Solvent effects on the complexation of trivalent lanthanide cations by sugars and alditols: Chromatography-calorimetry comparison

A study of the solvent effects on the relative stabilities of the complexes formed between some polyols (sugars and alditols) and lanthanide cations has been performed by thin-layer ligand-exchange chromatography. The Rf values of arabinose, ribitol, ribose and glucitol in binary aqueous mixtures have been measured on TLC plates in the La3+ and Sm3− forms. Mixtures of water with 5 to 30 wt% Me2SO, acetonitrile, methanol, or tert-butanol were used as eluents. The modification of the polyols separation upon addition of the organic component has been examined. Furthermore, in order to compare the chromatographic and thermodynamic behaviours of the complexes, the stability constant for the complexation of Sm3+ by glucitol has been determined in the different binary mixtures using a flow microcalorimeter.