Affinity chromatography is a mainstream technique for the specific separation and purification of recombinant proteins. It relies on the specific and reversible binding between ligands and target proteins. When the sample flows through the chromatography column, target proteins are adsorbed, while miscellaneous proteins flow out with the buffer. An eluent is then used to disrupt specific interactions to elute high-purity target proteins. Featuring strong specificity, excellent enrichment efficiency and simple operation, this method is widely used in the crude purification of His-tagged and GST-tagged recombinant proteins.