DETERMINATION OF ACID HERBICIDES IN AQUEOUS SAMPLES BY LIQUID-SOLID DISK EXTRACTION AND CAPILLARY GAS-CHROMATOGRAPHY

A simplified procedure for extraction and analysis of chlorinated acid herbicides in aqueous matrices using modern filter disk extraction technology is presented. An acidified water sample is extracted with a 47-mm polystyrene-divinylbenzene filter disk and the analytes are eluted with a mixed methanol-methyl tert.-butyl ether solvent. After extract drying, the analytes are esterified with diazomethane and analyzed by gas chromatography with electron-capture detection. The discussion includes extraction disk selection, sample acidity and salting requirements, elution volume requirements and the effect of sample volume on recovery. Method detection limits are given as well as accuracy and precision data on four fortified matrice -reagent water, dechlorinated tap water, biologically active surface water and high humectant ground water.