Returning the packing in the column to its initial state after gradient elution. Mobile phase is passed through the column stepwise or in a gradient. The stationary phase is solvated to its original condition. In ion-exchange chromatography, regeneration involves replacing ions taken up in the exchange process with the original ions that occupied the exchange sites. Regeneration can also refer to bringing back any column to its original state (e.g., the removal of impurities with a strong solvent).