Trace level determinations of carbamate pesticides in surface water by gas chromatography–mass spectrometry after derivatization with 9-xanthydrol

A sensitive and selective gas chromatographic mass spectrometric method, based on derivatization with 9-xanthydrol, has been established for the simultaneous determination of five carbamate pesticides (carbaryl, carbofuran, metolcarb, isoprocarb and ethiofencarb) in surface water. 4-Bromo-3,5-dimethylphenyl-N-methylcarbamate was chosen as the internal standard for analyzing water samples. The derivatization of carbamates was performed directly in water and the reaction conditions (9-xanthydrol of 50.0 mM, HCl concentration of 0.05 M, reaction for 60 min at 60 °C) were established through the optimization of various parameters. Under the established conditions, the limits of quantification were in the range of 0.007–0.028 μg/L, and the intra- and inter-day relative standard deviation were each less than 15% at concentrations of 0.1, 1.0 and 10 μg/L. None of the carbamate pesticides were detected in any of the sixteen surface waters analyzed.