Abstract:
Rapid and accurate analytical methods are needed to assess the impacts of agricultural chemicals on soil and water resources. Solid-phase extraction (SPE) was evaluated as an alternative method to conventional liquid-liquid extraction for the quantitative analysis of the herbicide DCPA and its metabolites in ground waters. Strong anion exchange (SAX) proved to be the most effective phase for isolating the highly water soluble mono- and dicarboxylic acid metabolites in addition to the hydrophobic parent compound, DCPA. Using a gas chromatograph equipped with electron capture detection, a high degree of accuracy and precision was achieved with spike recoveries of the diacid metabolite from surface waters of 80.1 ± 2.3 %. The detection limit of the method was found to be approximately 0.05 pg/L for a 100 mL water sample. The developed method was validated by comparing the measured concentrations of DCPA and its acid metabolites in ground waters to those measured using conventional liquid-liquid extraction. In a survey of wells from Malheur county of eastern Oregon, total concentrations of the acid metabolites of DCPA in ground water ranged from less than the detection limit (0.05 μg/L) to 198 μg/L.
