Adsorption Equilibria of Valine, Isoleucine, and Leucine on Capcell-Pak C18 Resin

Abstract

The adsorption equilibria of valine, isoleucine, and leucine on a Capcell-Pak C18 resin were measured in the linear isotherm region using a frontal analysis method. This task was carried out at room temperature while varying the methanol content in liquid phase from 5 % (v/v) to 50 % (v/v). Based on the resultant adsorption data, the Henry’s constant, which is the ratio of solid-phase and liquid-phase concentrations at equilibrium, was determined for each amino acid and each liquid-phase composition. It was found that the Henry’s constant of valine was markedly different from those of isoleucine and leucine. In addition, the liquid-phase composition had a significant effect on the Henry’s constant of each amino acid. To describe such effect mathematically, several models were tested and their performances were compared. It was confirmed that the Abel model was the most accurate in predicting the Henry’s constant of each amino acid as a function of the liquid-phase composition. The adsorption equilibrium data and the model parameters reported in this study will be useful in the stage of optimizing a chromatographic process for separation of valine from isoleucine and leucine.