An analytical method for the rapid screening of organophosphate pesticides in human biological samples and foodstuffs

Abstract Gas chromatography with nitrogen/phosphorus sensitive detection (GC/PND) and electron impact mass spectrometry (GC/MS) with selected ion monitoring provides a simple, rapid and sensitive method for the determination of organophosphate pesticides (OPs). A selective single-step extraction of 23 different OPs in urine, blood, serum and food samples (baby food, soft drinks and instant soups suspected of contamination from a blackmailing scare) is described. The OPs were extracted with 1 ml toluene (with and without addition of mevinphos as internal standard), using a 0.7 ml aliquot of urine, blood or serum sample. Food samples (0.2 g) were homogenised with water (0.5 ml) before extraction. An amount of 1 μl of the toluene phase (extraction supernatant) was analysed directly by GC/PND and GC/MS. The method was validated using spiked human serum. The OPs were mixed with serum containing 10 mg/ml disodium ethane diamine tetraacetic acid disodium salt (EDTA disodium salt) and stored up to 10 days at 4 and −20°C, respectively. The recovery rates of OPs in freshly spiked human plasma ranged between 50% (dimethoate) and 133% (dialifos). OPs in plasma proved to be stable at −20°C. Their levels decreased only slightly after storage at 4°C.