Extractive pentafluorobenzylation using a polymeric phase-transfer catalyst: a convenient one-step pretreatment for gas chromatographic analysis of anionic compounds

Abstract

An extractive pentafluorobenzylation procedure has been established for gas chromatographic analysis of various anionic compounds using a polymer-bound phase-transfer catalyst and pentafluorobenzyl bromide as the derivatization reagent. The efficiency of five polymer-bound catalysts was compared, and tri- n-butylmethylphosphonium bromide, polymer bound (0.75 mequ Br −/g, 200–400 mesh) was found to be the most effective. Varieties of carboxylates and phenolates in aqueous samples were readily extracted as pentafluorobenzyl (PFB) derivatives with the exception of certain compounds, such as picrate which is a weak base and sterically-hindered. The conditions for extractive derivatization for both individual and simultaneous analyses were optimized. Simultaneous derivatization could be performed under moderate conditions (i.e. at pH 6.5, 60°C). Traces of such anionic compounds, even in a relatively large volume of aqueous sample, could be efficiently captured and converted by the catalyst, and then concentrated in a small-volume organic layer as PFB derivatives.