Düssel H, Dostal A, Scholz F
Institut für Chemie, Humboldt Universität zu Berlin, Hessische Strasse 1-2, D-10115, Berlin, Germany.
Anal Bioanal Chem. 1996 Apr;355(1):21-8. doi: 10.1007/s0021663550021.
Composite electrodes made of graphite, paraffin and metal hexacyanoferrates exhibit a voltammetric response of the hexacyanoferrate ions, the potential of which depends linearly on the logarithm of concentration of alkali and alkaline-earth metal ions. This behaviour has been observed on account of the fact that the electrochemical reaction is accompanied by an exchange of these ions between the solution and the zeolitic lattice of the hexacyanoferrates for charge compensation. The voltammetric determination of the formal potential of these electrodes in a solution allows the quantitative analysis of the ions which are exchanged between the metal hexacyanoferrates and the aqueous solutions. Iron(III), copper(II), silver(I), nickel(II) and cadmium(II) hexacyanoferrates have been studied for the determination of H(+), Li(+), Na(+), K(+), Rb(+), Cs(+), NH(+)(4), Mg(2+), Ca(2+) and Ba(2+). In some cases, the selectivity constants are as low as 3.10(-4), or even so small that their exact value is inaccessible. Electrodes made of iron (III), copper (II), silver (I), nickel (II) and cadmium (II) hexacyanoferrates are most suitable for the determination of potassium ions. Electrodes with nickel (II) and cadmium (II) hexacyanoferrates are also suitable for the determination of caesium ions. The working range of the electrodes also depends on the conductivity of the solutions and can range from 10(-5) to 1 mol l(-1). Typical standard deviations of the potential measurements are 3 mV.
由石墨、石蜡和金属六氰合铁酸盐制成的复合电极呈现出六氰合铁酸根离子的伏安响应，其电位与碱金属和碱土金属离子浓度的对数呈线性关系。观察到这种行为是因为电化学反应伴随着这些离子在溶液和六氰合铁酸盐的沸石晶格之间的交换以进行电荷补偿。在溶液中对这些电极的形式电位进行伏安测定，可以对在金属六氰合铁酸盐和水溶液之间交换的离子进行定量分析。已经研究了铁（III）、铜（II）、银（I）、镍（II）和镉（II）的六氰合铁酸盐用于测定H(+)、Li(+)、Na(+)、K(+)、Rb(+)、Cs(+)、NH(+)(4)、Mg(2+)、Ca(2+)和Ba(2+)。在某些情况下，选择性常数低至3×10(-4)，甚至小到无法获得其确切值。由铁（III）、铜（II）、银（I）、镍（II）和镉（II）的六氰合铁酸盐制成的电极最适合测定钾离子。含有镍（II）和镉（II）六氰合铁酸盐的电极也适用于测定铯离子。电极的工作范围还取决于溶液的电导率，范围可以从10(-5)到1 mol l(-1)。电位测量的典型标准偏差为3 mV。
