How do you choose a buffer for ion exchange chromatography?

When choosing a buffer system for ion exchange chromatography, multiple factors should be considered, including pH, buffer concentration, and salt concentration.

• The pH of buffer should be 0.5 to 1 pH units above or below the protein’s pI to ionize protein as well as promote solubility.
• The buffer concentration should be sufficient to maintain buffering capacity, typically 25 to 100 mM.
• The ionic strength should not be too high, otherwise it may sabotage the affinity between protein and the column.