A New GC-MS Experiment for the Undergraduate Instrumental Analysis Laboratory in Environmental Chemistry: Methyl-t-butyl Ether and Benzene in Gasoline

With the recent ACS approval of an option in environmental chemistry at the undergraduate level, there is a need for new experiments that illustrate fundamental principles of instrumental analysis in the context of environmental chemistry. We describe an experiment that utilizes combined gas chromatography-mass spectrometry (GC-MS) in the qualitative and quantitative analysis of methyl tert-butyl ether (MTBE) and benzene in gasoline. This is particularly appropriate, given the increased use of oxygenates in reformulated gasolines in the United States. In addition to illustrating the fundamentals of GC and MS, this experiment demonstrates (i) the use of internal standards to improve precision; (ii) the application of the method of standard additions; and (iii) the importance of techniques such as selected ion extraction/monitoring in the identification and measurement of specific highly volatile organic compounds in complex environmental mixtures.