Quantitative determination of the acidic metabolites of Dacthal in ground water by strong anion exchange solid-phase extraction

Abstract

Solid-phase extraction using strong anion exchange disks was evaluated as an alternative extraction method to conventional liquid-liquid extraction (LLE) for the quantitative analysis of the herbicide Dacthal (DCPA) and its mono-and dicarboxylic acid metabolites in ground water. The average recoveries of DCPA and its acid metabolites from deionized water were 93.7 & 2.6% and 85.6 f 2.5%, respectively. The detection limit of the SAX disk method is 0.05 pg/L for a 100 mL water sample. While no DCPA was detected in ground water from the Malheur River Basin in eastern Oregon, the total concentrations of the acid metabolites of DCPA in 100 mL samples of ground water ranged from less than the detection limit (0.05 to 158.2 pg/L and were in good agreement with those determined by means of conventional LLE.

Coupling Supercritical CO2 and Subcritical (Hot) Water for the Determination of Dacthal and Its Acid Metabolites in Soil

“…The dipropyl ester of the diacid metabolite was prepared from diazopropane and used as the internal standard for this study. 5 Ethyl iodide was purchased from Aldrich Chemical Co. (Milwaukee, WI). Reagent grade acetonitrile was purchased from Baxter (Muskegon, MI).…”

“…Standards of the monoacid metabolite (monomethyl tetrachloroterephthalic acid; 99.7% purity) and the diacid metabolite (tetrachloroterephthalic acid; 100% purity) were obtained from the U.S. EPA (Research Triangle Park, NC) and Ricerca, Inc. (Painesville, OH), respectively. The dipropyl ester of the diacid metabolite was prepared from diazopropane and used as the internal standard for this study …”

“…[2][3][4] In eastern Oregon, where Dacthal is applied to onions, the diacid metabolite is the principal form of Dacthal detected in groundwater obtained from domestic wells. 5,6 To assess the fate of Dacthal that is applied to soil, both parent and metabolite forms in water and soil should be considered. While rapid methods exist for the determination of Dacthal and its metabolites in water, 5,6 quantitative and rapid methods are needed to determine Dacthal and its metabolites in soils, since conventional methods require large volumes of solvent and time to process the extract.…”

“…5,6 To assess the fate of Dacthal that is applied to soil, both parent and metabolite forms in water and soil should be considered. While rapid methods exist for the determination of Dacthal and its metabolites in water, 5,6 quantitative and rapid methods are needed to determine Dacthal and its metabolites in soils, since conventional methods require large volumes of solvent and time to process the extract. For example, the conventional method for extracting Dacthal and its metabolites from soil requires 200 mL of 0.4 M HCl/acetone to extract a 20-g sample and the use of hazardous diazopropane to derivatize the acids to their ester forms.…”

“…Dacthal is typically applied to agricultural soils at 6−14 kg/ha . In the soil environment, Dacthal transforms to mono- and diacid metabolites that are more water soluble than the parent herbicide. − In eastern Oregon, where Dacthal is applied to onions, the diacid metabolite is the principal form of Dacthal detected in groundwater obtained from domestic wells. , …”