Regional water-quality analysis of dicamba and 2,4-d in river water using gas chromatography-isotope dilution mass spectrometry

By E. M. Thurman, L.R. Zimmerman, D.S. Aga, and R.J. Gilliom 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　humic substances that were also isolated by solid-phase extraction. Therefore, GC-MS was used to analyze 80 samples　river water　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　less than the detection limit (<0.05/L) to 3.77 /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. Yangzhou pioneer chemical CO.,LTD