ANALYSIS OF SULFONYLUREA HERBICIDES BY GAS-LIQUID-CHROMATOGRAPHY .3. MASS-SPECTROMETRY AND MULTIRESIDUE DETERMINATION

A method is described for the determination of sulfonylurea herbicides by gas chromatography (GC). Chlorimuron-ethyl, cinosulfuron, primisulfuron-methyl, thifensulfuron-methyl, triasulfuron and tribenuron-methyl were converted into thermostable derivatives by reaction with diazomethane in ethyl acetate. The resulting N,N'-dimethyl derivatives were suitable for analysis by GC. Two of the herbicides formed multiple derivatives. The identity of the derivatives was confirmed using chemical ionization and electron impact mass spectrometry and nuclear magnetic resonance. The proposed structures of the ions in the electron impact mass spectra were confirmed using high-resolution, metastable ion decomposition and deuterium-labelling techniques. The derivatization was incorporated into multimethods for the residue analysis of the six sulfonylurea herbicides in water, soil and wheat samples. Recoveries ranged from 88% to 122% in water (0.1 mug l-1), 53% to 99% in soil (1 mug kg-1) and 41% to 120% in wheat (0.2 m kg-1).