Digestion, Residual Analysis And Risk Assessment Of 40% Thiophanate-methyl·Penconazole Suspension On Apples

In this dissertation,a simple and sensitive method was developed to determine the thiophanate-methyl and its metabolites carbendazim,penconazole in apple and soil by liquid chromatography-tandem mass spectrometry（LC-MS/MS）.Under the optimized conditions,the apple and soil samples were vortexed with acetonitrile and methanol,respectively.Then,the extracts were purified by PSA,and detected on an Agilent XDB-C₁₈ column using a methanol-0.2%formic acid/water solution as the mobile phase.The results showed that under the optimized conditions,the matrix-matched standard curves of thiophanate-methyl,carbendazim,and penconazole had a good linearities in the range of 0.005⁰.5μg/mL,with the correlation coefficients（R²）were all>0.999.The limit of detection（LOD）and limit of quantitation（LOQ）of the target compound was 0.006 and 0.02 mg/kg,respectively.The result showed that the response of thiophanate-methyl,carbendazim and penconazole were suppressed in apple and soil samples.In this study,the use of matrix-matched external calibration was recommended to modify the effect of the matrix on quantification.The average recoveries of thiophanate-methyl,carbendazim and penconazole in apple and soil samples were 74.38%¹00.43%,75.53%¹09.17%,77.02¹02.31%and70.45%⁹2.84%,76.32%⁹8.03%,78.09%¹03.81%,respectively,with the relative standard deviations（RSDs）were<10%.The field trails were conducted in Guizhou,Tianjin,Shandong province during the agricultural season in 2016 and 2017 to determine the dissipation dynamics and final residues of thiophanate-methyl,carbendazim and penconazole in apple and soil samples.The results showed that the half-life of thiophanate-methyl in apple and soil samples were 6.79 d and 2.21 d,and penconazole in apple and soil samples were7.07⁷.97 d and 4.99⁸.25 d,respectively.The final residues of thiophanate-methyl in apple and soil samples were<0.02⁰.82 mg/kg and<0.02⁰.21 mg/kg,respectively.The final residues of penconazole in apple and soil samples were<0.02⁰.39 mg/kg and<0.02¹.11 mg/kg,respectively.Following the recommended application method,the dietary intake risk quotient（RQc）and acute intake risk quotient（RQa）of thiophanate-methyl and penconazole in apple were far below 1,indicated that the risk of thiophanate-methyl and pentothiazan were acceptable to Chinese.