A single-step procedure for the extraction and derivatization of carboxylic pesticides from aqueous samples is described. The acidic compounds, including phenoxy herbicides, were extracted from aqueous samples using tetrahexylammonium hydrogensulphate as a catalyst and were subsequently derivatized with pentafluorobenzyl bromide to volatile stable and electron-capturing derivatives. Analysis was performed by gas chromatography with electron-capture detection combined with negative-ion chemical ionization mass spectrometry. The recovery of the compounds was 108 ± 8%. Detection limits were typically 0.05 μg/1, using mass unit resolution. Highly contaminated samples required increased resolution (1000 ≤ Rf≤ 4000) for reduced chemical background and enhanced selectivity for detection at low-ppb levels. The method was applied to the determination of some phenoxycarboxylic pesticides in surface water and in blood samples. © 1993.
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