Chromatographic study on liquid‐phase adsorption on octadecylsilyl‐Silica Gel

Adsorption characteristics of reversed‐phase liquid chromatography and influence of solvent composition on the characteristics are studied by the chromatographic method and the moment analysis. Adsorption equilibrium constant increases by adding hydrophobic increments into adsorbate molecules. Contributions of fluid‐to‐particle mass transfer and intraparticle diffusion to mass‐transfer resistance in the octadecylsilyl‐silica gel (ODS) column are almost equally great. Surface diffusion is dominant for the intraparticle diffusion in ODS. The logarithm of the surface diffusion coefficient linearly increases with an increases with an increase in methanol fraction in the range from 40 to 100 vol. %. In liquid‐phase adsorption, activation energy of surface diffusion is greater than the isosteric heat of adsorption and both increase when methanol fraction decreases in the range from 40 to 100 vol. %. An empirical correlation based on experimental data proposed estimates surface diffusion coefficients from physical properties of adsorbates.