How does ion-exchange chromatography separate positive and negative ions?

Ion-exchange chromatography separates ions based on their varying affinities for oppositely charged sites on an insoluble stationary phase, typically a synthetic resin. The process relies on strong electrostatic forces that attract ions to sites with the opposite electrical charge.12

The separation is achieved using specific types of resins:

• Cation-exchange resins: These contain negatively charged sites, which allow them to bind and separate positive ions (cations).1
• Anion-exchange resins: These feature positively charged sites, which are used to bind and separate negative ions (anions).1

As a mixture of ions flows through the column, those with a greater affinity for the resin's charged sites are held back more strongly, while those with less affinity move through the column more quickly. This differential migration results in the resolution of the mixture into separate bands, allowing for the precise separation and purification of various substances.314