ANALYSIS OF 3,5,6-TRICHLOROPYRIDINOL IN HUMAN URINE USING NEGATIVE-ION CHEMICAL IONIZATION GAS-CHROMATOGRAPHY MASS-SPECTROMETRY

A sensitive gas chromatographic-negative-ion chemical ionization mass spectrometric (GC-NCI-MS) method was developed to measure levels of the chlorpyrifos metabolite 3,5,6-trichloropyridinol (3,5,6-TCP) in human urine. The metabolic 3,5,6-TCP was isolated from urine by acid hydrolysis of urine aliquots, followed by diethyl ether extraction. The residues of ether extraction were taken up in o-xylene and derivatized with N-(tert.-butyldimethylsilyl)-N-methyltrifluoroacetamide (overall five-fold concentration). The structural isomer 3,4,5-trichloropyridinol was used as an internal standard in this analysis. This method was found to be linear for the determination of 3,5,6-TCP over the range 0.8-792 ng/ml. The limit of detection for 3,5,6-TCP in human urine was estimated to be 0.5 ng/ml. Low levels of 3,5,6-TCP (1-18 ng/ml of urine) were identified in control human urine samples. Structural confirmation of the background 3,5,6-TCP was obtained via GC-NCIMS-MS analysis.