Ion-Exchange Chromatography Columns

Ion-exchange chromatography, sometimes called ion chromatography (IC), is a chromatography method used in chemistry to separate mixtures based on their ionic charges. The process requires a column prepared with a substance called a resin, which typically consists of cellulose, agarose, or polymeric beads with charged functional groups of chemical compounds attached. The resin must have the opposite charge as that of the sample. The sample flows through the column, and the charged molecules bind to the resin, causing the components of the mixture to separate. Elution with a mobile phase, typically a salt, releases the individual components of the sample so that they can be analyzed. In analytical chemistry, ion-exchange chromatography is commonly used to purify proteins, peptides, nucleic acids, and other charged molecules.

In anion exchange chromatography, one type of ion-exchange chromatography, the particles of the sample are negatively charged and require a positively charged resin. The reverse is true for another type, cation exchange chromatography: Cations are positively charged and require a negatively charged resin for the separation process.

Ion chromatography columns (or IC columns) may be made of glass or plastic such as polypropylene. Many are designed for use with autosamplers in ion chromatography systems, though some are designed for use in manual tests. Columns come in varying lengths and inner diameter dimensions. Some are pre-packed with resin. A variety of resins is available, and each is suited to particular ion chromatography tests.

Considerations for choosing a column depend on the type of sample and level of purification to be achieved, as well as the type of resin and its capacity. The capacity refers to the number of ion exchange groups available in the resin, sometimes given as milliequivalents per gram dry or per milliliter wet of ion exchanger. An ion exchanger in a resin can be called either strong or weak, depending on how the pH of the sample and buffer solution affects its charge.