Optimization Of Determination Method And The Comparison Of Contaminant Levels Of OPPs In Animal Products

Organophosphorus pesticides (OPPs) are one of the most common classes involved in poisoning because of the inhibition of acetyl-cholinesterase. Even if OPPs are less persistent in the environment than organochlorine pesticides, they can also reach the food chain and may therefore represent risk to human health. So these substances accumulated in the animal products have got more and more attention. Therefore, it is of great significance that to establish the multi-residue determination method for OPPs and their metabolites.A method for the quantitative determination of58OPPs residues (including metabolites) in aquatic products, meat products, egg products and milk products of China Total Diet Study (TDS) by dual gas chromatography-dual pulse flame photometric detection and gas chromatograph-mass spectrometry (GC-MS) was developed. Because of the complex matrix and high fat content of the animal original foods of TDS, a two-step clean-up procedure was used during the sample pretreatment. The animal original samples were extracted by acetone and dichloromethane, and followed by gel permeation chromatography (GPC) and the Carb-NH2SPE clean-up.Using the external standard method for quantitative, the response of each OPP showed a good linearity with its concentration by GC-PFPD detection, the linearity correlation was not less than0.99. The limits of detection (LOD) of the OPPs were in the range of0.0003-0.250mg kg-1and the limits of quantitation (LOQ) were in the range of0.001～0.833mg kg-1. The recoveries performed by blank samples spiked at low, medium, and high fortification levels were in the range of50.4%～129.5%with relative standard deviations (RSD, n=6) of1.0%～31.8%. The results of method validation of GC-MS was also satisfactory with LODs in the range of0.0001～0.326mg kg-1LOQs in the range of0.001-1.087mg kg-1and the recoveries at low, medium, and high fortification levels were in the range of51.5%～129.8%and with RSD (n=6) in the range of0.9%～ 31.2%. The two methods with quatification by GC-PFPD and confirmation by GC-MS were successfully applied to the determination of OPPs in animal original samples (including aquatic products, meat products, egg products and milk products) of TDS.The contamination levels of58OPPs residues in4kinds of animal samples of TDS in2007and2009(including96samples in total in12provinces, cities or autonomous regions) were relatively low. Excluding theegg products and the milk products of2009TDS, the other six groups of TDS were all detected with OPPs residues. The aquatic products and meat products were frequently detected with OPPs at low levels, which posses more than half of the positive samples. The positive results were all lower than the MRL of CAC, excluding acephate residues (65.18μg/kg) in meat products of Guangxi of2007TDS. The detection rate of animal products of2007TDS was37.5%with residues in the range of0.92-65.18μg kg-1,and the detection rate of animal products for2009TDS of was10.4%with a contamination range of1.0-43.32μg kg-1.DDVP was frequently detected in aquatic products, egg products and milk products of2007TDS. Compared to2007TDS, the detection rates of OPPs in animal products of2009TDS were lower. However, the detection of monocrotophos in animal products of2009TDS suggested that the illegal use of high toxic OPPs still exist in some regions of China. So it is a long-term task to strengthen the management of OPPs use and to improve the ability of monitoring the residue of OPPsin food iterms to ensurehuman health.