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Comparison of Silica-, Alumina-, and Polymer-Based Stationary Phases for Reversed-Phase Liquid Chromatography

A comprehensive chromatographic evaluation of four pH-stable analytical-scale reversed-phase columns is presented. The following columns are investigated in this study : Unisphere-PBD, γRP-1, PRP-1, and Deltabond C 8 . The columns are evaluated in terms of reduced plate height, reduced eluent linear velocity, column flow resistance, peak asymmetry, selectivity, total porosity, and the Knox-Parcher ratio. Deltabond C 8 is found to be the most efficient column followed by yRP-1, Unisphere-PBD, and PRP-1. All columns except PRP-1 remain well below a flow resistance value of 1000 at flow rates between 0.5 and 4.0 mL/min. Excluding PRP-1, the columns show excellent peak symmetry (A s < 1.2). With respect to selectivity, all columns except γRP-1 have adequate selectivity for the analytes in the test mixture. The total porosity for the columns yields a value of about 0.77 for the alumina particle columns, 0.67 for the silica particle column, and 0.60 for the polymeric particle column. The Knox-Parcher ratio for each of the four columns indicates that the centrally injected solute would not reach the walls before exiting the column. The low dependence of column pressure drop on flow rate for the Unisphere-PBD suggests that it may be ideal for preparative-type separations. Highlighting the capability of the Unisphere-PBD are representative applications in the areas of pharmaceuticals and natural products, including purines and pyrimidines, PTH-amino acids, peptides, catecholamines, fat soluble vitamins and derivatives, and analgesics.