Negative ion electrospray mass spectrometry of aminomethylphosphonic acid and glyphosate: elucidation of fragmentation mechanisms by multistage mass spectrometry incorporating in-source deuterium labelling.

Glyphosate and its main metabolite, aminomethylphosphonic acid, introduced by direct infusion in (2)H(2)O, appear in negative ion electrospray mass spectrometry (ES-MS) as triply deuteriated [M[bond]H](-) ions. Sites of deuterium residence and loss were established using the multistage (MS(n)) capabilities of an ion trap mass spectrometer to assist in the determination of fragmentation mechanisms. The study reveals specific mechanisms, common to each analyte, such as those involving a five-membered transition state between the amine and phosphonate group, as well as analyte specific transitions. Copyright 2003 John Wiley & Sons, Ltd.