Advantages and Limitations of Reference Electrodes with an Ionic Liquid Junction and Three-Dimensionally Ordered Macroporous Carbon as Solid Contact
Advantages and Limitations of Reference Electrodes with an Ionic Liquid Junction and Three-Dimensionally Ordered Macroporous Carbon as Solid Contact
复制标题
DOI：
10.1021/ac3011507
复制
发表时间：
2012-09-18
影响因子：
7.4
通讯作者：
Buehlmann, Philippe
中科院分区：
文献类型：
--
作者：
Zhang, Tiantian;Lai, Chun-Ze;Buehlmann, Philippe
通过离子液体掺杂的疏水聚合物膜与样品接触的无液结参比电极引起了人们的关注，因为它们提供了一种替代传统盐桥参比电极的方法。本工作利用离子液体(IL)1-甲基-3-辛基咪唑双(三氟甲磺酰亚胺)掺杂的增塑聚氯乙烯膜制备了无液结的参比电极。用注入了该离子液体相的三维有序大孔(3DOM)碳基片作为这些参照膜的固体接触。与之前使用基于离子载体的3DOM碳接触离子选择电极的工作一样，无液结参比电极的长期稳定性很好，在26天内电位漂移低至42微伏/小时。成功地测量了牛奶中的pH值，据我们所知，这是第一个在复杂的现实生活样品中使用无液结参比电极的例子。对它们在低pH下的性能进行了深入的分析，发现离子液体阴离子(L-)发生质子化，并在参比电极膜中形成LHL型缔合物，这是以前工作中没有观察到的效果。此外，当将参照膜安装到具有不含离子液体离子的内部填充溶液的传统电极体内时，样品/膜界面上的零电流离子通量发生，正如以前仅在离子载体掺杂的离子选择膜中看到的那样。了解这些效应对于设计适用于其他应用的无液结参比电极至关重要。
Liquid-junction-free reference electrodes that contact the sample through an ionic-liquid-doped, hydrophobic polymer membrane have attracted attention because they offer an alternative to reference electrodes with conventional salt bridges. In this work, liquid-junction-free reference electrodes were developed using plasticized poly(vinyl chloride) membranes doped with the ionic liquid (IL) 1-methyl-3-octylimidazolium bis(trifluoromethylsulfonyl)-imide. Three-dimensionally ordered macroporous (3DOM) carbon substrates infused with this ionic liquid phase were used as solid contacts for these reference membranes. As in prior work with ionophore-based 3DOM carbon-contact ion-selective electrodes, the long-term stability of the liquid-junction-free reference electrodes was excellent, with potential drifts as low as 42 mu V/h over 26 days. Successful measurements of pH in milk were performed and, to the best of our knowledge, are the first example of the use of liquid-junction-free reference electrodes in complex real-life samples. A thorough analysis of their performance at low pH revealed protonation of the ionic liquid anion (L-) and formation of LHL- type of associates in the reference electrode membrane, effects not observed in prior work. Also, when reference membranes were mounted into conventional electrode bodies with inner filling solutions that contained no ionic liquid ions, zero-current ion fluxes across the sample/membrane interface occurred, as previously only seen for ionophore-doped ion-selective membranes. Understanding these effects will be crucial to the design of liquid-junction-free reference electrodes suitable for other applications.