on exchange chromatography is a method to separate biological molecules by means of electrostatic interaction. It is widely used in biopharmaceutical downstream processes to purify proteins such as rhEPO. The requirements for injectable biologics are at the highest standard compared to other biologics applications. To meet such standard, the ion exchange chromatography can be applied to various stages of rhEPO purification. Anion exchange column shown to have versatility to be placed in capture and intermediate stages. In addition, anion exchange has a cost advantage if applied in capture stage. Meanwhile, cation exchange columns have limited use for this application.