What are the types of ion-exchange resins?

Ion-exchange resins are a network of hydrocarbons formed by organic polymers, to which charged functional groups, who are the ion exchange sites, are affixed. These functional groups readily attract biomolecules of the opposite charge.

There are two main types of ion-exchange resins: cation exchange resins and anion exchange resins. Cation exchange resins are negatively charged which are used for separating cation analytes. Anion exchange resins, on the other hand, are positively charged for anion analytes.

Ion-exchange resins are also categorized as “strong” or “weak” exchangers. The categorization is not related to the strength of ion binding, but based on the extent that the ionization state of the functional groups varies with pH. Strong exchangers, such as quaternary ammonium (Q) and sulfopropyl (SP), remain fully charged over a broad range of pH, showing no variation in ion exchange capacity, which makes optimization of separation simpler. Weak exchangers, like diethylaminoethyl (DEAE) and carboxymethyl (CM) can only be ionized over a limited pH range. Weak exchangers usually have better selectivity than the strong ones because of this added variation in ionization.