Residue dissipation, evaluation of processing factor and safety assessment of hexythiazox and bifenazate residues during drying of grape to raisin

An analytical method for the simultaneous analysis of hexythiazox and bifenazate residues in grape and raisin was validated by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. The extraction method involved liquid-liquid extraction with ethyl acetate and dSPE cleanup with primary secondary amine (PSA). The drying of grape to raisin may increase or decrease residues of pesticides. During the raisin making process, the dissipation of residue was evaluated and the processing factor (PF) was established for drying. Dissipation data were best fitted to 1(st)+ 1(st)-order kinetics with a half-life ranging between 6-10 days for hexythiazox and 5-6 days for bifenazate. The PF value for overall raisin making was found to be 0.20-0.36 for hexythiazox and 0.14-0.15 for bifenazate indicating degradation of the residues. However, the PF value varies between 1.13-1.64 for hexythiazox and 0.94-1.12 for bifenazate during the drying process indicating concentration of the residues in drying. The dietary exposure on each sampling day was less than the respective maximum permissible intake (MPI). The residues in market samples of raisins were devoid of any risk of acute toxicity related to dietary exposure. The PF value generated will be useful for the field level management of residues in grape intended for raisin preparation.