Utilization of the functional group contribution concept in liquid chromatography on chemically bonded reversed phases

Abstract

The possibilities of utilizing the UNIFAC group model of activity coefficients for the prediction of reversed-phase liquid chromatographic retention data are discussed. Provided that the retention of a solute i is due to liquid-liquid partition, the retention constant (ln ki) is related to the activity coefficient of the solute in the mobile phase (ln γim) by ln ki = ln γim + constant. By comparison of experimentally observed ki and calculated γim values, it is shown that for certain solutes the UNIFAC concept can be used for the calculation of changes in solute retention with alterations in mobile phase composition, and for a rough estimation of absolute retention indices. By correlating ki and γim values, it is possible to calculate the phase ratio of the chromatographic system and the activity coefficient of a solute in the stationary phase. © 1985.