Affinity chromatography is a very effective method for protein purification. The separation mechanism is based on the specific interaction between proteins and certain molecules. In addition to biological specific support (such as enzyme substrates, antibodies, receptors, etc.), some commonly known as biological ligands (such as lectin, dye) are also used in affinity chromatography, and affinity chromatography on immobilized metal ions is increasingly important in the separation and purification of proteins and peptides. Affinity chromatography is very selective and efficient.