ESI-MS speciation analysis of neodymium and thorium complexed with nitrilotriacetic and picolinic acids

Abstract

The complexing agents co-diposed in nuclear waste must be studied as possible responsible for the solubilization and transport of radionuclides in the environment. The importance of these complexing agents will depend on the sources, the impacted environment and the concentrations of metals and complexing agents present. Ethylenediaminetetraacetic (EDTA), nitrilotriacetic (NTA) and picolinic (PA) acids are among the most used chelating agents in chemical decontamination of nuclear facilities. In this context, we have focused on the speciation analysis of lanthanides and actinides with EDTA, NTA and PA by ESI-MS. In this work, we made ESI-MS speciation analysis of synthetic samples of Nd and Th with NTA and PA. We investigated system response as a function of ligand/metal ratios and of solution pH. Our results were contrasted with those found in the literature and those predicted by speciation softwares.We contributed to the speciation analysis of PA complexes with Ln and An, for which published studies are very scarce. Th-PA species with stoichiometries 1:1, [ThPA]3+ to 1:6, [ThPA6]2− were observed. The 1:1 species showed its prevalence under most conditions studied. PA showed to form complexes with Nd with stoichiometries 1:1, [NdPA]2+ to 1:4, [NdPA4]−. The 1:3 species seems to gain dominance as PA concentration increase. Speciation analysis of Th and Nd with mixtures of ligands and in a spiked real sample is also presented.