GC Hands-on Laboratory Experiments

Fatty Acid Methyl Ester (FAME) experiments are excellent experiments for addressing principles and techniques of gas chromatography. FAME can have a number of applications, including:

the analysis of saturated, unsaturated, and monounsaturated fats in food products;
identifying and differentiating microorganisms; and
understanding energetics in organisms.

FAME can also facilitate a student's understanding of a number of techniques, including:

acid digestion in organic materials;
extractions of aqueous solutions; and
organic derivatization reactions.

The AOAC Official Method 996.01 is a particularly good FAME which uses cereal products as the context.

2. Analysis of Petroleum Waxes - Analysis by Gas Chromatography

This method, offered by ASTM, will test the student s ability to follow an industrial standard method. It may involve:

installing column,
setting flows,
calculation of theoretical plates,
resolution as well as calculating the mass % for each carbon number determined from an internal standard,
calculating the mass % of each normal paraffin hydrocarbon from individual areas using an internal standard.

The student then must see if the repeatability of each test falls within the range set by the standard.

This method is for intermediate to advanced students, however a professor may have inexperienced students perform column installation and setup while the more advanced students perform the analysis. Also the method may be modified according to the professor's own needs.

Materials should be easily accessible to professors. Any wax candle will do. These waxes may be diluted in other solvents like toluene or xylene if cyclohexane is not available.

Two experiments are included which use gas chromatography (GC) as a tool to measure the concentration of reactants and products.

By conducting the first experiment, the learner will determine when equilibrium is attained in a chemical system.
By conducting the second experiment, the student will determine the shift in equilibrium in the same system.
A discussion of chemical equilibrium including Le Chateliers Principle is included.

These experiments are best introduced after the students have already used GC and are familiar with quantitative as well as qualitative techniques.
Using the experimental data as a basis for a continued discussion on equilibrium, the instructor can use a spectrophotometric analysis to study the effect of temperature on equilibrium.

4. Quantitative Analysis by Gas Chromatography

This experiment is best suited for a student's first exposure to a gas chromatograph, typically occurring during the second week of class.

The two-part laboratory sequence consists of performing an experiment involving commercial paint solvents. In part A, students will determine retention times of some standard pure substances. In part B, students will prepare chromatograms of unknowns.

Using the outputs of these two phases, students will draw analogies to the components of a gas chromatograph and a typical analysis.