ion exchange

The process by which an anion in a mobile (liquid) phase exchanges with another anion previously bound to a solid, nonmobile, positively charged phase, the latter being an anion exchanger. For example, the process takes place when Cl^- is exchanged for OH^- in desalting. The reaction is Cl^- (in solution) + (OH^- on anion exchanger⁺) → (Cl^- on anion exchanger) + OH^- (in solution); in combination with the cation exchange, NaCl is removed from solution. Anion exchange may also be used chromatographically, to separate anions, and, medicinally, to remove an anion (for example, Cl^-) from gastric contents or bile acids in the intestine.

Chemical investigation in which cations or anions in the mobile phase are separated by electrostatic interactions with the stationary phase.
See also: anion exchange, cation exchange

The process by which a cation in a liquid phase exchanges with another cation present as the counter-ion of a negatively charged solid polymer (cation exchanger). Cation exchange may be used chromatographically, to separate cations, and medicinally, to remove a cation.
See also: anion exchange

The process by which an anion in a mobile (liquid) phase exchanges with another anion previously bound to a solid, positively charged phase, the latter being an anion exchanger. Anion exchange may also be used chromatographically, to separate anions, and medicinally, to remove an anion (e.g., Cl^-) from gastric contents or bile acids in the intestine.