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基于扩散层模型解释了固态电极的选择性系数。依据Nernst方程,主要离子的浓度可用扩散系数D_B、D_C与AB+C AC+B反应平衡常数的关系来表示。这里AB代表膜材料,C代表干扰离子,方程式的形式为: 此处用下标“0”标志的浓度是表示直接感应电极电位的表面浓度,而[B]和[C]是所指物质的容积浓度。以这个模型为基础能够说明各种文献数据之间的差异。 在离子选择电极发展方面,基础研究的作用正在不断增长。着重于各种现象,对电极机能已经提出了几种模型。近来,对膜表面的扩散过程给予了很大的注意,而撇开了更难研究的膜内过程。在溶液组分和膜材料之间络合物形成反应的基础上,在有关电极灵敏度的论述中,扩散现象的详细描述可能是有用的。 关于混合相的情况,R.P.巴克曾经描述了共存的两种固相与溶液中离子的热力学平衡,但仅有J.哈瓦斯(Havas)作了扩散过程的定量叙述。在早先的文章中,我们曾就铜离子选择电极(硫化铜)对此进行了定量讨论,但因在很低浓度水平时工作上的困难,这个实例的严格实验验证是困难的。 本文中这一方法已发展为更普遍的形式。这个论述使若干电极选择性系数的理论解释有了可能。这些数值可与混合溶液法和分别溶液法实验测定值相比较,在某些情况下还能解释存在的差异。
The selectivity coefficient of the solid state electrode is explained based on the diffusion layer model. According to the Nernst equation, the concentration of the major ions can be expressed by the relationship between the diffusion constant D_B, D_C and the equilibrium constant of AB + C AC + B reaction. Where AB is the membrane material and C is the interfering ion. The equation is of the form: where the concentration indicated by the subscript “0” is the surface concentration of the direct sensing electrode potential and [B] and [C] Volume concentration. Based on this model, we can explain the differences between various literature data. The role of basic research is growing in the development of ion-selective electrodes. Focusing on various phenomena, several models have been proposed for the electrode function. Recently, much attention has been paid to the diffusion of the membrane surface, leaving aside the more intra-membrane processes that are more difficult to study. On the basis of the complex formation reaction between the solution components and the membrane material, a detailed description of the phenomenon of diffusion may be useful in the discussion of electrode sensitivity. In the case of mixed phases, R.P. Buck has described the thermodynamic equilibrium of two coexisting solid phases with ions in solution, but only the quantitative description of diffusion processes by J. Havas. In a previous article we had a quantitative discussion of copper ion selective electrodes (copper sulfide), but rigorous experimental validation of this example was difficult due to operational difficulties at very low concentration levels. This method has evolved into a more general form in this article. This statement makes possible the theoretical explanation of several electrode selectivity coefficients. These values can be compared with the mixed solution and the solution method experimentally measured values, in some cases can explain the differences exist.