SOFT - TIAFT 1998 Poster Session 4 Friday October 9, 1998

Fuad A. Tarbah, Bernd Kardel, Susanne Pier, Thomas Daldrup

Institute of Legale Medicine, Heinrich-Heine-University, P.O. Box 10 10 07, D-40001 Duesseldorf, Germany

In this paper we describe a sensitive gas chromatography-mass spectrometry (GC/MS) method for the detection of dimethylphosphate (DMP) in human blood, urine, and gastric fluid. DMP is a stable metabolite of some organophosphate compounds, like mevinphos, dicrotophos, monocrotophos, dichlorvos, phosphamidon and trichlorfon. This procedure can also be used in post-mortem material as heart blood, liver, kidney, muscles, fat tissues and brain tissues.

DMP was extracted with acetonitrile from a 0.1 mL aliquot of the sample. Deuterated dimethylphosphate (DMP-d6) was used as an internal standard. The extract was washed once with 0.02 mL heptane and 0.02 mL water. Then 0.05 mL ethanol was added to the aqueous phase to allow cold evaporation under a stream of nitrogen. 0.2 mL acetonitrile and dry potassium carbonate were added to the residue, followed by 0.01 mL pentaflurobenzyl-bromide (PFB-Br) for derivatization. After incubation for 30 min at 90°C, 0.05 mL of the extract were evaporated and disolved in 0.05 mL acetone (water free). Finally 1 µL of extract was analysed by GC/MS. The limit of detection was 0.06 mg/L serum. Calibration curves were linear over a range of 0.5-8.0 mg/L. The average recovery of DMP from human serum was 60 %. No changes in DMP concentration were observed in spiked human serum up to 5 days at 4°C.

In a case of acute phosphamidon intoxication, 3.5 mg DMP /L blood and 33.5 mg DMP /L urine were detected with the described method. This method provides excellent tool in the determination of the water soluble metabolites of organophsphate insecticides in the field of forensic as well as clinical toxicology.

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