title: Analysis of O,S-dimethyl hydrogen phosphorothioate in urine, a specific biomarker for methamidophos.
abstract: A rugged and sensitive method was developed to monitor urinary concentrations of O,S-dimethyl hydrogen phosphorothioate (O,S-DMPT), a specific biomarker of exposure to the organophosphate insecticide methamidophos. After pH adjustment and C18 solid phase extraction column cleanup, the urine was lyophilized at a low temperature to prevent loss of possibly highly volatile and unstable O,S-DMPT metabolite. The dried residue was derivatized using N-methyl-N-(tert-butyldimethylsilyl)trifluoroacetamide and 1% tert-butyldimethylchlorosilane (MTBSTFA + 1% TBDMCS) in acetonitrile. After it was filtered, the derivatized product was analyzed and quantified by gas chromatography using a pulse flame photometric detector specific for phosphorus compounds. The limit of detection for this method was 0.004 ppm with a limit of quantitation of 0.02 ppm of urine. The mean recovery value for O,S-DMPT from 17 urine samples fortified at varying concentrations was 108% with a standard deviation of 12%.
mesh_terms: D015415:Biomarkers / Q000652:urine*; D002849:Chromatography, Gas; D003080:Cold Temperature; D004781:Environmental Exposure; D005612:Freeze Drying; D006863:Hydrogen-Ion Concentration; D007306:Insecticides; D009946:Organothiophosphorus Compounds / Q000652:urine*
chemical_list: D015415:Biomarkers; D007306:Insecticides; C478498:O,S-dimethyl hydrogen phosphorothioate; D009946:Organothiophosphorus Compounds; C014655:methamidophos