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Assignment of complex species by affinity capillary electrophoresis: The case of Th(IV)‐desferrioxamine B
Author(s) -
Sladkov Vladimir,
Roques Jérôme,
Meyer Michel
Publication year - 2020
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/elps.202000114
Subject(s) - capillary electrophoresis , chemistry , ionic strength , electrophoresis , thorium , stoichiometry , protonation , metal , electrolyte , equilibrium constant , ligand (biochemistry) , stability constants of complexes , chelation , metal ions in aqueous solution , affinity electrophoresis , ionic bonding , ion , analytical chemistry (journal) , inorganic chemistry , chromatography , aqueous solution , affinity chromatography , materials science , biochemistry , receptor , uranium , organic chemistry , electrode , metallurgy , enzyme
Abstract The electrophoretic mobility change of desferrioxamine B (DFO) was monitored by UV absorption spectrophotometry upon increasing the thorium(IV) concentration in the background electrolyte at two acidities ([HClO 4 ] Tot = 0.0316 and 0.0100 M). These data enabled to assess the speciation model and to determine the equilibrium constant of [Th(DFO)H 2 ] 3+ at fixed ionic strength ( I = 0.1 M (H,Na)ClO 4 ). Affinity capillary electrophoresis (ACE) turned out to be most helpful in identifying the complexed species by ascertaining its charge and protonation state. The assignment of the correct stoichiometry relied on the reliable estimation of the electrophoretic mobility by assuming similar hydrodynamic radii for (DFO)H 4 + and the chelate. The value of the apparent equilibrium constant (log β 112 = 38.7 ± 0.4) obtained by ACE compares favorably well with those reported in the literature for thorium and a range of other metal ions, according to a linear free‐energy relationship. This method is useful for studying metal‐ligand binding equilibria and provides valuable information for further modelling the behavior of tetravalent actinides under environmental conditions. Structural information about the prevalent solution species in acidic conditions was gained by DFT calculations, confirming the bishydroxamato coordination mode of Th 4+ by the diprotonated ligand.