Evaluation of capillary microextraction of volatiles (CMV) coupled to a person-portable gas chromatograph mass spectrometer (GC–MS) for the analysis of gasoline residues

Abstract

A novel dynamic headspace extraction device, the capillary microextraction of volatiles (CMV) was coupled to a person-portable GC–MS for the analysis of ignitable liquid residues (ILR) sampled from simulated fire debris. A benchtop GC–MS was used as a benchmark for the performance of the portable GC–MS. The use of a paper cup in conjunction with the CMV for in-field sampling of the VOCs associated with ILRs is presented for the first time. A five-minute sampling/extraction protocol was sufficient to recover six (6) analytes: toluene, ethylbenzene, m-xylene, o-xylene, 4-ethyltoluene, and 1,2,4-trimethylbenzene from a 0.01 µL spike of gasoline, with typical mass recoveries of 4–24 ng. Extractions from water-logged debris resulted in reliable detection of the same six compounds but up to 62% less was retained relative to dry debris. Recoveries for detected analytes ranged between 1 and 5% at several solution spike volumes suggesting proportional retention by the CMV. The CMV also demonstrated greater extraction capabilities than the portable GC–MS air sampling wand. Out of a 20-component mixture, 17 compounds were detected compared to the wand’s 13, with the majority of these at higher overall intensities for CMV. An overall 21-minute analytical method was developed using the CMV/Cup protocol capable of detecting several ILR-associated compounds at up to 10x greater sensitivity than traditional extraction techniques such as activated charcoal strips and SPME fibers.