Departamento de Química Física, Facultad de Química, Regional Campus of International Excellence "Campus Mare Nostrum", Universidad de Murcia , 30100 Murcia, Spain.
Laboratorio de Electroquímica, Departamento de Química, Facultad de Ciencias, Universidad de los Andes , 5101 Mérida, Venezuela.
Anal Chem. 2018 Feb 6;90(3):2088-2094. doi: 10.1021/acs.analchem.7b04321. Epub 2018 Jan 16.
A new theory is presented to tackle the study of transfer processes of hydrophilic ions in two polarizable interface systems when the analyte is initially present in both aqueous phases. The treatment is applied to macrointerfaces (linear diffusion) and microholes (highly convergent diffusion), obtaining analytical equations for the current response in any voltammetric technique. The novel equations predict two signals in the current-potential curves that are symmetric when the compositions of the aqueous phases are identical while asymmetries appear otherwise. The theoretical results show good agreement with the experimental behavior of the "double transfer voltammograms" reported by Dryfe et al. in cyclic voltammetry (CV) ( Anal. Chem. 2014 , 86 , 435 - 442 ) as well as with cyclic square wave voltammetry (cSWV) experiments performed in the current work. The theoretical treatment is also extended to the situation where the target ion is lipophilic and initially present in the organic phase. The theory predicts an opposite effect of the lipophilicity of the ion on the shape of the voltammograms, which is validated experimentally via both CV and cSWV. For the above two cases, simple and manageable expressions and diagnosis criteria are derived for the qualitative and quantitative study of ion lipophilicity. The ion-transfer potentials can be easily quantified from the separation between the two signals making use of explicit analytical equations.
当分析物最初同时存在于两种水相时，提出了一种新理论来研究亲水性离子在两个可极化界面体系中的传递过程。该处理方法适用于宏观界面（线性扩散）和微孔（高度会聚扩散），为任何伏安技术中的电流响应获得了分析方程。新方程预测电流-电位曲线中有两个信号，当水相的组成相同时，这些信号是对称的，而在其他情况下则会出现不对称。理论结果与 Dryfe 等人在循环伏安法（CV）中报道的“双重转移伏安图”的实验行为（Anal. Chem. 2014, 86, 435-442）以及本工作中进行的循环方波伏安法（cSWV）实验吻合得很好。该理论处理还扩展到目标离子亲脂性且最初存在于有机相的情况。该理论预测离子亲脂性对伏安图形状的相反影响，这通过 CV 和 cSWV 实验得到了实验验证。对于上述两种情况，推导了简单且易于处理的表达式和诊断标准，用于离子亲脂性的定性和定量研究。可以从两个信号的分离中利用明确的分析方程轻松量化离子转移电位。
