Simultaneous kinetic determination of zineb and maneb by the continuous addition of reagent technique

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Abstract
The continuous addition of reagent technique was applied to the simultaneous kinetic determination of zinc ethylenebis(dithiocarbamate)(zineb) and manganese ethylenebis(dithiocarbamate)(maneb) in mixtures. The method developed for this purpose is based on the continuous addition of zincon to a solution containing zinc(II) and manganese(II) released in the acid decomposition of the pesticides. The sequential formation of the zinc and manganese complexes with the reagent is monitored spectrophotometrically. Two consecutive kinetic curves are obtained, the slope of the straight portion of which is related to the concentration of each pesticide. The method allows the resolution of zineb-maneb mixtures at the µg ml–1 level over the ratio range 1:12–10:1, with an average relative standard deviation of 1.3%, and was applied satisfactorily to the determination of both pesticides in commercial formulations.