Residue Analysis Of Pesticide In Vegetable And Rice And Degradation Dynamics Of Chlopyrifos In Rice

Organophosphorus pesticides were applied intensively and more frequently detected in vegetables in China, including dichlorvos, acephate, omethoate, dimethoate, parathion-methyl, chlorpyrifos, parathion, isofenphos-methyl, profenofos, triazophos and phosalone. Imidacloprid and buprofezin were applied widely in the rice production. The above organophosphorus pesticides residues of vegetable from the nine cities in China were detected with Gas Chromatograph, which provided important reference for the relevant food safety departments to formulate policies. An analytical method for determination of chlorpyrifos and buprofezin in rice were established by Gas Chromatography while another analytical method for determination of imidacloprid in rice was established by High Performance Liquid Chromatography in order to provide technical guidance for the rice into the market in line with national standards. In this study, we through field experiment and residual analysis method in environment researched the degradation dynamic in rice plant, soil and paddy water and the final residues in rice, husk, rice plant and soil. These provide an important theoretical and scientific basis for the formulation of guidelines of the pesticide and product registration in the rice.1. This experiment detected400vegetable samples (solanums72portions, melons64portions, cabbages72portions, Chinese cabbages60portions, green leafy vegetables64portions, beans68portions) by the detection methods of agricultural industry NY/T761-2008.3types of organophosphorus pesticides were detected in the samples, which are as follow:omethoate, chlorpyrifos and triazophos. The over-limit pesticides were omethoate and chlorpyrifos, wherein the detected rate and over-limit rate of chlorpyrifos is the highest. The overall detected rate and overall over-limit rate of organophosphorus pesticides of samples were4.50%-1.00%.2. For the different kinds of vegetables, organophosphorus pesticides were not detected in cabbages and broccolis, and over-limit rate of green leafy vegetables (spinach and lettuce) was the highest, which was3.13%. The over-limit pesticides in green leafy vegetables were omethoate and chlorpyrifos, wherein the omethoate had been abandoned. For the different kinds of cities, organophosphorus pesticides were not detected in H, and over-limit rate in F was the highest.3. An analytical method for determination of imidacloprid and buprofezin in rice were established by High Performance Liquid Chromatography (HPLC) and Gas Chromatography (GC). The residue of imidacloprid and buprofezin in rice were extracted with common solvent of acetonitrile and cleanup with florisil and NH2SPE mini column and determined by reversed phase column HPLC equipped with Diode array detector (DAD) and GC equipped with Electron Capture Detector (ECD). The average recoveries of imidacloprid were89.2%-96.4%and the relative standard deviations were2.5%-8.5%. The average recoveries of buprofezin were86.6%-105.8%and the relative standard deviations were2.6%-5.5%. The limits of quantification were0.02mg/kg for two pesticides. The simplicity, accuracy, precision and repeatability of the method well satisfied the essential rules of pesticide residue determination.4. An analytical method for determination of chlorpyrifos in rice was established. The residue of chlorpyrifos in rice was extracted with the solvent of acetonitrile and cleanup with Sodium chloride salting purification and determined by GC equipped with Flame Photometric Detector (FPD). The average recoveries of chlorpyrifos were87.9%-103.9%and the relative standard deviations were2.6%-4.7%. The limit of quantification was0.02mg/kg. The sensitivity, accuracy and precision of the method well satisfied the essential rules of pesticide residue determination.5. An analytical method for determination of chlorpyrifos in husk, rice plant, and rice soil and paddy water were established. The residue of chlorpyrifos was extracted with the solvent of acetonitrile and cleanup with Sodium chloride salting purification and determined by GC equipped with Flame Photometric Detector (FPD). The average recoveries of chlorpyrifos were86.9%-105.1%and the relative standard deviations were2.1%-8.8%. The limit of quantification was0.02mg/kg. The sensitivity, accuracy and precision of the method well satisfied the essential rules of pesticide residue determination.6. Degradation dynamic of480g/L chlorpyrifos micro-emulsion in rice plant, rice soil and paddy water were studied. The results showed that:the degradation dynamic of chlorpyrifos accorded with the kinetic equation:c=coe-kt. The half life of chlorpyrifos was5.6-6.5d in rice plant,10.5-14.8d in rice soil, and8.9-13.0d in paddy water. The results showed that chlorpyrifos was degraded easily in plant, soil and water.7. Terminal residues of480g/L chlorpyrifos micro-emulsion in rice, husk, plant and soil were studied. The results showed that:When the rice was treated for once and twice, on the40th day after the last application, the final residue of chlorpyrifos in rice soil was0.200-3.767mg/kg,0.228-1.957mg/kg in husk,0.030-0.182mg/kg in rice. These showed that the final residue increased as the application dosage and application times increased, or as the harvest interval decreased.8. The safety evaluation of the chlorpyrifos results suggested that480g/L chlorpyrifos micro-emulsion be used for controlling the rice leaf roller at once at a dose of75-100g/mo (active ingredients:36-48g/mo) with a safe interval of40days from harvest. The results of the final residue assay indicated that it made sure the safety of the harvested rice consumption and the effectiveness of the use of pesticides, when the chlorpyrifos were used in the recommended application dosage, application times and the harvest interval.