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We have obtained retention data of benzene, toluene, ethylbenzene, phenol, and acetophenone at 25, 30, 35, 40, 45 and 50 ℃ in 30/70, 40/60, 50/50, 60/40, 70/30, and 80/20 (v/v %) methanol/water eluents using a C18 phase with a high ligand density. We drew van't Hoff plots from the data, and computed enthalpies and entropies of solute transfer from the mobile to the stationary phase. The cavity formation effect was found the major factor that governs the solute distribution between the mobile and stationary phases. The hydrophobic effect became significant in highly aqueous mobile phases. We also concluded that the Shodex C18-5B stationary phase was a polymer-like phase with a high ligand density, and followed a partially adsorption-like mechanism.
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