Ion exchange chromatography is a chromatography method achieving separation based on the different mass and quantity of electric charges on biomolecules. Macro-biomolecules contain acidic and basic functional groups, which can be changed in terms of charge property and quantity by adjustment of buffer pH. Thus, after binding between biomolecules and IEX resins (with opposite charge property of the biomolecules), biomolecules will be eluted in sequence (molecules with weaker binding will be eluted earlier) if ion strength or pH in mobile phase is altered. By this way, effective purification can be achieved.