Determination of dicamba and 2,4-D in water and soil by isotope dilution GC/MS

Abstract

An isotope dilution GC/MS technique for the analysis of low part per billion (ppb) concentrations of dicamba and 2,4-D in water and soil is described. Known amounts of stable-labeled isotopes such as dicamba-d, and 2,4-D-d3 are spiked into each sample prior to extraction. Water samples are extracted with methylene choride at pH 51; soil samples are extracted with acetone-hexane at pH 51. Analysis is performed by high-resolution GC/MS, with the mass spectrometer operated in the selected ion monitoring mode, following derivatization of extracts with pentafluorobenzyl bromide. Accuracy greater than 84% and precision better than 19% were demonstrated with spiked samples. This technique has been used successfully in the analysis of over 300 water and 300 soil samples. Detection limits of 0.1-1.0 ppb for waters and 1-10 ppb for soils were achieved by selected ion monitoring GC/MS.

Evidence for thermal decomposition contributions to the mass spectra of chlorinated phenoxyacid herbicides obtained by particle beam liquid chromatography mass spectrometry

“…Phenoxyacid herbicides are compounds that have presented difficulties in GC analyses. Analytical methodology for these compounds has relied on the use of derivatization steps prior to GC with electron capture detection [2][3][4][5]. In an attempt to avoid the derivatization step, researchers have recently applied LC/MS methods to the analysis for phenoxyacid herbicides.…”

Analysis of dicamba from water using solid-phase extraction and ion-pair high-performance liquid chromatography

“…The procedure is sensitive (1.6 ppb) and applicable to multiple samples, eliminates the need for costly and environmentally hazardous solvents, and does not require any solvent evaporation steps.Dicamba (3,6-dichloro-2-methoxybenzoic acid) is a postemergence herbicide used for the control of broad-leaf weeds in cereals and grasslands. Established methods of dicamba analysis involve its extraction from acidic aqueous media with diethyl ether followed by derivatization and gas chromatographic analysis (Devine and Zweig, 1969; Garbrecht, 1970; Chau and Terry, 1976;Agemian and Chau, 1977;Lopez-Avila et al, 1986). However, these procedures are time-consuming and require expensive pesticide-grade solvents.…”