Effects of stationary phase cross-linking and ion-exchange capacity on the retention of carboxylic acids in ion-exclusion chromatography using sulfonated resins

Ion-exclusion chromatography (IEC) has been widely used in the separation of carboxylic acids, finding applications in the analysis of food and beverages, pharmaceuticals, biological samples, and acid rain samples.' The retention mechanism of carboxylic acids in ion-exclusion chromatography has also been investigated in many studies, and the factors which affect retention can be divided into three categories: analyte effects, mobile phase effects, and stationary phase effects. In IEC, the chromatographic system can be considered to consist of three phases: the mobile phase which comprises the eluent passing through the interstitial volume of the column, the stationary phase which comprises the occluded liquid trapped within the pores of the resin and the resin phase which is the solid resin network and functionalized groups.' In this mode of chromatography, the analytes being separated have the same charge as the functional group on the resin; that is, anions are separated on cation-exchange columns and cations are separated on anion-exchangec columns.