MICROANALYSIS OF DIALKYLPHOSPHORUS METABOLITES OF ORGANOPHOSPHORUS PESTICIDES IN HUMAN BLOOD BY CAPILLARY GAS-CHROMATOGRAPHY AND BY PHOSPHORUS-SELECTIVE AND ION-TRAP DETECTION

A procedure for the determination of dialkylphosphorus metabolites of organophosphorus pesticides in human blood has been worked out. Dimethyl and diethyl phosphates, phosphorothioates and phosphorodithioates, extracted with diethyl ether from plasma acidified with hydrochloric acid, were methylated with diazomethane and analysed by capillary gas chromatography with an alkali flame ionization detector and an ion trap detector. The extraction of metabolites was preceded by n-hexane extraction of parent organophosphorus pesticides without a negative effect on the efficiency of metabolite extraction. If plasma samples, containing 2 mu g/ml of each metabolite, were not saturated with sodium chloride before extraction, only dialkyl phosphorothioates were recovered by more than 80%. The recoveries of other metabolites were less than 25%. The extraction of plasma samples saturated with sodium chloride resulted in higher recoveries of all metabolites. At concentrations ranging from 0.2 to 2.8 mu g/ml the accumulation efficiencies (% +/- S.D.) of dimethyl and diethyl phosphorothioates were 92 +/- 20 and 97 +/- 11, and those of corresponding phosphorodithioates 79 +/- 7 and 71 +/- 4. A significantly lower recovery (36 +/- 12%) was determined for dimethyl phosphate at concentrations in plasma below 2 mu g/ml. The recovery of diethyl phosphate was dependent on the initial metabolite concentration in plasma being 31 +/- 5% at concentrations lower than 0.5 mu g/ml, 51 +/- 12% at concentrations ranging from 0.7 to 2.7 mu g/ml and 97 +/- 3% at concentrations at or above 2 mu g/ml. Detection limits of metabolites in plasma using the phosphorus selective detector were 150 ng/ml for dimethyl phosphate and 50 ng/ml for other metabolites. Those values were for dialkyl phosphates and phophorothioates three to five times lower and for dialkyl phosphorodithioates even 30 times lower than the detection limits achieved by the use of ion trap detector. The procedure was applied for the evidence and confirmation of human poisoning with organophosphorus pesticides.