Residue dissipation and dietary risk assessment of penconazole, bupirimate and its metabolite ethirimol in grapes using UPLC-MS/mS

A 25% penconazole-bupirimate microemulsion was applied three times at 7-day intervals at a rate of 300 mL/ha (equivalent to 75 g a.i. ha−1) under field conditions. Residues of penconazole, bupirimate and its metabolite ethirimol in grapes were determined using ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) following QuEChERS extraction. Mean recoveries ranged from 92.4% to 95.3% for penconazole, 91.9% to 98.5% for bupirimate, and 89.1% to 90.5% for ethirimol, with relative standard deviations (RSDs) of 1.3-2.2%, 0.95-2.0% and 0.65-3.8%, respectively. The Limits of Quantification (LOQs) for all pesticides were 0.01 mg/kg, meeting the detection requirements. The half-lives of penconazole and bupirimate in grapes were 4.6-7.5 days and 3.5-6.7 days, respectively. The dissipation of ethirimol could not be described using first-order kinetics. At 14 d post-final spray, penconazole residues ranged from < 0.01 to 0.12 mg/kg, bupirimate from < 0.01 to 0.18 mg/kg, and ethirimol from 0.015 to 0.22 mg/kg. The chronic dietary risk assessment suggested that the long-term dietary intake risk of target pesticide residues was within the acceptable threshold under the assumptions adopted in this evaluation. Notably, the RQ value of ethirimol was relatively close to the critical limit, and no national MRL for ethirimol in grape has been established in China to date.