Simultaneous Determination of Pyrethroid, Organophosphate and Carbamate Metabolites in Human Urine by Gas Chromatography-Mass Spectrometry (GCMS)

We have developed a rapid, sensitive, and reliable method for simultaneous determination of the urinary metabolites of common insecticides in a single analytical run using gas chromatography-mass spectrometry (GCMS). Thirteen metabolites, one originating from carbamate, six from organophosphates, and seven from pyrethroids, were selected for method validation. Samples at different concentrations (0.5-15 mu g/L) were prepared by mixing working solutions containing the analytes with blank urine. After acid hydrolysis for 45 min at 90 degrees C, samples were processed with liquid-liquid extraction and derivatization by N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide (MTBSTFA) before analysis on GCMS. The limits of detection for all thirteen analytes were below 0.1 mu g/L. The recovery rates, evaluated at two concentrations (1, 10 mu g/L), were found to be 90.48%, on average. The precision of multiple analyses at three different concentrations (0.5, 5, 15 mu g/L) within one day or between 10 days was evaluated, and the resultant relative standard deviations were 8.1% or under. We also applied this method to analyze genuine urine samples collected from 30 human subjects, and successfully detected all the metabolites, with detection frequencies more than 50% for pyrethroid metabolites. In summary, this method is not only as good as others in performance, but is advantageous in terms of cost effectiveness and multiplicity of analytes.