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

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

Janelle L. Torres y Torres *, Shauna L. Hiley , Steven P. Lorimor , Jonathan S. Rhoad , Benjamin D. Caldwell , Gerald L. Zweerink , and Michael Ducey

Chemistry Department, Missouri Western State University, St. Joseph, Missouri 64507, United States

J. Chem. Educ., 2015, 92 (5), pp 900–902

DOI: 10.1021/ed500977r

Publication Date (Web): April 14, 2015

Copyright © 2015 The American Chemical Society and Division of Chemical Education, Inc.

Supporting Documents (17 pages) include the student experiment handout, notes to instructor, and retention times for GC results for 9 different types of beverages.

ABSTRACT: http://pubs.acs.org/doi/abs/10.1021/ed500977r

This paper by chemistry faculty describes a series of experiments designed to analyze the caffeine content of a commercial beverage product using a suite of instrumentation equipment.  The CAP series (Characterization and Analysis of a Product) involves a sequence of 5 experiments (CAPs 1 – 5) that General College Chemistry students conduct throughout the first semester.  Different beverage products that can be used include coffee, tea, soft drinks, or energy drinks.

CAP Experiment 1

·         The students examine the packaging and the contents of the container and note qualitative and quantitative observations.  They are then asked to come up with testable questions about the product including the packaging.

·         This part is done during the first week of the lab.

·         Students get to practice using vocabulary terms and applying the scientific method.

·         For each part of the CAP experiments, students work in groups of 3-4.

CAP Experiment 2

·         The goal of this experiment is to identify caffeine in the extract along with other compounds like flavoring agents using GC-MS and TLC.

·         Chemistry concepts covered in this experiment include: polar/nonpolar extraction through extraction, GC, TLC, and atomic structure and isotopes (chlorine peaks in mass spectra).

·         This takes at least 2 3-hour lab sessions, probably best after discussion of atomic mass and IMF.

·         See paper for the specific procedures described for the extraction process and the GC-MS and TLC analysis.

·         Reagents used: sodium carbonate, dichloromethane, caffeine standard in dichloromethane, methanol/ethyl acetate (HPLC grade solvents)

CAP Experiment 3

·         FT-IR analysis for caffeine and other components.

·         Not described in this paper.

CAP Experiment 4

·         Atomic absorption spectroscopy

·         Not described in this paper

CAP Experiment 5

·         Students design an experiment to test their testable question or hypothesis formulated in CAP Experiment 1.  This might include instrumentation use as well.

·         Not described in paper.

HAZARDS

·         The authors provide some safety precautions regarding reagent use and procedural steps.  Hazard warnings are given for the reagents used.

RESULTS AND DISCUSSION

·         The caffeine, a white powder in pure form, may come out slightly discolored a light yellow or beige.

·         TLC using the prescribed solvent was sufficient to resolve caffeine from vanillin.

·         Vanillin was identified by its mass spectrum.

·         For the GC−MS experiment, students record information for each compound identified to an 80% or better match to the spectral library, including the compound name, scan number, retention time, the library reference spectrum number, and the percent identity or “quality” of the match.

·         Students use the mass spectrum to observe the peaks for chlorine isotopes and calculate percent abundance of each.