Study On The Analysis Of Difenoconazole And Its Metabolite Residues In Tea

As tea is the national beverage,chemical control has been relied on for a long time as the main means of control to ensure the production quantity and quality of tea production,while difenoconazole is widely used as a highly effective broad-spectrum fungicide to control anthracnose in tea.However,the residues of difenoconazole as a chemical agent in tea may be harmful to the environment and human beings.Thus,in this paper,the residual dissipation of difenoconazole and its metabolite difenoconazole-alcohol during the growth,processing and brewing of tea was investigated on an ACQUITY HSS T3 column using methanol and 10mmol/L ammonium acetate aqueous solution as mobile phases.The linearity of difenoconazole and its metabolite difenoconazole-alcohol was satisfactory in the concentration range of 0.001-5.0 mg/L with correlation coefficients greater than 0.9902.The recoveries in different tea mechanisms ranged from 71.2 to 118.6% with the RSDs of2.8-15.9%.The limits of quantification for both difenoconazole and difenoconazole-alcohol were 0.001 mg/kg in fresh tea leaves,green tea and black tea,and 0.0002 mg/L in tea infusion.The half-life of difenoconazole in tea leaves was 1.77 d,The residues of the metabolite difenoconazole-alcohol increased 1 d after application and then gradually dissipated,with99% dissipation of both parent and metabolite at 14 d after application.The dissipation rate of difenoconazole was 4% after processing the tea leaves picked at 1 d,5 d,7 d and 10 d after application according to the dynamic sampling time into green tea,while the degradation rate of its metabolite was 19%,and the total processing factors(PFs)were 0.86-1.05 and0.78-0.85,respectively,in comparison with the degradation rate of difenoconazole after processing into black tea,which was 3%,the degradation rate of its metabolite was-15%,and the total PFs were 0.83-1.13 and 0.82-1.66,respectively.0.82-1.66,the residues of both difenoconazole and its metabolite were relatively stable during the processing of tea.The total leaching rates(LRs)of difenoconazole and its metabolite ranged from 8.4-17.9% and31.8-38.9% during brewing of black tea and 15.4-23.5% and 30.4-50.6% during brewing of green tea.The LRs of difenoconazole and its metabolite difenoconazole-alcohol in black tea infusion were higher than those in green tea infusion.the potential dietary intake risk of both difenoconazole and its metabolite in tea infusion was well below 1% and negligible for human health,however,the risk probability of difenoconazole in fruits and vegetables required for daily diet reached 158%,so the MRLs for difenoconazole in different agricultural products worth to be re-evaluated for consideration.