ANALYSIS OF ORGANOPHOSPHORUS PESTICIDE-RESIDUES BY LOW-ENERGY TANDEM MASS-SPECTROMETRY USING ELECTROSPRAY-IONIZATION

Electrospray mass spectrometry has aided the structural characterizati on of a series of phosphorothioates and phosphorodithioates as a means of developing a new method for detection of these organophosphorus pe sticides. Possible fragmentation routes were first obtained by cone vo ltage 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 fragmenta tion for all investigated pesticides and also permitted differentiatio n of isomeric phosphorodithioates. MS/MS product and precursor ion spe ctra of selected intermediate fragments provided additional structural data and allowed rationalization of the fragmentation routes. Electro spray MS has proved to be a specific and very sensitive method for cha racterization of organophosphorus pesticides and allowed detection at levels as low as 10 mu g/g.