Ion exchange resins

Ion exchange chromatography

Ion exchange chromatography (IEX) is the separation of biomolecules based on their total ionic charge. Using the chromatographic separation technique, you can separate similar types of biomolecules, as this technique allows you to manipulate the charge carried by the biomolecules of interest by altering buffer pH. Common applications of IEX are the capture or polishing of peptides, proteins, amino acids, and nucleotides for analytical or preparative purposes. Based on the environmental pH, proteins may carry a net negative charge, net positive charge, or no net charge. The pH at which a molecule contains no net charge is its isoelectric point (pI). Advantages of IEX chromatography include:

• IEX allows high flow rates for use in industrial chromatography applications
• IEX concentrates samples
• IEX provides high yields
• IEX buffers do not denature cells

Ion exchange resins

IEX resins carry charged functional groups immobilized to resin beads to attract biomolecules with the opposite charge. When using a buffer with a pH greater than the pI of your target protein, the protein carries a negative charge, requiring positively charged anion exchange resins. In a buffer with a pH value that’s lower than the pI of your target protein, the protein carries a net positive charge, so you will need a negatively charged cation exchange resin.

After loading your IEX chromatography column with a sample at a specific pH, appropriately charged proteins bind to the resin.

Ion exchange resin selection

IEX resins comprise positively or negatively charged functional groups, which come covalently bound to solid matrices such as agarose, cellulose, polystyrene, and polymethacrylate. When choosing IEX resins, consider the following factors:

• Whether you need an anion exchanger or cation exchanger
• Whether you need a strong or weak ion exchanger
• Resin particle size
• Chromatography flow rates
• Resin dynamic binding capacity

Ion exchange resins are available from Cytiva in bulk or in prepacked columns.

Types of ion exchange chromatography

Anion exchange chromatography (AEX) uses positively charged IEX resins to capture molecules with net negative surface charges. Cation exchange chromatography (CEX) uses negatively charged IEX resins. AEX and CEX chromatography can separate a wide range of biomolecules, supporting use for preparative or analytical purposes.

Ion exchange resins FAQs

Here are answers to some frequently asked questions about IEX resins.

How does ion exchange work?

Ion exchange chromatography separates molecules and ions based on electrostatic interactions with ion exchangers. IEX works on many charged biomolecules, including amino acids, nucleotides, and large proteins.

What are ion exchange resins made of?

Like other liquid chromatography resins, IEX resins can be made from various base matrices, including cellulose, agarose, dextran, and acrylamide. The base matrix is then coupled to an ion exchange ligand.

How are ion exchange resins used?

Use IEX resins to separate, capture, or polish biomolecules.

How should I choose a chromatography resin or an ion exchange resin for my application?

You can use our Purify web app to help choose a resin for your needs.