Establishing the feasibility of coupled solid-phase extraction–solid-phase derivatization for acidic herbicides

The significance of this research is that it improves analytical methodology used for organic chemicals in aqueous solutions by establishing the feasibility of heterogeneous chemical derivatization at the liquid–solid interface (i.e., solid-phase reaction or solid-phase derivatization). A solid-phase derivatization method for determining chlorinated herbicide acids was developed. Solid-phase extraction was used to concentrate and retain analytes on sorbents for subsequent solid-phase derivatization. Background interferences were removed from the chromatograms by electronically subtracting the responses of blank, nonfortified analyses from spiked samples. Two extraction sorbents (octadecyl bonded silica and polystyrene-divinylbenzene) and two derivatizing reagents (BF3–MeOH and trimethylsilyldiazomethane) were investigated. Recovery of 13 chlorinated herbicide acids—including pentachlorophenol, dinoseb, and bentazon (having a derivatizable functional group, OH or NH, bonded directly to a phenyl group); dicamba, picloram, acifluorfen, 3,5-dichlorobenzoic acid, and dacthal (having a derivatizable functional group, –COOH, bonded directly to a phenyl group); and 2,4-D, 2,4,5-T, dichlorprop, 2,4,5-TP, and 2,4-DB (having a derivatizable functional group, COOH, bonded directly to a sp3 carbon atom)—was tested. The analytical method developed was proven successful for determining acidic herbicides, except for the dacthal diacid metabolite, in aqueous samples.