Regional Water-Quality Analysis of 2,4-D and Dicamba in River Water Using Gas Chromatography-Isotope Dilution Mass Spectrometry

Abstract

Gas chromatography with isotope dilution mass spectrometry (GS-MS) and enzyme-linked immunosorbent assay (ELISA) were used in regional National Water Quality Assessment studies of the herbicides, 2,4-D and dicamba, in river water across the United States. The GS-MS method involved solid-phase extraction, derivatized with deuterated 2,4-D, and analysis by selected ion monitoring. The ELISA method was applied after preconcentration with solid-phase extraction. The ELISA method was unreliable because of interference from humic substances that were also isolated by solid-phase extraction. Therefore, GC-MS was used to analyze 80 samples from river water from 14 basins. The frequency of detection of dicamba (28%) was higher than that for 2,4-D (16%). Concentrations were higher for dicamba than for 2,4-D, ranging from less than the detection limit (<0.05Î/L) to 3.77 Î/L, in spite of 5 times more annual use of 2,4-D as compared to dicanba. These results suggest that 2,4-D degrades more rapidly in the environment than dicamba.

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Thurman, E.M., Zimmerman, L.R., Aga, D.S., and Gilliom, R.J., 2001, Regional Water-Quality Analysis of 2,4-D and Dicamba in River Water Using Gas Chromatography-Isotope Dilution Mass Spectrometry: International Journal of Environmental Analytical Chemistry, v. 79, no. 3, p. 185-198.

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