Kinetic–spectrophotometric determination of diquat based on a charge-transfer complex with cysteine

Abstract

The reaction involving the formation of a charge-transfer complex between diquat and cysteine was studied. The initial rate of the reaction, measured as a change in absorbance at 495 nm during 60 s, was linearly related to diquat concentrations from 0.5 to 28.0 µg cm^–3. The applicability of the method was demonstrated by the determination of diquat in commercial herbicides, waters, soils and potatoes.