Property is responsible for the separation of lanthanides:

The hydrous oxides of polyvalent metals prominent show anion exchange properties below a certain pH. They are basically amphoteric exchangers.

The separation of lanthanides is based on lanthanide contraction. This means that the crystallography radii decreases from La to Lu but the hydrated radii increases in the same order. Thus, the order of elution from a cation exchanger follows the order Lu to La. This trend is enhanced by the use of complexing agent at an appropriate pH. The complexing agents prefer the bare ions and thus, enhance the tendency of the ions to elute in the order Lu-La. Among the useful ligands are citrate, α-hydroxybutyric acid and EDTA.