The isobaric ions CH3OPO+ and CH3OPNH2+ and their neutral counterparts: a tandem mass spectrometry and CBS-QB3 computational study

In contrast to a previous report [J. Mass Spectrom. 171 (1997) 79], the dissociative electron ionization of acephate does not generate pure m/z 78 ions CH3OPO+. By combining the results of exact mass measurements, (multiple) high energy collision experiments and CBS-QB3 calculations, it is concluded that the m/z 78 ions consist of CH3OPO+ and CH2OPOH+ in admixture with isobaric CH5PON+ ions. A computational analysis of the dissociation …