SURFACE-DIFFUSION PHENOMENA IN REVERSED-PHASE LIQUID-CHROMATOGRAPHY WITH METHANOL WATER AND ACETONITRILE/WATER MIXTURES/

Characteristics of surface diffusion phenomena were studied under low- loading or analytical conditions of reversed-phase Liquid chromatograp hy. As mobile phases, methanol/water and acetonitrile/water mixtures w ere used. In both systems, several similar relationships were confirme d for the enthalpy-entropy compensation effect, the linear free-energy relation, and some correlations between the surface diffusion coeffic ient, D-s, and mobile-phase composition, phi, and between the ratio of D-s to molecular diffusivity and phi. Similarity of the correlations indicated that the surface diffusion mechanism was essentially identic al irrespective of the type of the organic modifiers. A strong influen ce of phi on D-s was confirmed. A nomograph concerning corresponding m obile-phase compositions for D-s as well as for adsorption equilibrium constant was proposed for the both mobile-phase systems. On the basis of the several correlations, D-s under various conditions in low-conc entration systems can be estimated.