KINETIC DETERMINATION OF DICOUMAROL ON GRAIN BY USING STOPPED-FLOW MIXING METHODOLOGY

A simple and fast kinetic method for the direct determination of dicoumarol on grain was developed. It involves measuring the initial rate of the colour-forming reaction (lambda = 475 nm) undergone by Gibbs' reagent in a basic medium (pH 9.0) in the presence of dicoumarol. Stopped-flow mixing methodology was used to obtain kinetic curves. This allowed reagent manipulation to be minimized and the method to be automated to some extent. The calibration graph was linear over the range 3-20 mug ml-1. Other anticoagulant rodenticides such as bromadiolone, difacinone and warfarin are tolerated in 20-fold excess. The method was satisfactorily applied to the direct analysis of wheat and oat samples spiked with dicoumarol (mean recovery, 92.7%).