| Methods were developed for the residue analysis of chlorpyrifos and its toxic metabolite 3,5,6-trichloro-2-pyridinol (TCP) in water, soil and apple, and studied the effects of nitrogenous and phosphorous fertilizer s on dissipation of chlorpyrifos in soil. The main items as following:1. Detection conditionThe methods based on using high-performance liquid chromatography (HPLC) with reversed-phase C18 column, and gradient UV detection. The column was maintained at 25℃with a mobile phase flow rate of 1.0 ml·min-1. The mobile phase consisted of methanol-water (90:10, v/v) or acetonitrile-water (90:10, v/v). Chlorpyrifos and TCP were detected at 300 nm. The retention times of chlorpyrifos and TCP were 6.4 min and 3.6 min for the mobile phase of methanol-water (90:10, v/v), and 5.6 min and 2.5 min for acetonitrile-water (90:10, v/v). The detection limits for chlorpyrifos was found to be 0.5ng, and TCP was 0.15ng.The linearity was checked in the range between 0.50ng and 2500ng injected. The regression coefficients of the UV detector were from 0.9997 to 0.9999 for chlorpyrifos and TCP.2. Determination of chlorpyrofos and TCP residues in waterDifferent conditions of mobile phase, different kinds of extraction solvents and different amount of extraction solvents were studied. Ethyl acetate, dichloromethane, chloroform and petroleum ether were tried as the extraction solvent respectively, and the best extraction was obtained when using ethyl acetate. Water samples were extracted by liquid-liquid distribution, 50 mL ethyl acetate was used in the first partitioning step, and 30 mL was used in the second step.When adding of chlorpyrifos and TCP at the concentration of 0.01～5 mg·L-1, the average recoveries of chlorpyrifos and TCP were about 91.4%～105.1% and 90.6%～105.4%, and the relative standard deviation ranged from 0.99%～4.12% to 0.29%～9.33%. The lowest detectable concentration of chlorpyrifos and TCP in water sample were 2 ng·mL-1 and 0.6 ng·mL-1. The results showed that the method met the demand of pesticide residue analysis.3. Determination of chlorpyrofos and TCP residues in soilIn this study, an acetone: phosphoric acid (99:0.5 v/v) mixture was used as the extraction solvent. The purification step involved liquid–liquid distribution for which ethyl acetate was used as the extraction solvent. These results suggest that extraction by shaking and ultrasound-microwave extraction are suitable for the analysis of chlorpyrifos and TCP residue in soil.The average extraction recoveries of chlorpyrifos and TCP with concentrations of 0.1, 1, and 5 mg kg-1 from agricultural soil were determined. Four replicates of spiked soil samples were analyzed for each concentration. When extracting the residues by shaking, the average recovery of chlorpyrifos and TCP from the soil samples was found to be 94.8%～102.3% and 97.7%～99.8%, respectively, and the relative standard deviation was 3.4%～13.8% and 1.6%～14.5%, respectively. For ultrasound-microwave extraction, the average recovery of chlorpyrifos and TCP was 94.4%～100.0% and 94.9%～107.6%, respectively, and the relative standard deviation ranged from 5.7%～8.6% and 1.7%～ 8.5%, respectively.4. Determination of chlorpyrofos and TCP residues in soilAcetone alone was used as the extraction solvent, the efficiencies of extraction by shaking and ultrasound-microwave extraction were compared during the analysis of chlorpyrifos and TCP residue in soil and apple samples. The results indicated that both the methods were reliable and repeatable for the extraction of chlorpyrifos and TCP from soil and apples.The average extraction recoveries of chlorpyrifos and TCP with concentrations of 0.1, 1, and 5 mg kg–1 from the apple samples were determined. Spiked apple samples were fortified in four replicates. For extraction by shaking, the average recoveries of chlorpyrifos and TCP from the apple samples were 90.7%～95.2% and 93.4%～99.5%, respectively, and the relative standard deviation was 1.8%～15.1% and 2.1%～3.8%, respectively. For ultrasound-microwave extraction, the average recoveries of chlorpyrifos and TCP were 90.2%～98.0% and 92.3%～97.8% respectively, and the relative standard deviation was 2.9%～8.5% to 2.7%～6.0%, respectively. These results indicate that extraction by shaking and ultrasound-microwave extraction are suitable for the analysis of chlorpyrifos and TCP residue in apple samples.5. Effects of nitrogenous and phosphorous fertilizers on dissipation of chlorpyrofos residues in SoilThe effects of nitrogenous and phosphorous fertilizers on dissipation of chlorpyrifos in soils, spiked with chlorpyrifos were investigated under controlled laboratory conditions. The results showed that nitrogenous fertilizer can speed up the dissipation of chlorpyrifos, otherwise phosphorous fertilizer can slow down the dissipation of chlorpyrifos in soils. The order of chlorpyrifos dissipation followed N+P>N >CK>P within the soil. The half lives of chlorpyrifos were 9.7 d, 9.9 d, 11 d and 12 d in N+P, N, CK and P, respectively. The dissipation of chlorpyrifos related to the environment. The nitrogenous fertilizer could enhance dissipation of atrazine in soil, thus helpful to remediate the soil pollution of chlorpyrifos.
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