ELECTRON-CAPTURE GAS-CHROMATOGRAPHIC DETERMINATION OF ALKYL THIOPHOSPHATES AS PENTAFLUOROBENZYL DERIVATIVES

An improved and sensitive gas chromatographic method has been establis hed for the determination of four dialkyl thiophosphates including dim ethyl phosphorothioate, diethyl phosphorothioate, dimethyl phosphorodi thioate and diethyl phosphorodithioate. The method is based on the der ivatization of the thiophosphates with pentafluorobenzyl bromide, usin g hexadecyltrimethylammonium bromide as a phase transfer catalyst. The resulting derivatives were separated on an SE-54 capillary column and detected by an electron-capture detector. Several parameters affectin g the derivatization of the related thiophosphates were investigated. Determinations of the thiophosphates were attainable at pmol levels. T he detection limits (signal to noise ratio of 5) of dimethyl phosphoro thioate, diethyl phosphorothioate, dimethyl phosphorodithioate and die thyl phosphorodithioate in aqueous sample were at about 8.3, 6.0, 5.7 and 5.6 nM, respectively. Application of the method to the analysis of the thiophosphates spiked in plasma, after simple ultrafiltration tre atment, proved to be feasible.