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Negative chemical ionization mass spectrometry of organophosphorus pesticides
Author(s) -
Stan H.J.,
Kellner G.
Publication year - 1982
Publication title -
biomedical mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0306-042X
DOI - 10.1002/bms.1200091106
Subject(s) - chemistry , chemical ionization , electron ionization , ion , mass spectrometry , mass spectrum , molecule , ionization , polyatomic ion , substituent , analytical chemistry (journal) , organic chemistry , chromatography
The negative ion mass spectra of 52 organophosphorus pesticides obtained by chemical ionization with methane under electron capture conditions are presented. The influence of different ionization parameters on the total ion current as well as the relative intensities of the various fragment ions was investigated. In general, the mass spectra show few fragment ions, but these are characteristic for the chemical class of the compound (phosphate, phosphorothionate, phosphorothiolate, phosphorodithioate). The occurrence of the molecular anion is strongly dependent on the structure of the molecule and its ability to stabilize by charge delocalization the radical formed in the primary electron capture reaction. This takes place particularly in the organophosphorus esters of the parathion group which have an aromatic moiety with an electron attracting substituent. The phosphorothionates of the parathion group form a stable thiophenolate fragment which competes in the stability with the molecular anion. The relative intensity of these two ions in the spectrum is dependent on the ion source temperature. Because of the few, but intense fragment ions formed, negative ion mass spectrometry with multiple ion detection is expected to be a valuable tool for residue analysis in food and environmental samples.