Dissipation kinetics, safety evaluation and decontamination of residues of the combi-formulation emamectin benzoate 1.50% + fipronil 3.50% SC in/on chilli.

Abstract

A field experiment was conducted to evaluate the persistence of emamectin benzoate 1.50% + fipronil 3.50% SC at recommended and 1.25 times the recommended doses on green, red chilli fruits and soil. QuEChERS method was validated for reliable and effective analysis of residues in green, red chilli fruits and soil matrices. Limit of quantification (LOQ) for emamectin benzoate and fipronil on chilli was 0.01 mg kg^-1 and 0.002 mg kg^-1, respectively. Initial deposits of emamectin benzoate and fipronil on green chilli at X dose were 0.261 and 0.321 mg kg^-1, respectively and at 1.25X dose residues were 0.319 and 0.394 mg kg^-1, respectively. Whereas, initial deposits of emamectin benzoate and fipronil on chilli cropped soil at X dose were 0.015 and 0.143 mg kg^-1, respectively and at 1.25 X dose were 0.260 and 0.171 mg kg^-1, respectively. In red chilli fruits, the residues of both the test insecticides were found < LOQ at final harvest at both the doses. Safe waiting periods of 5.26 and 9.06 days for emamectin benzoate and fipronil as combi-product was suggested at X and 1.25 X dose, respectively. The half-lives for test combi-product ranged between 1.26 and 1.71 days. Dietary risk assessment revealed that Theoretical Maximum Daily Intake (TMDI) was < Maximum Permissible Intake (MPI), while Hazard Quotient (HQ) was < 1, thus indicating the combi-product to be safe for consumption. Treating chilli fruits with lukewarm water + 5% NaHCO₃ solution for 10 min removed maximum residues (63.82%) and proved as a good house hold practice.