Mass spectrometry organophosphorus compounds

Abstract

Chlormephos (S- ch loromethyl-O, O-diethyl phosphorothiolothionate) and Oxychlormephos (O-chloromethyl- O,O-diethyl phosphorothiolothionate) were prepared by the interaction .of their appropriate salts with chlorobromomethane. These compounds and their intermediates were characterized and identified by using elemental analysis, GLC, IR and mass spectrometry. The fate of chlormephos and oxy ~en analogues in soil and in various crops was the main purpose of the present work. As a preliminary to this study however, the stability of these compounds in aqueous medium at various pH were determined. It was found that chlormephos was relatively stable at acid pH but was rapidly degraded in alkaline condition. The oxygen analogue was prepared as this was considered to be a potential metabolites. The fragmentation patterns were estab~ished with the aid of accurate mass measurements and metastable transitions. The mass spectra of these compounds show that most ions arise through hydrogen migrati~n from alkyl ester groups to the phosphorous-oxygen backbone. Th e compounds have been reported t o b e p otentially used as pesticides and have high physio l ogi cal and pesticidal activities. Mass spectrometry is emp loyed to provide information of various fragmentations and breakdown products in order to compare them with the various metabolites expected to be formed under the influence of b'ological , chpmiPRl and environmental conditions and to confirm or characterize the identities of the residues of unknown structures.