Use of Electro-spray Ionization Mass Spectrometry (ESI-MS) for the characterization of complexes 'ligand - metallic cations' in solution

In the framework of nuclear waste reprocessing, separation processes of minor actinides from fission products are developed by Cea. In order to understand the mechanisms involved in the extraction processes, the 'ligand/metallic cation' complexes, formed in the organic phases are characterized by electro-spray-mass-spectrometry (ESI-MS). This paper deals with the extraction of lanthanides (III) and americium (III) cations by an organic phase composed of a malonamide or / and a dialkyl phosphoric acid, diluted in an aliphatic diluent. For the dialkyl phosphoric acid, Ln(DEHP)3(HDEHP)3 complexes are observed and in the presence of a large excess of Ln(NO3)3, dinuclear species are also observed. For the malonamide extractant, it appears that the complexes formed in the organic phase are of the Nd(NO3)3Dx type, with 2 ≤ x ≤ 4: their distributions depend on the ratio [Ln]/[DMDOHEMA]. When the two extractants are present in the organic phase, mixed 'Ln-malonamide-dialkyl phosphoric acid' species are observed. The influence of several parameters, such as extractant concentration, solute concentration, aqueous acidity and the nature of the cations (lanthanides or americium) are studied. (authors)