Analysis of Organophosphorus Pesticide Residues by Low Energy Tandem Mass Spectrometry Using Electrospray Ionization

Abstract

Electrospray mass spectrometry has aided the structural characterization of a series of phosphorothioates and phosphorodithioates as a means of developing a new method for detection of these organophosphorus pesticides. Possible fragmentation routes were first obtained by cone voltage dissociation. Low energy collision-activated dissociation (CAD) MS/MS analyses of the protonated molecular ion [M+H]⁻ confirmed the characteristic fingerprint patterns obtained by cone voltage fragmentation for all investigated pesticides and also permitted differentiation of isomeric phosphorodithioates. MS/MS product and precursor ion spectra of selected intermediate fragments provided additional structural data and allowed rationalization of the fragmentation routes. Electrospray MS has proved to be a specific and very sensitive method for characterization of organophosphorus pesticides and allowed detection at levels as low as 10 μg/g.