The authors developed a sensitive analytical method for the determination of dialkyl phosphates (DAPs) in meconium. This method was applied to determine the DAPs, which are non-specific metabolites of the organophosphate pesticides (OPs), in meconium of newborns by mothers who live in rural areas in Crete, Greece. DAPs are considered as biomarkers of exposure to OPs. Meconium is produced in the foetus at approximately 16 weeks of gestation and it acts as a repository of many xenobiotics. The determined organophosphate metabolites were dimethylphosphate (DMP), diethylphosphate (DEP), dimethylthiophosphate (DMTP), diethylthiophosphate (DETP), and diethyldithiophosphate (DEDTP). The DAPs were extracted from meconium by liquid-solid extraction, derivatized, and analysed by gas chromatography-mass spectrometry (GC-MS). The mean percentile recoveries were 76.9%, 65.2%, 94.1%, 109.4%, and 107.2% for DMP, DEP, DMTP, DETP, and DEDTP, respectively. The percentage of positive samples was 92.1% for DMP, 36.8% for DEP, 60.5% for DMTP, 63.2% for DETP, and 57.9% for DEDTP. Mean (+/- standard deviation) and the range concentrations of the positive samples (ng g(-1)) were 126.74 +/- 142.73 (10.64-739.45), 11.46 +/- 20.43 (1.50-79.14), 215.05 +/- 187.34 (8.54-662.16), 4.92 +/- 5.09 (1.25-19.04), and 1.84 +/- 2.07 (0.5-8.04) for DMP, DEP, DMTP, DETP, and DEDTP, respectively. Statistical analysis revealed no significant difference in meconium levels between high- and low-risk groups of exposure of pregnant women. However, the results of this study demonstrate that DAPs in meconium may be considered as a potential biomarker for the assessment of foetal exposure to organophosphate pesticides.
