SILANOL EFFECTS IN REVERSED-PHASE LIQUID-CHROMATOGRAPHY

A large number of butyl-, hexyl-, octyl- and octadecylsilica stationary phases were synthesized by the usual low-temperature and also novel high-temperature silylation methods. The phases were characterized by measuring their silanol concentrations, organic functional group concentrations and wettabilities and, additionally, by reversed-phase liquid chromatographic retention measurements. Unusual retention data, not expected on the basis of the solvophobic retention theory, were observed and are explained. Separation selectivity and peak asymmetry are interpreted by taking into account the surface concentrations of both the silanol groups and the organic functional groups. The peak shapr is better, but the separation selectivity is lower, when access to all silanol groups of a stationary phase is equally easy or equally difficult. © 1990.