Vol. 4, Issue 1 (2020)
A differential pulse polarographic method for the determination of benomyl has been developed and which has been validated for soil adsorption study of this fungicide on four Indian soils of different characteristics. The method is based on the microwave assisted alkaline hydrolysis of the fungicide with sodium bicarbonate to carbendazim and n-butylamine, the letter upon reaction with carbon disulphide form n-butyldithiocarbamate which upon reaction with copper (II) perchlorate results into copper (III) dithiocarbamate complex which exhibit an analytical useful diffusion controlled peak at -94 mV (vs. SCE). Benomyl has been determined in the linearity range 1.45-14.56 μg mL-1. The adsorption studies of this fungicide on four soils has been explained by using Freundlich’s adsorption equation and the adsorption isotherms obtained are of L-type of Gile’s classification. The high values of Kf, Kd and Koc indicate that benomyl is strongly adsorbed on to soils which inhibits its penetration into water bodies. This is further substantiated by the Groundwater Ubiquity Score (GUS) which is in the range 0.30-0.37, classifying it as a non-leacher pesticide.
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