Determination of the fractions of the stoichiometric displacement parameter Z.

Based on the stoichiometric displacement theory for adsorption (SDT-A) of solute, an equation expressing the linear relationship between the affinity of the solute to the adsorbent (beta a), and the logarithm of the molar concentration of the solvent in bulk solution (log alpha D), was derived. The terms n and q values (moles of the solvent separately released from the adsorbent and solute as one mole of solute is adsorbed), that are the fractions of the stoichiometric parameter Z (Z = n + q), were obtained from this quantitative relationship. The derived equation was tested by the derivatives of benzene under different methanol concentrations by frontal analysis of reversed-phase liquid chromatography (RPLC) and satisfactory results were obtained. Moreover, the terms n and q were tested with the presented method, and also examined by the combination of the SDT-A with stoichiometric displacement theory for retention (SDT-R). Both n and q were further validated to follow the homologue rule. More moles of the solvent were released by the adsorbent than by the solute (n > q) and the n value increases when the group attached to benzene was nonpolar.