Dissipation Kinetics of Trifloxystrobin -Tebuconazole mixture in Brinjal and Cowpea and their Risk Assessment

A method for estimation of residues of tebuconazole, trifloxystrobin and its metabolite in brinjal and cowpea was validated using liquid chromatography–tandem mass spectrometry with coefficient of determination (R²) ≧ 0.99. The untreated samples fortified with tebuconazole and trifloxystrobin, its metabolite in three levels 0.05–0.25 and 0.5 μg g⁻¹, showed an acceptable recovery in the range of 72 to 118 per cent with relative standard deviation, RSD ≦ 14.25. Nativo 75 WG, was applied thrice at the normal and double dosages at 7 d interval in brinjal from fruit setting, and applied at 7 d interval starting from pod formation stage in cowpea. Half-life of total trifloxystrobin at lower and higher doses was 0.44 and 1.02 d on brinjal, 0.85 and 1.22 d on cowpea, respectively. The half-life of tebuconazole on brinjal was 1.38 and 1.17 d, whereas in cowpea, the corresponding values were 0.99 and 1.61 d. The calculated waiting periods were 1.57 and 3.39 d for total trifloxystrobin and 5.15 and 4.90 d for tebuconazole in brinjal; while in cowpea the values were 3.01 and 6.09 d (total trifloxystrobin) and 3.96 and 6.88 d (tebuconazole). The risk assessment of the residues revealed that the combination product applied at lower and higher doses in brinjal and cowpea did not pose any risk to humans, even on the same d of application and hence can be safely recommended for management of pest complex in brinjal and cowpea under Indian conditions.