Salvador José, Garcés José Luis, Galceran Josep, Puy Jaume
Departament de Química, Universitat de Lleida, Rovira Roure 191, 25198, Lleida, Spain.
J Phys Chem B. 2006 Jul 13;110(27):13661-9. doi: 10.1021/jp061748s.
The rigorous analytical solution for the fluxes from a mixture of 1:1 metal complexes toward an active surface under steady-state planar diffusion in a finite domain and excess ligand conditions allows for the computation of the global degree of lability of the system as well as particular degrees of lability of each complex in the mixture. This kind of system is found in a variety of fields ranging from electrochemical techniques (such as stripping chronopotentiometry at scanned deposition potential, SSCP) to analytical devices (such as diffusion gradients in thin-film gels, DGT). Among the specific effects arising from the presence of a mixture of ligands competing for the metal we highlight the following: (i) The degree of lability of a complex in the mixture differs from its degree of lability in an unmixed system with the same ligand concentration, and (ii) the degree of lability of one complex depends on (i.e., can be modified with) the concentrations of the ligands in the mixture. The impact of these characteristics on the metal flux crossing the active surface reaches the highest value when both complexes are partially labile. The complex contribution to the metal flux goes through a maximum when the thickness of the diffusion domain is varied. Thus, the thickness of the diffusion domain can be chosen to enhance the contribution of one particular complex. Lability criteria for each complex of the mixture within the reaction layer approximation are also reported. In particular, the reaction layer formulation for a complex is discussed in detail for two limiting cases: the rest of complexes are all nonlabile or the rest of complexes are all labile.
在有限域和过量配体条件下，稳态平面扩散时从1:1金属配合物混合物向活性表面的通量的严格解析解，可用于计算系统的整体活性程度以及混合物中每种配合物的特定活性程度。这种系统存在于从电化学技术（如在扫描沉积电位下的溶出计时电位法，SSCP）到分析装置（如薄膜凝胶中的扩散梯度，DGT）等各种领域。在由竞争金属的配体混合物的存在而产生的特定效应中，我们突出以下几点：（i）混合物中一种配合物的活性程度与其在具有相同配体浓度的未混合系统中的活性程度不同，并且（ii）一种配合物的活性程度取决于（即可以用）混合物中配体的浓度来改变。当两种配合物都部分不稳定时，这些特性对穿过活性表面的金属通量的影响达到最大值。当扩散域的厚度变化时，配合物对金属通量的贡献经历一个最大值。因此，可以选择扩散域的厚度来增强一种特定配合物的贡献。还报道了在反应层近似内混合物中每种配合物的活性标准。特别是，针对两种极限情况详细讨论了一种配合物的反应层公式：其余配合物都不活泼或其余配合物都活泼。
