Surface and structural properties of silica gels used in high performance liquid chromatography

Complete nitrogen adsorption-desorption isotherms were measured over the entire pressure range including the region of very low pressures for a series of silica gels used in high performance liquid chromatography. In addition to standard characterization of the silicas studied, which included the evaluation of the specific surface area and the total pore volume, the experimental adsorption isotherms were used to calculate the adsorption energy distributions and the pore volume distributions by employing an advanced numerical algorithm based on the regularization method. For most silica samples studied, the resulting energy distributions are similar indicating that their surface properties are analogous. For some silicas, which are able to chemisorb greater amounts of water as shown by supplementary thermogravimetric studies, the adsorption energy distributions are different. Analysis, of the resulting pore volume distributions for most silicas studied, shows a relatively narrow range of mesopores and no substantial evidence for the presence of micropores.