Persistence and Efficacy of Culinary Processes in Removing the Residues of Chlorpyrifos and Ethion in Brinjal

A rapid multi-residue modified QuEChERS method has been validated to analyse ethion and chlorpyrifos residues in brinjal by GC-FPD. Method validation revealed correlation coefficients (r2) higher than 0.990 with the insecticides linearity ranging from 0.005 to 1.00 mg kg-1. The limit of quantification (LOQ) for chlorpyrifos was 0.01 mg kg-1 and ethion 0.05 mg kg-1. The persistence of chlorpyrifos and ethion on brinjal fruits was studied after their application on the brinjal crop @ 300 (standard dose) and 600 g a.i. ha-1 (double dose), and 500 (standard dose) and 1000 g a.i.ha-1 (double dose) respectively in the field. Initial deposits of chlorpyrifos on brinjal fruits were 1.092 and 1.982 mg kg-1 and those of ethion 0.911 and 1.731 mg kg-1 at the standard and double doses, respectively. The half life values of chlorpyrifos and ethion deposits were 1.55 and 2.15 d and 1.58 and 1.68 d at the two doses respectively. The respective waiting periods were 3.81 and 7.13 and 1 and 1.33 d respectively. Washing of the fruits with tap water, 2 per cent NaCl and lukewarm water was effective in removing residues to the tune of 36.17, 45.74 and 48.63 per cent for both chlorpyrifos and ethion, respectively. However, cooking (open pan and microwave) was found most effective (up to 70.06%) in removing insecticide residues.