What is ion-exchange chromatography (IXC)?

Ion-exchange chromatography (IXC) is a chromatography process that separates charged molecules based on their coulombic (ionic) interactions with the ion exchanger of a column. It can work on almost all the ionizable molecules encountered in biochemistry, including large proteins, small nucleotides, and amino acids.

IXC is classified into two types, anion-exchange and cation-exchange chromatography. Anion-exchange chromatography has positively charged stationary phase and is used for the separation of negatively charged analytes, whereas cation-exchange chromatography with negatively charged exchanger is designed for separating positively charged analytes.

The stationary phase surface of IXC displays ionic functional groups that bind with analyte ions of opposite charge. Molecules do not bind or bind weakly to the stationary phase are first to wash away. Then an eluant with altered conditions (e.g. change of ionic strength or pH) is used to elute the molecules bound to the stationary phase.