Thin-layer chromatographic behaviour and separation of rare earths on silica gel in aqueous ammonium sulfate solution

The thin-layer chromatographic behaviour of all the rare earths except promethium on silica gel in aqueous ammonium sulfate solutions of varying concentrations has been investigated. Generally, the Rf-values of each rare earth except scandium increase with increasing concentration of the salt, and those for the lanthanoids decrease in a regular way with increasing atomic number (Z). At lower salt concentrations, the tetrad effect pointed out by Peppard et al. is clearly found in the variations of both the Rf-values and the logarithm of the separation factors relative to Gd with Z. The present system permits good separations of adjacent pairs of the lanthanoids, especially heavier ones (Ho to Lu), from each other. Typical chromatograms for the separation of multi-component mixtures are presented. (orig.)