DETERMINATION OF POLAR PESTICIDES BY PHASE-TRANSFER-CATALYZED DERIVATIZATION AND NEGATIVE-ION CHEMICAL-IONIZATION GAS-CHROMATOGRAPHY MASS-SPECTROMETRY

A single-step procedure for the extraction and derivatization of carbo xylic pesticides from aqueous samples is described. The acidic compoun ds, including phenoxy herbicides, were extracted from aqueous samples using tetrahexylammonium hydrogensulphate as a catalyst and were subse quently derivatized with pentafluorobenzyl bromide to volatile stable and electron-capturing derivatives. Analysis was performed by gas chro matography with electron-capture detection combined with negative-ion chemical ionization mass spectrometry. The recovery of the compounds w as 108 +/- 8%. Detection limits were typically 0.05 mug/l, using mass unit resolution. Highly contaminated samples required increased resolu tion (1000 less-than-or-equal-to R(f) less-than-or-equal-to 4000) for reduced chemical background and enhanced selectivity for detection at low-ppb levels. The method was applied to the determination of some ph enoxycarboxylic pesticides in surface water and in blood samples.