Fragmentation and reactions of organophosphate ions produced by electrospray ionization

Electrospray ionization of some organophosphate esters has been studied in both an LCQ (TM) ion trap mass spectrometer and a VG Quattro II (TM) triple quadrupole mass spectrometer. The structures and fragmentations of the ions have been investigated by CID experiments with up to MS4 being performed in the ion trap. There is a difference in the CID of the protonated methyl esters compared with that of the ethyl and isopropyl esters with the former eliminating methanol and the latter alkenes. Use of partially deuterated dimethyl methylphosphonate has allowed the observation of the migration of a methyl group from the phosphorus to the oxygen of a P-O bond. A process which we describe as a 'pseudometastable decay' of an ion has also been observed. (C) 1997 Elsevier Science B.V.