Mobility Of Seven Pesticides Including Pirimiphos-methyl During Cooking And Fermentation Of Rice

Rice is the most common food all over the world. White spirit and rice wine are both popular traditional drink in China, produced by rice, sorghum or wheat. Pesticides used on rice plant induce inevitable safety problems in wine-making industry. Risk of pesticide residues is an important scientific problem. This study established a multi-residue detection method for the commonly used pesticides in rice, white spirit and rice wine using gas chromatography with mass spectrometry detector, evaluated matrix effects and the stability of selected pesticides in different matrix extracts, and studied on the degradation of pesticides in cooking and fermentation process of rice.Residue analysis and dynamics studies of cyhalofop-Butyl, carfentrazone-ethyl, bispyribac-sodium and MCPA-Na in Rice, Soil and Paddy Water were performed. The active metabolite of cyhalofop-Butyl was studied as well. Residue analysis methods of cyhalofop-Butyl, carfentrazone-ethyl, bispyribac-sodium and MCPA-Na in rice plant, brown rice, rice hull, soil and paddy water were established. The field trials were carried out in Beijing, Hunan and Jiangsu. The pesticides were applicated at the end of tillering period of rice plant. According to the results of terminal residue trials, the terminal residues of cyhalofop-Butyl, carfentrazone-ethyl, bispyribac-sodium and MCPA-Na in rice plants, soil, brown rice, rice hulls were lower than the detection limits and the existing MRLs at the harvest time. In consideration of these results, the pesticides in the work were mostly chosen from insecticide, fungicide and fumigant.This study investigated two pre-treatment methods, solid-phase extraction (SPE) and QuEChERS. The recoveries for both methods of the pesticides in rice, white spirit and rice wine are60-120%, and good linearities between0.05mg/L and2mg/L are shown, with the correlation coefficients greater than99%. The QuEChERS method is easier and cheaper, compared with the solid-phase extraction method. So we choose the QuEChERS method. The recoveries of the method are between67-113.5%, with the limit of detection of3-20μg/L and the limit of quantification of10-50μg/L. Pirimiphos-methyl, acetochlor, chlorpyrifos, butachlor, tebuconazole, cypermethrin and azoxystrobin were the seven pesticides recycled by the QuEChERS method.Baesd on this method, the work studied on matrix effects of7pesticides including pirimiphos-methyl in rice, white spirit and rice wine using gas chromatography mass spectrometry detection. The results showed that the7pesticides had matrix enhancement effect in rice matrix, especially acetochlor, butachlor and beta-cypermethrin. The7pesticides had matrix-weakening effect in white spirit and rice wine matrix, especially pirimiphos-methyl, chlorpyrifos and beta-cypermethrin. The lower the concentration is, the more obvious the matrix effect is. We used corresponding matrix standard solutions to reduce the matrix effects. The stability of7pesticides in different matrix extracts under different storage conditions was evaluated. It was found that the stability of pesticides in solution is related with the pesticides’physicochemical property. The unstable pesticides should be analyzed as soon as possible. The stability of solutions is relevant with both the solvent evaporation and the decomposition of compounds.The study investigated the degradation of7pesticides including pirimiphos-methyl in the steeping, washing and steaming process of rice. According to the results, the steeping and washing process showed higher removal rate for the water-soluble pesticides. The removal rates of double washing process and steeping-washing process were in similar level, which showed advantage over washing process. The steaming process showed the highest removal rate as67.4%-95.7%. Then the degradation of7pesticides in the white spirit fermentation process was studied. The fermentation process included raw material fermentation and ripe material fermentation. In the raw material fermentation process, the results showed that the7pesticides were all below1mg/L on the5mg/kg addition level to rice four days after fermentation. The detective concentration decreased with time. The fermentation is in a strong period after3days. The pesticides concentration all decreased after distillation. In the ripe material fermentation process, the pesticides concentrations were obviously less than in the raw material fermentation process at the forth day of fermentation. Acetochlor, butachlor and pirimiphos-methyl could not be detected after seven days.The pesticide concentration decreased with time. Only trace chlorpyrifos and azoxystrobin could be detected after distillation.The degradation of7pesticides in the rice wine fermentation process were studied. Butachlor could not be detected after three days. Tebuconazole and acetochlor could not be detected after seven days. The pesticides concentration all decreased with time. Only trace chlorpyrifos, beta-cypermethrin, pirimiphos-methyl and azoxystrobin could be detected after fermentation. There were no pesticide residues in rice wine after boiled.This work studied on the degradation of7pesticides in the white spirit and rice wine fermentation process. The study applies important scientific basis for the establishment of China’s pesticide residues in wine-related laws and regulations in the future.