The First Analysis and Detection of the Herbicide Dimethenamid and its ESA Metabolite in Water

Abstract

Dimethenamid (2-chloro-N-(2,4-dimethyl-3-thienyl)-N-(2-methoxy-1-methylethyl)acetamide) is used for control of annual grasses and certain broadleaf weeds, primarily in corn and soybeans. Solid-phase extraction (SPE) is used to separate the ethanesulfonic-acid (ESA) metabolite from the parent compound during the elution of C18 cartridges using ethyl acetate for the parent compound, followed by methanol for the polar metabolite. The parent compound is detected using gas chromatography/mass spectrometry (GC/MS) in selected-ion mode. The ESA metabolite is detected using high-performance liquid chromatography/electrospray mass spectrometry (HPLC/ESP/MS) in negative-ion mode. The quantitation limits are 0.02 and 0.05 Îg/L from a 100-mL sample for the parent and metabolite compounds, respectively. These methods are compatible with existing methods and thus allow for analysis of popular corn herbicides and their common metabolites with one extraction. In 1999, several hundred surface-water samples were collected from the United States and analyzed for dimethenamid and/or dimethenamid-ESA. Most samples contained only trace or no detectable amounts of dimethenamid, with detections in the 0.02 to 0.90-Îg/L range. The dimethenamid-ESA metabolite was also found in some samples.

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Zimmerman, L.R., Schneider, R.J., Hostetler, K.A., and Thurman, E.M., 2000, The First Analysis and Detection of the Herbicide Dimethenamid and its ESA Metabolite in Water [abst.]: American Chemical Society, San Francisco, California, March, 26-29, 2000.

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