Para-aminophenyl alumina: A new stationary phase for high-performance liquid chromatography

Surface-modified alumina containing covalently-bonded p-aminophenyl groups was prepared by refluxing chromatographic grade alumina with p-aminophenylphosphonic acid in n-butanol. The resulting material, p-aminophenylalumina (PAPA), was evaluated for use as a stationary phase in high performance liquid chromatography (HPLC). When used with mobile phases consisting of acetonitrile and water, retention of solutes on the PAPA phase exhibited normal phase behavior, as evidenced by the increases in solute retention times with increasing percentages of acetonitrile. Excellent separations of carbohydrate mixtures were obtained on the PAPA stationary phase. Comparisons of the chromatographic properties the PAPA phase with those of commercial aminoalkyl silica stationary phases were also performed.