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 ([HClO₄]_Tot = 0.0316 and 0.0100 M). These data enabled to assess the speciation model and to determine the equilibrium constant of [Th(DFO)H₂]³⁺ at fixed ionic strength (I = 0.1 M (H,Na)ClO₄). 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)H₄⁺ and the chelate. The value of the apparent equilibrium constant (log β₁₁₂ = 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 Th⁴⁺ by the diprotonated ligand.

中文翻译：

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通过亲和毛细管电泳分配复杂的物种：Th（IV）-去铁草胺B的情况。

在两种酸度（[HClO ₄ ] _Tot = 0.0316和0.0100 M）下，通过增加背景电解质中th（IV）的浓度，通过UV吸收分光光度法监测去铁胺B（DFO）的电泳迁移率变化。这些数据能够评估物种模型并确定在固定离子强度（I = 0.1 M（H，Na）ClO _4的情况下[Th（DFO）H ₂ ] ³⁺的平衡常数。）。亲和毛细管电泳（ACE）通过确定其电荷和质子化状态对鉴定复杂的物种最有帮助。通过假设（DFO）H ₄ ⁺和螯合物具有相似的流体力学半径，正确的化学计量比的分配取决于对电泳迁移率的可靠估计。表观平衡常数的值（日志β ₁₁₂根据线性自由能关系，ACE获得的38.7±0.4）与th和一系列其他金属离子的文献中所报道的相当好。该方法对研究金属-配体结合平衡非常有用，并为进一步模拟四价act系元素在环境条件下的行为提供了有价值的信息。通过DFT计算获得了有关酸性条件下普遍存在的溶液物种的结构信息，这证实了双质子化配体对Th ⁴⁺的双氢xamato配位模式。