Dissipation kinetics and evaluation of processing factor for fluopyram + tebuconazole residues in/on grape and during raisin preparation

A field dissipation study was conducted in grapes and during raisin preparation to evaluate the pre-harvest interval (PHI) and processing factor (PF) for the residues of fluopyram and tebuconazole. An analytical method was established for the simultaneous extraction and analysis of fluopyram, fluopyram benzamide, and tebuconazole in grapes and raisins by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The method provided a limit of quantification (LOQ) of 0.005 and 0.01 mg kg− 1 and a recovery of 80.35%− 92.21% and 79.25%− 91.27% in grapes and raisins, respectively. The residues dissipated following 1st+ 1st-order kinetics with a half-life of 7.5–13.5 days for fluopyram and 6.0–9.5 days for tebuconazole. A PHI of 50 days is proposed for fluopyram + tebuconazole (400 suspension concentrate (SC)) formulation in grapes. The dissipation during raisin preparation also followed nonlinear 1st+ 1st-order kinetics with a half-life of 4.0–6.0 days for fluopyram and 2.5–5.0 days for tebuconazole. Direct washing and oil dipping of fresh grapes removed 71.43–72.72% of tebuconazole residues and 53.12–60.43% fluopyram residues. The PF values calculated at various stages of raisin preparation were < 1, indicating the degradation of residues during raisin preparation. The residues in market samples of grapes and raisins were well below their respective maximum residue limits (MRLs). The dietary exposure calculated based on average daily consumption was less than the respective acceptable daily intake (ADI), indicating no risk through dietary exposure. The PHI and PF values established will ensure the field level management of fluopyram and tebuconazole residues in grapes and raisins.