EFFECT OF THE TYPE OF ORGANIC MODIFIERS ON MASS-TRANSFER IN REVERSED-PHASE LIQUID-CHROMATOGRAPHY

The mass-transfer characteristics were studied in a reversed-phase liq uid chromatography consisting of an octadecylsilyl-silica gel and acet onitrile/water mixture (70/30, vol), and were compared with those obta ined by using methanol/water (70/30, vol). In the two chromatographic systems, similar tendencies were observed for various adsorption chara cteristics. However, their absolute values were not entirely identical . Irrespective of the type of organic modifiers, surface diffusion was dominant for intraparticle diffusion. Similar correlations were also demonstrated with regard to the surface diffusion, i.e., the enthalpy- entropy compensation and the linear free-energy relation, suggesing a similarity in the surface migration mechanism in the two chromatograph ic systems. A few estimation procedures of the surface diffusion coeff icient were proposed.