The Mechanism of Chromatographic Retention - Chromatographic Interactions > Ionic Interactions > Page 13

Ionic Interactions

Polar compounds have no net charge on the molecule, in contrast, ions possess a net charge that can interact strongly with ions having anopposite charge (usually called counter-ions). In ion exchange chromatography solutes carrying a net charge are retained by ionic interactions with counter ions situated in the stationary phase. The retentive mechanism involves simple electric forces between opposite charged ions. Ionic interactions are always accompanied by dispersive interactions and, in most cases, are also associated with polar interactions. Nevertheless, the dominant forces controlling retention in ion exchange chromatography result from ionicinteractions. Ionic interaction is depicted diagrammatically in figure 5.

Figure 5. Ionic and Dispersive Interactions