Effect of silanol groups on heat-treated silicas by calcination and retention behaviour in high-performance liquid chromatography

Abstract

The effect of silanol groups on heat-treated silicas by calcination has been studied by high-performance liquid chromatography. After heat-treating at various temperatures, the silicas were used for the measurement of physical parameters and chemical analysis. From elemental analysis data for carbon and hydrogen, the reactive silanol group concentrations, α OH(S), were determined to be 2.3% from C or 2.9% from H for 180°C-treated silica, and 1.6% from C or 1.6% from H for 950°C-treated silica (original silica: mean pore diameter 11.6 nm, specific surface area 298 m 2/g, pore volume 1.22 ml/g, particle size 5.0 μm). The capacity factors of dioctylphthalate, dibutylphthalate and dimethylphthalate generally increased with increasing-heat treatment from 180 to 950°C, using methanol—hexane mixtures as the eluent. On the basis of the physico-chemical and chromatographic data the heat-treated silicas by calcination have been compared.