The University of Montana received funding from the National Science Foundation CCLI program in 2004 to implement gas chromatography-mass spectrometry (GC-MS) exercises throughout the undergraduate curriculum. As part of that project, new GC-MS laboratory exercises for the General, Organic and Biochemistry laboratory (CHEM 154) and for the Instrumental Analysis laboratory (CHEM 342) have been developed and implemented. The handouts for these exercises are made available here so that they can be adapted and implemented in other programs.

CHEM 154 GC-MS Exercise
Pairs of students perform a base hydrolysis reaction with corn oil, then make methyl esters of the fatty acids. Samples are run on the GC MS over-night using the autosampler, and students are provided with the chromatogram for their own sample. The spectrum for one peak is selected and provided to all students. The spectrum for the closest NIST match is also provided. Students circle the peaks that differ between sample and NIST spectra. Questions about the CHEM 154 exercise and its implementation should be directed to Dr. Holly Thompson .

CHEM 342 GC-MS Exercise
In Part I of this exercise, students are provided with a mixed standard of toluene, xylenes, chlorobenzene, dichlorobenzene, bromobenzene and dibromobenzene in pentane. The students develop an optimized separation of these compounds, and analyze an unknown mixture containing 2 to 4 of the compounds in the standard. Students must identify all compounds in the standard mixture from the mass spectra, identify the compounds in the unknown from retention time and mass spectrum, and quantify the compounds in the unknown using the known concentrations in the standard mixture. This exercise serves as an excellent introduction to GC analysis and MS analysis and spectral interpretation.

Part II of this exercise has a 'real world' connection to forensic arson analysis, and also generates significant discussion about the composition of various fuels. Students analyze samples of various fuels or accelerants (gasoline, kerosene, charcoal lighter, paint thinner, lacquer thinner, and Coleman fuel) dissolved in pentane. The components are separated using a pre-optimized temperature program. The students are expected to observe and discuss what the elution temperature range indicates about the accelerant. They utilize the selected ion monitoring feature of the GC/MS to generate and interpret profiles of aliphatic (m/q 57), alkylbenzene (m/q 91), and naphthalene (m/q 128) compounds, which allows the students to distinguish between most accelerants with a high degree of confidence based on the elution pattern and the presence or absence of aromatic compounds. The students then utilize the patterns to identify the accelerant in an unknown. This is a very instructive exercise from the standpoint of demonstrating the capabilities of the GC/MS instrument, and also from the standpoint of the students' knowledge of and interest in the composition of various fuels and solvents. Questions about the CHEM 342 exercise and its implementation should be directed to Dr. Chris Palmer .

This research was supported by an award from the National Science Foundation (DUE-0411293).