Qin Yu, Bakker Eric
Department of Chemistry, Auburn University, Auburn, Alabama 36849, USA.
Anal Chem. 2003 Nov 1;75(21):6002-10. doi: 10.1021/ac034447c.
The traditional cation exchangers used in ion-selective electrodes and optodes are tetraphenylborate derivatives, which are generally adequate for most analytical applications but may in some cases suffer from decomposition by acid hydrolysis, oxidants, and light. Recently, halogenated dodecacarboranes were found to be improved cation exchangers in terms of lipophilicity and chemical stability. This forms the basis for the convenient covalent attachment of the cation exchanger to the polymeric backbone of the sensing material. This is a challenge that has not satisfactorily been solved and which is especially important in view of developing ultraminiaturized sensing arrays. Here, a C-derivative of the closo-dodecacarborane anion (CB(11)H(12)(-)) with a polymerizable group was synthesized as a chemically stable cation exchanger. This new derivative was copolymerized with methyl methacrylate and decyl methacrylate (MMA-DMA) to fabricate a plasticizer-free polymer with cation-exchange properties. This polymer could be conveniently blended with traditional plasticized poly(vinyl chloride) or with noncrosslinked methacrylic polymers to give solvent cast films that appear to be clear and homogeneous and that could be doped with ionophores. Optode leaching experiments supported the covalent grafting of the carborane anions. Ion-selective membranes and optode thin films were evaluated in terms of response function, response time, and selectivity. In all cases, the new material exhibited behavior similar to free tetraphenylborate derivative-based membranes. As a result of these studies, an all-polymeric plasticizer-free calcium-selective membrane was fabricated on the basis of the covalently attached carborane, a recently introduced grafted calcium ionophore, and an MMA-DMA polymer matrix. The resulting ion-selective electrodes showed Nernstian response slopes and rapid response times, demonstrating that covalent grafting of all sensing components is a feasible approach to the development of ion sensors.
离子选择性电极和光极中使用的传统阳离子交换剂是四苯基硼酸盐衍生物，它们通常适用于大多数分析应用，但在某些情况下可能会因酸水解、氧化剂和光照而分解。最近，发现卤化十二碳硼烷在亲脂性和化学稳定性方面是改进的阳离子交换剂。这为阳离子交换剂方便地共价连接到传感材料的聚合物主链上奠定了基础。这是一个尚未得到满意解决的挑战，鉴于开发超小型传感阵列，这一挑战尤为重要。在此，合成了一种具有可聚合基团的闭式十二碳硼烷阴离子（CB(11)H(12)(-)）的C衍生物作为化学稳定的阳离子交换剂。这种新衍生物与甲基丙烯酸甲酯和癸基丙烯酸甲酯（MMA-DMA）共聚，以制备具有阳离子交换性能的无增塑剂聚合物。这种聚合物可以方便地与传统的增塑聚氯乙烯或非交联甲基丙烯酸聚合物混合，得到外观清晰均匀且可掺杂离子载体的溶剂浇铸膜。光极浸出实验支持了碳硼烷阴离子的共价接枝。根据响应函数、响应时间和选择性对离子选择性膜和光极薄膜进行了评估。在所有情况下，新材料表现出与基于游离四苯基硼酸盐衍生物的膜类似的行为。这些研究的结果是，基于共价连接的碳硼烷、最近引入的接枝钙离子载体和MMA-DMA聚合物基质，制备了一种全聚合物无增塑剂钙选择性膜。所得的离子选择性电极显示出能斯特响应斜率和快速响应时间，表明所有传感组件的共价接枝是开发离子传感器的一种可行方法。
