Ion Exchange Chromatography

The separation and purification of various elements by ion exchange chromatography takes advantage of the variation of the electrostatic bond energies of ions in solution. Thus, the two main controlling factors in ion exchange chromatography are the ionic charge (z) and the ionic radius (r). These two are combined in the ionic potential – z/r – that can be used to compare relative electrostatic bond strengths. Ions of high charge (trivalent or greater) and small radius have high electrostatic bond strength, and therefore are likely to attach strongly to an oppositely charged solid surface, whereas ions of low charge and large radius form relatively weaker electrostatic bonds. By manipulating the chemistry of the solution, ions can be separated from each other using this contrast in bond strength.