize its use as a tool rather than providing a fundamental understanding of how it works or could be adapted to new applications. Combining these lectures with a lab is one way students can get a better appreciation for chromatographic methods and how they work.

Chromatography as an illustration of the importance of analytical chemistry: A second reason chromatography is important in the classroom is it can be used to illustrate the overall importance of analytical chemistry. This discussion can flow naturally from the widespread use of chromatography and related separations in areas such as drug development, environmental analysis, food science, forensics, clinical chemistry, biomedical research, and materials characterization. The impact of chromatography can be further demonstrated through historical examples and by having students do reports or presentations on how chromatography and chemical separations have been used in a field in which they are interested or wish to pursue in their careers.

Chromatography as an example to describe a chemical analysis: A third reason chromatography is important to teach is it can be used to illustrate general approaches for data analysis and analytical method validation. For example, this can be done by using the results from a chromatographic method to discuss and illustrate the concepts of accuracy, precision, signal-to-noise ratios, detection limits, linear and dynamic ranges, and selectivity. The creation and use of internal standards, linear regression and calibration curves are also items that can be easily introduced and demonstrated in this way. Statistical methods for comparing and evaluating data, such as the Student’s t-test, can also be included as part of this discussion.

Chromatography as an introduction to other separation methods: A fourth reason for the importance of chromatography is it can be used as a teaching platform to discuss other separation methods. To do this, I start with the idea of chromatography being both a phase- and rate-based method, in that it separates sample components as they distribute between two phases (the mobile phase and stationary phase), which leads to different rates of travel for the applied components as they pass through the chromatographic system. I then discuss extractions, as an example of a simple phase-based separation, and then move to more complex variations such as a countercurrent extraction, which can be used as a model for chromatography. From here, I then proceed to lectures on the various types of chromatography, moving from GC and LC to SFC, among other forms. In a similar way, I use the fact that chromatography is also a rate-based separation to then examine separation methods that use external fields instead of phase equilibria to provide different rates of travel for analytes, as occurs in electrophoresis and field flow-fractionation.

Chromatography as a tool to discuss fundamental chemical and physical principles: For advanced courses, a fifth reason chromatography is valuable in teaching is as a means to discuss important physical and chemical concepts students may not have covered in their earlier classes. A good example of this is the topic of intermolecular interactions (e.g., non-polar and dipole-related interactions, hydrogen bonding, ionic interactions, etc.), which are important in affecting properties such as chemical volatility, solubility, and solute interactions with the stationary phase and mobile phase in a chromatographic system. Additional concepts that chromatography can be useful in discussing are phase equilibria, diffusion, mass transfer, flow profiles, and the effects of support structure on flow and solute transport. Although these topics are often not discussed in other classes, especially at the undergraduate level, they are important in understanding the behavior of chromatography and many other separation methods.

Chromatography as an introduction to hybrid techniques and other analytical methods: For students who are learning about instrumental analysis, chromatography is further valuable as an instructional tool in introducing the idea of hybrid methods, which combine the features of two or more distinct techniques for chemical analysis. This can be illustrated with GC–MS and LC–MS. This topic also opens a way to discuss multi-dimensional methods such as 2D-GC, 2D-LC, and isoelectric focusing/ sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE). These hybrid methods can further be used to introduce students to the other techniques used in these combinations. This may include discussions on electrophoresis and mass spectrometry, as well as various forms of spectroscopy.

In summary, I have found there are numerous reasons why chromatography and separation methods are valuable topics for learning and instruction. The ways these methods may be used in this setting can span from a discussion of chromatography as a tool for separations and analysis to the use of chromatography to discuss other concepts and methods in analytical chemistry and separation science. The route that is selected for instruction will depend on the target audience and the goals of the course or lecture. However, I believe this list illustrates how chromatography can be used in many ways to instruct students and others on key topics in the field of analytical chemistry and on the importance of chemical analysis and separations to address ongoing needs in the world around us.