Study On The Characterization Of Parathion And Its Metabolites In Rats

Parathion(O,O-diethyl-O-p-nitrophenyl thiophosphate), one of the toxic organophosphorus pesticides, is used in a number of agricultural activity in the pest control to make higher production. Parathion is mainly metabolized to p-nitrophenol, paraoxon, diethylthiophosphate (DETP) and diethylphosphate (DEP) in animal biodegradation. This toxic chemical can damage nerve system through the inhibition of acetylcholinesterase (AChE) activity. Exposure to parathion could cause central nervous system depression. The study on the metabolic mechanism of parathion is significant for the evaluation on its biological toxicity and environmental effect. Due to the low concentration of parathion and its metabolites in bio-samples, a sensitive, effective and reliable method is necessary for their detection.Gas chromatography-mass spectrometry (GC-MS) is a method that combines the features of gas chromatography and mass spectrometry to identify different substances. Capillary electrophoresis (CE) is an important technique in the area of liquid-phase separations. The analytes can be separated and then detected by the detector due to the different velocities. Microdialysis sampling is a new sampling method for the real-time, on-line, continuous determination of analytes in vivo.Recently, pesticide residue is an important environment issue which caused contamination to water, soil, air and animal. Identifying residual pesticide metabolites will provide valuable information for treatment decisions and have a positive effect on food safe and the environmental health of human.In this study, a selective and sensitive GC-MS and CE-ED method were developed for the qualitative and quantitative analysis of parathion and its metabolism in biological samples. We also laid our emphasis on the research of microdialysis technique for the sampling of biological samples. It was applied to analysis DEP, DETP, PNP, paraoxon, and parathion in rat serum, liver, kidney, spleen, striatum and hypothalamus and estimated the parathion metabolic mechanism after parathion administration.The primary research includes four chapters: Chapter1. IntroductionIn Chapter1, the development, principle and applications of gas chromatography-mass spectrometry, microdialysis and capillary electrophoresis were outlined. The characteristics of parathion and its metabolites were introduced, and the applications of GC-MS, MD, CE-ED in environmental analysis were highlighted, as well as the meanings of this paper.Chapter2. Simultaneous Determination of Parathion and Its Metabolites by GC-MSParathion (O, O’-diethyl-O-p-nitrophenyl phosphorothionate) is one of the commonly used organophosphorus pesticides for pest-control and agricultural activities. Four metabolites including p-nitrophenol, paraoxon, diethylthiophosphate (DETP) and diethylphosphate (DEP), have been identified during animal biodegradation. In this study, a highly specific and sensitive gas chromatography-mass spectrometry (GC-MS) method was optimized for the first time to analyze parathion and its four metabolites simultaneously qualitatively and quantitatively. These five analytes (i.e., parathion, p-nitrophenol, paraxon, DETP, and DEP) could be well separated and detected within30mins. The linear ranges were from6.25-500μg/L, with the correlation coefficient between0.996and0.999. The limits of detection for parathion were4.1μg/L and6.0μg/L for p-nitrophenol and4.1μg/L for paraoxon and16.7μg/L for DEP and2.0μg/L for DETP, respectively. Using the optimized GC-MS protocol, parathion and its metabolites were monitored in rat serum and tissues including liver, kidney, spleen after1mg/kg parathion administration. The concentration of parathion and its metabolites in rat serum and tissues varied over a wide range between0.0122and7.646mg/g.Chapter3. Determination of Parathion and its Metabolites by GC-MS with Microdialysis Technique on the Rats Brain and Serum after Exposure to ParathionIn the present study, we used an in vivo microdialysis sampling method coupled with GCMS analytical system to measure the parathion and its metabolites in rat brain and blood.The method has been applied to analyze parathion and its metabolites in rats’serum, striatum and hypothalamus to study the toxicity of parathion. The content of parathion and its metabolites in these tissues of rat was sampled in vivo continuously with microdialysis sampling system by implanting of microdialysis probe and detected by GC-MS method. The concentration of parathion was1.14×10-5mol/1in the serum of rats. It was proved to be sensitive and reproducible with wider linear range. These properties enabled its promising application in physiology and food security monitoring.Chapter4. Simultaneous Determination of Parathion and its Metabolites by Micellar Electrokinetic Capillary Chromatography-Electrochemical Detection with CMK-3Modified ElectrodeIn this paper, it is the first time that a mesoporous carbon material (CMK-3) modified carbon disk electrode was used in MECC-ED for the determination of parathion (PA) and its metabolites paraoxon (PO) and p-nitro phenol (PNP). The MECC separation parameter was investigated. The three compounds were separated within15min in0.03mol/L borate buffer (pH7.8, containing0.03mol/L SDS). Voltage of15kV was selected as the applied voltage. Compared with the unmodified electrode, CMK-3modified electrode produced higher sensitivity. The detection limits were as low as5.2×10-8mol/L for PNP (S/N=3),5.2×10-8mol/L for PO, and1.0×10-7mol/L for PA respectively. The method provides reliable basis to the further study on the organophosphorus pesticides residues in agricultural products.