Separation of Caffeine from Beverages and Analysis Using Thin-Layer Chromatography and Gas Chromatography-Mass Spectrometry

The Characterization and Analysis of a Product (CAP) project is used to introduce first-semester general chemistry students to chemical instrumentation through the analysis of caffeine-containing beverage products. Some examples of these products have included coffee, tea, and energy drinks. Students perform at least three instrumental experiments as a part of this five-part project to analyze different components of the beverage and its packaging. In this discussion, the first of these experiments is presented. Caffeine and other components, such as flavorings, are extracted from the product using dichloromethane. The extract is analyzed using thin-layer chromatography (TLC) and gas chromatography mass spectrometry (GC MS) to identify caffeine and other trace components. Students also calculate the percent abundance of the Cl-35 and Cl-37 isotopes from the dichloromethane mass spectrum. These exercises demonstrate several basic concepts introduced in the first-semester course, and are easily adaptable to using in several courses in the undergraduate curriculum.