Methanol chemical ionization quadrupole ion trap mass spectrometry of O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothiolate (VX) and its degradation products

Mass spectrometric analysis of O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothiolate (VX) degradation products by electron ionization produces extensive fragmentation with little or no molecular ion information making product identification difficult. Milder chemical ionization (CI) is commonly used to provide molecular mass and structure confirmation. In this study, methanol was used as a CI reagent in combination with an ion trap detector for detection and identification of over 30 compounds present in a thermally degraded sample of VX. The use of methanol provides superior results for this class of compounds with less fragmentation than commonly observed with gas reagents and offers logistical advantages for on-site analysis by being easier to transport and safer to use than gas cylinders.