Column packing:
The column packing consists of a neutral polymer core of ~ 10 µm diameter depending on whether the packing will be used for the separation of cations or anions. Contrary to the conventional ion-exchange chromatography where core is sulphonated or aminated leading to the formation of sulfonic acid or quaternary amine groups, within ion chromatography, a monolayer of aminated or sulphonated polymeric anion exchange beads is used.
Similarly, for a cation exchanger and there would be an intermediate layer of aminated groups covered by a thin layer of sulphonated resin beads. Due to the proximity of all the active sites to the eluent-resin interface, this type of exchanger has favorable mass transfer characteristics. It has low exchange capacity, about 0.020 meq/g of copolymer. In most applications, silica based materials are inappropriate due to their degradation in the presence of aqueous eluents and their poor selectivity for some ionic species. The eluent passes through a suppressor column where the eluting or background electrolyte is effectively removed by converting it into water or, water and carbon dioxide i.e., sodium ions are replaced by hydronium ions or methylsulfonate ions with hydroxyl ions.
A miniaturized 'self-regenerating' suppressor cartridge incorporating an electrolysis cell is also available where H3O+ and O2 are continually formed by the electrolysis of a stream of deionized water passing through an anode compartment and similarly, OH¯ and H2 are formed in a cathode compartment. Both compartments are separated from the eluent either through cation or anion- exchanges membranes depending on whether anionic or cationic analytes are to be separated.