Principles and Practice of Chromatography - Molecular Forces and Chromatographic Selectivity > Separations Based on Ionic Interactions > Page 35

Separations Based on Ionic Interactions

Ionic materials are not volatile under the conditions normally employed in GC, so, ionic interactions cannot be exploited in GC stationary phases to control retention. However, they are very important in LC, and ion exchange chromatography (the name given to LC separations that employ ionic interactions to control retention) is widely used to analyze ion mixtures. The use of ionic interactions to separate some alkali and alkaline earth cations is shown in figure 16.


Courtesy of Whatman Inc.

Figure 16 The Separation of Cations by Ion-Exchange Chromatography

The column used was IonPacCS12 (a proprietary cation exchange column) and the mobile phase was a 20nM solution of methanesulfonic acid in water. The flow rate was 1 ml/min. and 25ml of sample was injected. The separation almost exclusively involved ionic interactions as any dispersive interactions between a metal ion and the stationary phase would be very small indeed.