| In this study,chlorfenapyr and difenoconazole were used as target compounds,a residue analysis method for two pesticides and their metabolites in different pepper matrices was established,and the field residue test and final residue test of pepper were carried out on the residue change law during the growth and processing of pepper,and the dietary risks of chlorfenapyr and difenoconazole were evaluated under the premise of considering the two metabolites.The main findings are as follows:1.Based on the optimized Qu ECh ERS pretreatment technology,the residual detection methods of chlorfenapyr and difenoconazole in four pepper matrices were established,showing a good linear relationship in the range of 0.005～2.0 mg/L,R2 was greater than 0.99,all four peppers had no matrix effect,the average recovery rate was 76%～105%,the RSD was 0.3%～10.7%,and the limit of detection（LOD）and limit of quantification（LOQ）were0.005 mg/kg.This method has a good linear range,and both accuracy and precision meet the requirements for pesticide residue analysis.2.The results of the degradation dynamics and final residue tests of chlorfenapyr and difenoconazole on peppers show that the digestion law of the two pesticides conformed to the kinetic equation,the half-life t1/2 was 2.81 d and 7.15 d,respectively,and the two pesticides were degraded to produce metabolites.The final residue levels of chlorfenapyr on the 14 and21 days after the last application were 0.351 and 0.354 mg/kg,with a median standard residue test（STMR）of 0.353 mg/kg and a highest residue value（HR）of 0.354 mg/kg.The final residues of difenoconazole at 7 and 10 days after the last application were 0.975 and 0.954mg/kg,with the median residue test（STMR）and highest residue value（HR）were 0.965mg/kg and 0.975 mg/kg,respectively.3.The different processing steps of chlorfenapyr and difenoconazole in the substrate of pickled pepper,chopped pepper and pepper paste and the residual degradation law of pepper fermentation were studied.The results showed that the total processing factor of chlorfenapyr and difenoconazole in the matrix of pickled pepper,chopped pepper and pepper paste was0.27～0.68,and the degradation rate was 32.0%～72.6%,and different processing steps had a certain effect on the residual changes of chlorfenapyr and difenoconazole residue.The degradation of difenoconazole in pickled pepper,chopped pepper and pepper paste matrix conformed to the first-order kinetic equation,and the half-life t1/2 were 23.90 d,36.48 d and26.88 d,respectively.The degradation law of chlorfenapyr in chopped pepper and pepper paste conformed to the first-order kinetic equation,and the half-life t1/2 was 20.39 d and 9.50d,while the residual chlorfenapyr retention in pickled pepper increased slowly.Chlorfenapyr and difenoconazole were degraded into metabolites in 3 pepper matrices.4.The dietary risks of chlorfenapyr and difenoconazole in peppers were evaluated.The results showed that the chronic dietary risk（%ADI）of chlorfenapyr and difenoconazole in fresh pepper,pickled pepper,chopped pepper and pepper paste was 0.53%～8.18%,the acute dietary risk was 0.10%～11.33%,and the risk of both diets was<100%,which was acceptable.It can be suggested that the MRL of chlorfenapyr on pepper is 1.0 mg/kg,the short-term intake is 0.0047 mg/kg·d b.w.,and the acute dietary risk<100%,which is 13.67%,which does not pose a threat to human health. |
