Improved derivatisation method for the gas-liquid chromatographic determination of the herbicide oryzalin

Abstract

A rapid derivatisation method is described for the determination of the herbicide oryzalin. It involves the use of dimethylsulphinyl anion and methyl iodide or ethyl iodide. Gas-liquid chromatography is used with either an N-P or an electron-capture detector. The method was applied to the residue analysis of fortified sweet potatoes, soils and water. With an electron capture detector, residues as low as 0.01 µg g^–1 in sweet potatoes and soils and 0.001 µg g^–1 in water may be detected. For an N-P detector the limits of detection are 0.05 µg g^–1 in sweet potatoes or soils and 0.005 µg g^–1 in water. Recoveries ranged from 80–90% from these matrices at fortification levels of 0.08–0.5 µg g^–1. The choice of using either the methyl or the ethyl derivative is an added advantage.