Study of polyaniline-coated silica gel as a stationary phase in different modes of capillary liquid chromatography

Abstract

Separation potential of a stationary phase based on polyaniline-coated silica gel porous spherical particles was investigated in different chromatographic modes of capillary liquid chromatography. l-Tryptophan and three of its structural derivatives with modified amino or carboxylic functionality were used to investigate the retention factor curves under different mobile phase composition including pH variation. Some retention curves pass minimum which indicates that more than one chromatographic mode can be employed to retain the relevant solute. The positional isomers of aminoacetophenone and caffeine and its demethylated analogs—theobromine and theophylline—were used as separation probes in normal phase, hydrophilic interaction liquid chromatography, and reversed phase modes. The stationary phase exhibits the mixed-mode retention mechanism; therefore, it is not easy to predict the elution order of the solutes only according to their polarity. Even slightly hydrophilic compounds can be sufficiently retained in reversed phase mode using polyaniline-coated silica gel stationary phase. All positional isomers of aminoacetophenone were separated for the first time in normal phase and reversed phase modes.