Analytical Method for the Determination of Urinary Alkylphosphates in Subjects Occupationally Exposed to Organophosphorus Pesticides and in the General Population

The determination of urinary alkylphosphates monitors occupational exposure to organophosphorus pesticides and insecticides. This paper describes a method for the quantitative determination of the following metabolites: O,O-dimethylphosphate (DMP), O,O-diethylphosphate (DEP), O,O-diethyldithiophosphate (DETP), O,O-dimethyldithiophosphate (DMDTP), O,O-diethyldithiophosphate (DEDTP), and O,O-dimethylthiophosphate (DMTP). The compounds are derivatized with pentafluorobenzylbromide into pentafluorobenzyl esters which are determined by gas chromatography with a capillary column of intermediate polarity and a flame photometric detector specific for phosphorus. Before the analytical gas chromatographic stage, the urinary extracts are purified on isolute SPE CN columns. The proposed method has a limit of detection of 2-3 micrograms/L at 62.5 micrograms/L and a mean recovery of the purification stage of 85.8-101.0% for all six compounds. The coefficient of variation of the analytical procedure was 7.9-11.9% for the six compounds. The low detection limits make this method suitable also for determining the six metabolites in the general population.