A Sequential Spectrophotometric Method for the Determination of Paraquat and Diquat in Plasma

Abstract

Abstract A sequential spectrophotometric method for the simultaneous determination of paraquat and diquat in plasma using second-derivative spectroscopy after ion-pair liquid-liquid extraction was developed. The paraquat and diquat in the last extract are reduced with alkaline sodium dithionite to coloured complexes whose absorption peaks appear at a different wavelength. The two herbicides can thus be determined sequentially over the wavelength ranges 454.3—446.4 nm (diquat) and 460—396 nm (paraquat), respectively.