Determination of accessible silanols groups on silica gel surfaces using microcalorimetric measurements

The calorimetric measurements of methanol and hexane heats of immersion were carried out on different silica gels. Based on the difference in immersion heats, a methodology for the determination of the number of silanols on the surface is presented. The calculated concentration of residual silanols on the silica gel surface agreed with data found in the literature. The proposed methodology, based on a calculation of possible hydrogen bond formation, was also tested on the series of bonded stationary phases with different coverage densities. A very good correlation between the calculated number of accessible residual silanols and the coverage density of bonded ligands was observed.