SELECTIVITY OF CARBON PACKING MATERIALS IN COMPARISON WITH OCTADECYLSILYLSILICA AND PYRENYLETHYLSILYLSILICA GELS IN REVERSED-PHASE LIQUID-CHROMATOGRAPHY

The retention selectivity of graphitic carbon packing materials was compared with those of octadecylsilyl- and pyrenylethylsilylsilica packing materials in reversed-phase liquid chromatography. A carbon stationary phase showed the highest hydrophobicity and selective retention of planar, unsaturated compounds. The presence of hydrophilic groups did not cause as great a retention decrease on carbon as on silica-based materials. A much greater influence of structural planarity of solutes on selectivity was observed with carbon than with silica-based phases, presumably because the solute planarity emphasizes the interaction with the graphite surface based on charge transfer and dispersion forces. Pyrenylethyl-bonded silica gel was found to be intermediate between alkylsilica and graphitized carbon packing materials with respect to the selectivity based on the electronic and steric interactions with the fused-ring aromatic systems on the stationary phase.