Capillary column ammonia chemical ionization mass spectrometry of organophosphorus chemical warfare agents and simulants

Abstract

Capillary column ammonia chemical ionization mass spectrometry was investigated as a technique for the characterization of a number of organophosphorus chemical warfare agents and simulants, since electron impact ionization provides little or no molecular ion information for these compounds. The effects of source temperature, source pressure, electron energy and electron emission were investigated in order to optimize ammonia chemical ionization conditions. Source temperature was found to have a dramatic effect on the chemical ionization mass spectra acquired. Abundant [M + NH4]+ and/or [M + H]+ quasimolecular ions were usually observed at lower source temperatures for the selected compounds under positive ion chemical ionization conditions, along with a number of characteristic fragmentation ions. Full-scan mass spectra were obtained for 1--2 ng of analyte during the capillary column ammonia chemical ionization operation. The sensitivity, molecular ion information afforded and lack of background interference ions associated with this technique make it a good candidate for the confirmation of organophosphorus chemical warfare agents and simulants.