Baniwal S, Chandra S, Panwar A, Singh A K
Department of Chemistry, University of Roorkee, Roorkee, 247667 U.P., India.
Talanta. 1999 Oct;50(3):499-508. doi: 10.1016/s0039-9140(99)00156-3.
Poly(vinyl chloride)-based membranes of macrocycles 4,11-dimethyl-2,4,9,11-tetraethyl-1,5,8,12-tetraaza cyclotetradeca-1,8-diene (I) and 4,11-dioxa-2,9-dimethyl-1,5,8,12-tetraaza cyclotetradeca-1,8-diene (II) with sodium tetraphenyl borate (STB) as an anion excluder and dibutyl phthalate (DBP), dioctyl phthalate (DOP), dibutylbutyl phosphonate (DBBP) and 1-chloronaphthalene (CN) as plasticizing solvent mediators were prepared and investigated as magnesium selective electrodes. The best performance was observed having the composition (II)-PVC-STB-DBP in the ratio 2:10:1:7, which works well over a wide concentration range (1.9x10(-6) to 1.0x10(-1) M) with a Nernstian slope of 29 mV per decade of activity between pH 2.5 and 6.5. These electrodes have been found to be chemically inert showing a fast response time of 15 s and were used over a period of 3 months with good reproducibility (S=+/-0.2 mV). The selectivity coefficient values for mono-, di- and trivalent cations indicate excellent selectivity for Mg(2+) over a large number of cations. The electrodes have also been used successfully in partially non-aqueous medium and as an indicator electrode in the potentiometric titration of Mg(2+) with EDTA. Anions such as Cl(-) and SO(4)(2-) do not interfere in the working of the electrode. The practical utility of the membrane sensor has also been observed in solutions contaminated with detergents (cetyltrimethyl ammonium bromide and sodium dodecyl sulphate). Above all, the membrane sensor has been very successfully used to analyse some babyfood products and soft drinks for the determination of Mg(2+).
以大环化合物4,11 - 二甲基 - 2,4,9,11 - 四乙基 - 1,5,8,12 - 四氮杂环十四碳 - 1,8 - 二烯（I）和4,11 - 二氧杂 - 2,9 - 二甲基 - 1,5,8,12 - 四氮杂环十四碳 - 1,8 - 二烯（II）为基础的聚氯乙烯膜，以四苯硼钠（STB）作为阴离子排除剂，邻苯二甲酸二丁酯（DBP）、邻苯二甲酸二辛酯（DOP）、丁基膦酸二丁酯（DBBP）和1 - 氯萘（CN）作为增塑溶剂介质，制备并研究了它们作为镁离子选择性电极的性能。观察到组成比例为（II） - PVC - STB - DBP（2:10:1:7）时性能最佳，该电极在较宽的浓度范围（1.9×10⁻⁶至1.0×10⁻¹ M）内表现良好，在pH 2.5至6.5之间，能斯特斜率为每十倍活度变化29 mV。这些电极具有化学惰性，响应时间快，为15秒，在3个月的使用期内具有良好的重现性（S = ±0.2 mV）。对单价、二价和三价阳离子的选择性系数值表明，该电极对Mg²⁺相对于大量阳离子具有优异的选择性。该电极还成功应用于部分非水介质中，以及在以EDTA电位滴定Mg²⁺时作为指示电极。诸如Cl⁻和SO₄²⁻等阴离子不干扰电极的工作。在含有洗涤剂（十六烷基三甲基溴化铵和十二烷基硫酸钠）的溶液中也观察到了该膜传感器的实际应用价值。最重要的是，该膜传感器已非常成功地用于分析一些婴儿食品和软饮料中的Mg²⁺含量。
