A systematic study of the desorption of different ion-pairing reagents on reversed phase thin-layers

Abstract

The absolute concentrations and the concentration distribution of different cationic ion-pairing reagents, such as tetramethylammonium bromide, tetrabutylammonium bromide, cetyltrimethylammonium bromide and trioctylmethylammonium chloride were studied after chromatographic development on physically and chemically bonded reversed-phase layers. The combination of the chromatographic conditions involved three variations. Untreated layers were chromatographed with mobile phases containing the ion-pairing reagent. Several layers were treated with the ion-pairing reagent prior to the chromatographic run, and methanol-water mixtures were used as mobile phase. In a third set of experiments both the layer and the mobile phase contained the ion-pairing reagent. The chromatographic behaviour of acid, neutral and basic model compounds were also studied. For the determination of different reagents remaining on the layer after the chromatographic run, spectrophotometric, potentiometric methods and capillary electrophoresis were used. The performance of the analytical methods was evaluated. Results obtained for the absolute concentrations and distribution of the reagents and the retention data were compared to those obtained on silica gel layers. A discussion of the retention mechanism is given.