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. Dimeth yl and diethyl phosphates, phosphorothioates and phosphorodithioates, extracted with diethyl ether from plasma acidified with hydrochloric a cid, were methylated with diazomethane and analysed by capillary gas c hromatography with an alkali flame ionization detector and an ion trap detector. The extraction of metabolites was preceded by n-hexane extr action of parent organophosphorus pesticides without a negative effect on the efficiency of metabolite extraction. If plasma samples, contai ning 2 mu g/ml of each metabolite, were not saturated with sodium chlo ride before extraction, only dialkyl phosphorothioates were recovered by more than 80%. The recoveries of other metabolites were less than 2 5%. The extraction of plasma samples saturated with sodium chloride re sulted in higher recoveries of all metabolites. At concentrations rang ing from 0.2 to 2.8 mu g/ml the accumulation efficiencies (% +/- S.D.) of dimethyl and diethyl phosphorothioates were 92 +/- 20 and 97 +/- 1 1, and those of corresponding phosphorodithioates 79 +/- 7 and 71 +/- 4. A significantly lower recovery (36 +/- 12%) was determined for dime thyl phosphate at concentrations in plasma below 2 mu g/ml. The recove ry of diethyl phosphate was dependent on the initial metabolite concen tration 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 o f metabolites in plasma using the phosphorus selective detector were 1 50 ng/ml for dimethyl phosphate and 50 ng/ml for other metabolites. Th ose values were for dialkyl phosphates and phophorothioates three to f ive times lower and for dialkyl phosphorodithioates even 30 times lowe r than the detection limits achieved by the use of ion trap detector. The procedure was applied for the evidence and confirmation of human p oisoning with organophosphorus pesticides.