INVESTIGATION OF ELUENTS FOR ION CHROMATOGRAPHY AND COMPARISON OF POLYMERIC ANION EXCHANGE COLUMNS

Six anion exchange columns were compared for retentivity and selectivity using o-phthalic and isophthalic acids as eluents. A linear relationship was found between column capacity (meg/column) and the capacity factors (k') for Cl('-), NO(,3)('-), and SO(,4)('-2) anions. The two polymeric anion exchange columns produced better chromatography than the silica based materials. Several new organic diacids were also investigated for use as eluents in single column ion chromatography. Depending upon the column used, all the diacids provided good to excellent separations for the anions tested. Adsorption of the eluent onto the non-functionalized ion exchange matrix was found to be an important criteron in eluent selection and chromatographic performance. Generally, diacids that were more hydrophobic in nature (aromatic or olefinic) were also the stronger eluents. A correlation between anion retention and the eluents' structure was found in several cases. The retention mechanism operating in anionic single column ion chromatography appears to include complex interactions or adsorption phenomena between eluent and ion exchange matrix and not solely a simple ion exchange process between eluent and sample anions.