Analysis of 3,5,6-trichloropyridinol in blood plasma

Hydrolysis of chlorpyrifos in natural waters of the Chesapeake Bay

Chlorpyrifos is the most widely used insecticide in the Chesapeake Bay region. Recent studies show that this organophospate chemical is consistently present in the air, rain and surface waters of the Chesapeake Bay region, suggesting a long environmental half-life. Hydrolytic degradation of chlorpyrifos is likely a dominant removal process, but existing hydrolysis data do not reflect conditions in the Chesapeake Bay. In this project, hydrolysis rates of chlorpyrifos were measured in sterilized, ambient water from the mouth of four Chesapeake Bay tributaries ranging in salinity from 0 to 17 ppt. The measured hydrolysis half-lives varied from 24 d in the Patuxent River to 126 d in the Susquehanna River. These results indicate that pH alone cannot be used as a single parameter to predict hydrolysis under field conditions. The influence of copper concentration, and other water constituents, need to be further evaluated as they may emerge as independent predictors to assess the fate of pesticides in natural systems.

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.