Chromatographic framework for analysing lithium perchlorate salt dependence on solute binding mechanisms to porous graphitic carbon surfaces

A general model to describe the lithium perchlorate salt effect on both phenol derivative-porous graphitic carbon (PGC) association and the selectivity process is presented. Thermodynamic functions of solute transfer from mobile phase to PGC surface were determined. Variation plots of solute transfer data versus lithium perchlorate concentration W in the bulk solvent indicated a change in both the solute-PGC association and selectivity mechanisms. Enthalpy-entropy compensation reveals that this association process is independent of the molecular structure of phenol. This study shows the importance of taking into account, (a) salvation by lithium perchlorate in the bulk solvent and (b) possible perchlorate-anion adsorption on porous graphitic carbon in order to determine optimum conditions for separation of phenol derivatives in this system.