Dynamic coating ion-exchange chromatography of cations on an octadecyl-bonded silica stationary phase

It was found that common cations (Na+, NH4+, K+, Mg2+ and Ca2+) could be strongly retained on an ODS stationary phase when aqueous solutions of carboxylic acids were used as eluents. The chromatographic conditions used in this work were the same as in common cation-exchange chromatography on a cation-exchange resin and the retention behavior of the above-mentioned cations on the ODS column was quite similar to that on a cation-exchange column. The retention behavior and mechanism have been investigated using a number of carboxylic acids as eluents. The retention mechanism of the cations in these experiments was considered to be a dynamic coating ion-exchange mechanism. The carboxylic acids in the mobile phase were coated onto the surface of the ODS stationary phase and formed a dynamic carboxylic acid functional layer which could act like the functional group layer of a carboxylic group cation exchanger.