Reactions of vinyl chloride and methanol in a quadrupole ion trap mass spectrometer during VOC analysis

A reaction between vinyl chloride and the solvent (methanol) was observed d uring volatile organic compound (VOC) analysis on a gas chromatograph/quadr upole ion trap mass spectrometer (GC/MS). A chromatographic peak at a reten tion time consistent with vinyl chloride produced a mass spectrum without t he characteristic chlorine isotope ions m/z 62 and 64 but instead contained an apparent molecular ion, mit 58. The mit 58 ion is not found in the refe rence spectrum of vinyl chloride. This spectrum was observed when methanol was used as solvent in internal standard, surrogate standard, or analyte so lutions. Subsequent VOC standard analysis indicated that the abundance of t he m/z 58 ion was directly proportional to the amount of vinyl chloride in the water samples. The correct spectrum for vinyl chloride was observed (m/ z 62 and 64) when no methanol was added. From these experiments, we conclud ed that a reaction was occurring between the vinyl chloride and methanol in the ion trap producing a new species with a molecular ion at m/z 58. When ethanol was used as the solvent for the internal standard solution or surro gate standard, a correct spectrum of vinyl chloride was obtained.