Multisolute adsorption equilibria in a reversed-phase liquid chromatography system

Abstract Multisolute adsorption equilibrium data are reported for benzyl alcohol, 2-phenylethanol and 2-methyl benzyl alcohol in a reversed-phase system. The adsorption data acquired exhibit very good thermodynamic consistency. The thermodynamic functions of adsorption were derived from the single-solute adsorption data measured at different temperatures. The values of the isosteric heats of adsorption suggest a nearly homogeneous surface for the adsorbent (octadecyl bonded silica) under consideration. A nonideal adsorbed solution theory model is applied to the experimental data. The model provides an excellent prediction of the multisolute adsorption equilibria based on the parameters derived from the single-solute adsorption data. Liquid–liquid equilibrium models were also used to describe the experimental data. In this case, the best representation of the experimental data is obtained when using 1-decanol to represent the stationary phase. Although the partition model provides a satisfactory representation of the experimental data at low concentrations, it fails to represent the curvature of the equilibrium data at higher concentrations of the solutes. The latter model is also unable to describe the temperature dependence exhibited by the single-solute adsorption data.