Field Desorption Mass Spectrometry of Standard Organophosphorus Pesticides and Their Identification in Waste Water

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Abstract
The characteristic behavior of 4 groups of commonly used organophosphorus pesticides (phosphates, phosphorothionates, phosphorothiolates and phosphorodithioates) was investigated by field desorption mass spectrometry. Their spectra show molecular ions of high abundance and characteristic fragmentation patterns. The phosphates and phosphorothionates usually showed the .alpha.-cleavage with respect to the P atom with and without proton transfer. The phosphorothiolates and phosphorodithioates usually showed the .beta.-cleavage from the P atom. The fragments with the charge retention on the P moiety were also observed in the field desorption mass spectra, although their abundances were often relatively low. Analyses of standard mixtures and some waste water samples indicated that field desorption mass spectrometry was suitable for the identification of organophosphorus pesticides at nanogram levels in mixtures and environmental samples without preliminary separation and purification.