Identification of a major human urinary metabolite of metolachlor by LC-MS/MS

• Published in: Bulletin of environmental contamination and toxicology Vol. 58; no. 6; pp. 929 - 933
• Main Authors: DRISKELL, W. J, HILL, R. H
• Format: Journal Article
• Language: English
• Published: New York, NY Springer-Verlag 01.06.1997; Springer Nature B.V
• Subjects: Acetamides - metabolism; Acetamides - urine; Biological and medical sciences; chromatographie; chromatography; Chromatography, Liquid; cromatografia; espectrometria de masas; Herbicides - metabolism; Herbicides - urine; Humans; Mass Spectrometry; Medical sciences; Metabolites; metolachlor; metolachlore; metolacloro; Occupational Exposure; Pesticides, fertilizers and other agrochemicals toxicology; Pilot Projects; Reference Standards; spectrometrie de masse; Toxicology; United States; United States Environmental Protection Agency; United States; Human; Urine; Solid phase extraction; Biological fluid; Chemical analysis; Metabolite; Coupled method; Pesticides; HPLC chromatography; Agricultural industry; Biological marker; Occupational exposure; Herbicide; Biological monitoring; Mass spectrometry MS/MS; Carboxamide; Organic amide; Qualitative analysis; Occupational medicine
• ISSN: 0007-4861; 1432-0800
• DOI: 10.1007/s001289900423

Metolachlor is a preemergence herbicide commonly used on soybeans, corn, and other crops. Herbicides are the most used class of pesticides, and metolachlor is one of the top three herbicides, with 40-60 million pounds used annually. Recently, we have been involved in studies of herbicide exposure that required us to develop procedures to measure metolachlor metabolites, alachlor metabolites, and other pesticide metabolites in urine. When we began the study, we found that neither alachlor nor metolachlor metabolism in humans was well understood although alachlor metabolism had been studied in monkeys. Therefore, to understand the metabolism of alachlor in humans, we analyzed for alachlor metabolites in the urine of occupationally exposed subjects. We were able to identify a major human metabolite of alachlor, alachlor mercapturate. Metolachlor metabolism has not been studied in humans, and only a few studies of its metabolism in animals have been done. In this study, we tested the hypothesis that metolachlor, which is structurally similar to alachlor, is metabolized to metolachlor mercapture in humans as alachlor is metabolized to alachlor mercapture. We synthesized metolachlor mercapture to use as a standard to determine whether the urine samples from subjects who had been occupationally exposed to metolachlor contained metolachlor mercapturate.