EFFECT OF SILANOL GROUPS ON HEAT-TREATED SILICAS BY CALCINATION AND RETENTION BEHAVIOR IN HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

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, alpha-OH(s), were determined to be 2.3% from C or 2.9% from H for 180-degrees-C-treated silica, and 1.6% from C or 1.6% from H for 950-degrees-C-treated silica (original silica: mean pore diameter 11.6 nm, specific surface area 298 m2/g, pore volume 1.22 ml/g, particle size 5.0-mu-m). The capacity factors of dioctylphthalate, dibutylphthalate and dimethylphthalate generally increased with increasing-heat treatment from 180 to 950-degrees-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.