Mass spectrometry (MS) has played a role in every research project in my scientific career. This presentation will take the audience on a tour of selected projects over the past 20 years. Early studies used selected ion monitoring gas chromatography MS. A study of chlordane compounds in ambient and indoor air samples from the Great Lakes and corn belt, respectively, revealed cis-chlordane enantiomer signatures were nearly racemic across all sampling locations, while trans-chlordane was slightly enriched in the (-) enantiomer in outdoor air, but racemic in indoor air. Heptachlor epoxide, a metabolite, was more highly enriched in the (+) enantiomer in outdoor air, likely due to biological processes. A dosing study with rats investigated both the concentration and enantiomer profiles of α-hexachlorocyclohexane in several tissues. Enantiomer signatures in blood were nearly racemic, enriched in the (-) enantiomer in liver, slightly enriched in the (+) enantiomer in fat, and highly enriched in the (+) enantiomer in brain, where enantioselective transport across the blood-brain barrier is likely a factor. A study of chlordane in sediments showed that cis- and trans-chlordane were slightly enriched in (+) and (-) enantiomers, respectively, with shallow and suspended sediments having similar enriched enantiomer signatures to soil, a likely source of the pollutants. In aquatic environmental systems, enantiomer signatures in 98% of fipronil, 82% of bifenthrin, and 43% of cis-permethrin samples were racemic, while exposed fish had non-racemic signatures [(-) enriched] of bifenthrin in 67% of samples, likely due to enantioselective biological processes. These studies lend evidence to the type and degree of degradation of contaminants in the environment and biological systems. Recently, liquid chromatography with high-resolution MS was employed to conduct nontargeted analyses. The EPA’s Non-Targeted Analysis Collaborative Trial uses mixtures of ~1,300 compounds to provide a benchmark for suspect screening performance. Unblinded analysis of ten mixtures revealed true positive rates ranging from 20-65% after adjusting for isomers. As shown by these studies and proclaimed by Dr. Hites, mass spectrometry is far too important to be called a spec(k).

Don’t call it a spec(k)

2019 Spring National Meeting

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