On the Use of Spectroscopic Techniques for Interaction Studies, Part I: Complexation between Europium and Small Organic Ligands

Abstract

In the framework of environmental studies, it is important to understand the interaction of humic substances with cations (heavy metals, radionuclides) and to determine their complexation constants in order to evaluate their potential impact on their fate. For this purpose, two techniques have been used: electrospray ionization mass spectrometry, a newly used technique in speciation studies, and time-resolved laser-induced fluorescence spectrometry, a well-known technique for such studies. As a first step, for simplification purposes and to compare both techniques, simple molecules having functional groups present in humic substances have been selected, such as acetic, glycolic, and 4-hydroxyphenylacetic acids. Both techniques have been used to obtain stoichiometries and complexation constants between these simple molecules and europium (III).

Evaluation of electrospray ionisation mass spectrometry as a technique for the investigation of competitive interactions: A case study of the ternary Th‐Mn‐EDTA system

“…The total Mn‐EDTA species signal was 3 times lower than the free EDTA or Th‐EDTA signals for a similar concentration. Differences in electrospray efficiency have been reported previously for different metal complexes of a particular ligand, and, although these differences are affected by the instrumental parameters used, they mainly arise from the characteristics of the analyte . Therefore, in order to improve the response for the Mn‐EDTA species in the positive ion mode using a pre‐equilibrated solution containing equimolar Mn and EDTA (0.5 mM), the capillary voltage was gradually increased from 38 to 63 V and the tube lens offset were reduced from 21 to 11 V. This resulted in a 30% improvement in the electrospray efficiency of the Mn‐EDTA monomeric species and an increase in the monomeric to dimeric Mn‐EDTA species signal ratio.…”

Europium(III) complexed by HPSEC size-fractions of a vertisol humic acid: Small differences evidenced by time-resolved luminescence spectroscopy

“…Thus, the observed decrease of A( 7 F 2 / 7 F 1 ) may be due to both an increasing number of carbohydrate molecules, exhibiting much lower A( 7 F 2 / 7 F 1 ) value [66], and a decreasing number of aromatic molecules [23]. This varying molecular distribution during GHA fractionation modifies the indirect excitation of the central europium(III) atom via the 3 * triplet level.…”

Paramagnetic Relaxation Enhancements in Acetate and Its Fluorine Derivatives Interacting with Gd3+: Complex Formation, Structure, and Transmetallation

“…[15] A general challenge is the accurate description of the thermodynamics, structure, and kinetics of interaction of solvent and solute molecules with Ln 3 + ions in aqueous and organic solutions. The problem arises not only for the optimization of Gd 3 + based contrast agents, [16][17][18][19][20] but also for the interactions of the radioactive trivalent actinide ions Am 3 + and Cm 3 + with humic substances modelled by those of Ln 3 + with simple species [21] and for the difficult liquid-liquid separation of these actinide ions from the Ln 3 + ions [22,23] during the reprocessing of the used nuclear fuel. In-depth theoretical efforts have been devoted to the production of accurate force fields between Ln 3 + and the surrounding molecules.…”