Investigation under ionizing radiation of An-ligand complexes in solution by electrospray ionization mass spectrometry
Résumé
In nuclear fuel reprocessing, the organic ligands in solution are subjected to radiolysis. The resulting effects of radiolysis can lead to modifications of the solution composition. These changes can alter the extraction properties of the ligands, specifically, their extraction efficiency and selectivity. Therefore, it is important to study the effect of radiolysis on the speciation of the complexes in solution to identify the weak points in the molecular structure of the ligands. This identification can facilitate the design of more stable molecules and of molecules that generate innocuous degradation products. The aim of this work is to increase the understanding of ligand behavior when exposed to ionizing radiation. The dialkyl monoamide class of extractants has been chosen for this study. The formation of simple carboxylic acids as well as amine degradation products of some dialkyl monoamides have been characterized by potentiometry, FTIR and/or GC-MS [1]. While these techniques are useful in identifying the main families or lower molecular weight products, electrospray ionization mass spectrometry is a powerful technique that can be used to identify products through both charge and mass characterization. This is especially useful when trying to determine complex formation between degradation products and metal ions. This work aims to characterize the degradation products formed as a result of alpha radiolysis of monoamide extractants involved in plutonium complexes by electrospray ionization mass spectrometry. In addition to in-situ alpha irradiation, non-complexed extractants have been irradiated by a gamma source allowing direct comparisons to be made between the type of irradiation and the resulting degradation products that form. To investigate the effect of the structure on the stability of the ligand, in particular, the effect of the alkyl group on the carbonyl function, three extractants were chosen, N, N-di-(2-ethylhexyl)butryamide (DEHBA), N, N-di-(2-ethyhexyl)isobutyramide (DEHiBA), and N, N-di-(2-ethylhexyl)-3, 3-methylbutyramide (DEHDMBA).