Larry F. Wieserman

Assessment of Mobile Phase Flow Resistance of Fused Microplatelet Alumina-Based Stationary Phases for Reversed Phase High Performance Liquid Chromatography

Abstract The mobile phase flow resistances (φs) of several stationary phases consisting of surface-modified UnisphereTM fused microplatelet alumina particles were determined and compared with corresponding values obtained from stationary phases based upon more conventional spherical and angular silica and alumina particles. Although the φ value obtained for a fused-microplatelet alumina-based phase was slightly lower than the value obtained on a spherical alumina-based phase with similar particle dimensions and surface modification, factors other than particle shape were found to have a substantial effect on mobile phase flow resistance. Larger φ values were obtained with phases with smaller average particle diameters. These were attributed to the presence of greater numbers of microparticles with diameters less than 5 microns in such phases. Larger φ values obtained for wide pore (21 nm) and octyl-bonded alumina-based phases over narrow pore (11 nm) and octadecyl-bonded phases were attributed to the for...

Evaluation of octadecyl-bonded alumina for separations of proteins and peptides by reversed-phase high-performance liquid chromatography

SummaryA recently-developed octadecyl-bonded alumina (ODA) stationary phase was evaluated for the separation of peptides and proteins by reversed phase high performance liquid chromatography. Using standard water-acetonitrile mobile phase gradients containing 0.1 % trifluoroacetic acid, the average peak capacity obtained for the separation of a mixture of ribonuclease a, cytochrome c, lysozyme and carbonic anhydrase on an ODA column are similar to that obtained on a widely used octadecylsilane (ODS) column. However, overall chromatographic resolution of the components of this mixture on ODA is inferior to that obtained on ODS. Cytochrome c peak areas were found to be ∼50% smaller on the ODA column than on ODS. On the other hand, both peak capacities and resolutions of octapeptide mixtures were found to be generally superior on the ODA column, and peak areas for a representative octapeptide were found to be virtually identical for both ODA and ODS columns. The differences in the results obtained on the ODA and ODS columns for these separations are attributed to the smaller pore size and unique fused-microplatelet shape of the ODA particles. Comparisons of the separations of the tryptic digest of cytochrome c on the ODS and ODA columns demonstrate that the ODA phase is potentially as useful as ODS for peptide mapping applications.

Perfluorooctyl and Perfluorobutyl Bonded Alumina Stationary Phases for High Performance Liquid Chromatography

Abstract The preparation and properties of perfluorooctylalumina (PFOA) and perfluorobutylalumina (PFBA) high performance liquid chromatographic stationary phases have been investigated. The PFOA phase was produced by chemisorption of perfluorooctanoic acid onto the surface of alumina. The PFBA phase was produced by a similar adsorption of perfluorobutylphosphonic acid onto alumina. Both phases exhibit reverse phase liquid chromatographic properties. Elemental analyses of these materials indicated that alkyl group surface coverage of the PFBA phase is higher than that of the PFOA phase. In contrast, retention of solutes on the PFBA phase is lower than that of PFOA. Isocratic capacity factors of over 20 compounds on the PFOA and PFBA phases were determined and compared with those obtained on octadecylalumina (ODA) and octadecylsilica (ODS) phases. In contrast to the greater retention of phenols than other compounds that was evident on the unfluorinated ODA phase, the retention of phenols on the PFOA and PF...