Affinity chromatography has a special place in purification of biological macromolecules. The growing popularity of biopharmaceuticals, especially those derived from recombinant processes, will almost certainly require major developments in high pressure stationary phases for affinity chromatography.

This mode of separation, as the name suggests, uses stationary phases with a special affinity for a specific analyte. The affinity ligand immobilised on the stationary phase varies dramatically from peptide, to protein, to oligonucleotide, to monoclonal antibody. In some cases the target molecule is labelled with an affinity tag to simplify the separation. This approach is common in synthesis of recombinant proteins where the system can be engineered so that the target biomolecule expresses a tag such as polyhistidine. A stationary phase functionalised with aminodiacetic acid and nickel chelate is then used to fish out the required molecule by chelating with the polyhistidine tag.

Existing stationary phases used in this area are usually soft gels that often suffer from low loading capacity brought about by the inability of biological macromolecules to penetrate the matrix. The most likely progress in this arena over the forthcoming years will be in development of macroporous media with high loading capacities and the mechanical rigidity essential for operation at high pressure.