Benefits and Malefits of Solvent Vent Mode in Combination with Tandem Mass Spectrometry for Static Headspace Analysis of Organic Solvents by Gas Chromatography

Static headspace analysis is of value for the detection of volatile compounds present in biological and environmental samples in trace amounts. However, trace compound detection has typically relied on splitless inlet mode which generates wide non-Gaussian peaks when using ordinary methylpolysiloxane columns without resort to specialty columns such as those using a polyethylene glycol stationary phase for alcohols. Solvent vent settings were investigated as an alternative approach that would enable large volume injections necessary for high sensitivity. This inlet configuration was supported by tandem quadrupole mass spectrometric compound detection which provided low backgrounds and limited extraneous compound interference. The method was studied with diverse compounds of toxicological significance, including phosphine, dioxane, dichloromethane, ethyl acetate and simple alcohols such as methanol, ethanol, and isopropanol. Despite differences in initial temperature settings for inlet and oven required by each of these analytes, Solvent vent mode in each case introduced significant advantages in terms of chromatographic peak shape, separation, and sensitivity. Most significantly, the method enabled separation of methanol, ethanol, and isopropanol in contrast to Splitless mode which resulted in significant compound overlap. The effects of changes to crucial gas chromatographic and Solvent Vent parameters were investigated including injection volume, helium carrier gas flow rate, applicability to quantitation, injection needle dwell time, needle residence time, carryover, headspace incubation temperature, oven and inlet temperatures and timing of GC oven temperature ramping. A proof of principle was developed involving analyses of complex fire accelerants gasoline and carburetor cleaner where ~ 30 peaks could be separated from one another by application of the espoused principles.