Analysis of organophosphorus pesticides in whole milk by solid phase microextraction gas chromatography method

Solid phase microextraction (SPME) was used for the extraction of residual coumaphos and dichlorvos in whole milk. The residues were analyzed by capillary gas chromatography equipped with nitrogen phosphorus detector (GC-NPD). A manual SPME holder with a 100-mu m polyacrylate fiber was used. The optimized conditions for extraction by SPME method were: sample agitation, absorption temperature of 30 degrees C, absorption time of 40 min, desorption time of 10 min, and sample volume was 16.0 mL in the vial. Under these conditions, the calibration graphs were linear in the range of 0.17 mu gL(-1) to 1.75 mu gL(-1) for coumaphos and 0.69 mu gL(-1) to 6.90 mu gL(-1) for dichlorvos. Precision was good with RSD values of 13% for coumaphos and 14% for dichlorvos. The detection limits (LOD) were 0.060 mu gL(-1) for dichlorvos and 0.052 for coumaphos. The quantification limits (LOQ) were 0.086 mu gL(-1) for dichlorvos and 0.066 mu gL(-1) for coumaphos. The results obtained in this study suggest that SPME is a suitable technique for residual pesticide analysis of milk. The data demonstrate that particular OP pesticides used in dairy farming in the region of Minas Gerais were found to contaminate cow whole milk, and the residues are not removed by treating the milk by boiling.