Ion exchange chromatography is a common technique for protein purification and separation, which achieves separation based on the charge differences between molecules and the resin. The chromatographic medium carries fixed charged groups and can adsorb target molecules of opposite charge. By adjusting the pH and salt concentration of the buffer to alter binding affinity, impurities and target proteins are eluted stepwise. Featuring mild operating conditions and high efficiency, it is widely used in the purification of biological samples such as recombinant proteins and antibodies.