Qin Yu, Peper Shane, Radu Aleksandar, Ceresa Alan, Bakker Eric
Department of Chemistry, Auburn University, Auburn, Alabama 36849, USA.
Anal Chem. 2003 Jul 1;75(13):3038-45. doi: 10.1021/ac0263059.
A derivative of a known Ca2+-selective ionophore, ETH 129, was synthesized to contain a polymerizable acrylic moiety (AU-1) and covalently grafted into a methyl methacrylate-co-decyl methacrylate polymer matrix. The polymer containing AU-1 was prepared via a simple one-step homogeneous polymerization method. It exhibited mechanical properties suitable for the fabrication of plasticizer-free ion-selective membrane electrodes and bulk optode films by solvent-casting and spin-coating techniques, respectively. The segmented sandwich membrane technique was utilized to assess the binding constant of free and covalently bound ionophores to calcium and to study their diffusion coefficients in the membrane phase. Diffusion was greatly diminished for the bound ionophore. This was confirmed in ion-selective electrode membranes containing no calcium ions in the inner solution, which should normally show apparent super-Nernstian response slopes in dilute calcium solutions. The response slope was Nernstian down to submicromolar concentration levels, indicating slow mass transport of calcium in the membrane. Optical-sensing films with the new copolymer matrix, unblended and blended with PVC-DOS, also confirmed that covalently bound ionophores are fully functional for maintaining selective ion extraction and binding properties of the sensing membrane.
合成了一种已知的Ca2+选择性离子载体ETH 129的衍生物，使其含有可聚合的丙烯酸部分（AU-1），并将其共价接枝到甲基丙烯酸甲酯-甲基丙烯酸癸酯聚合物基质中。含AU-1的聚合物通过简单的一步均相聚合方法制备。它分别通过溶剂浇铸和旋涂技术表现出适合制造无增塑剂离子选择膜电极和整体光极膜的机械性能。采用分段夹心膜技术评估游离和共价结合离子载体与钙的结合常数，并研究它们在膜相中的扩散系数。对于结合的离子载体，扩散大大减少。这在内溶液中不含钙离子的离子选择电极膜中得到证实，这种膜在稀钙溶液中通常应显示明显的超能斯特响应斜率。响应斜率在亚微摩尔浓度水平下符合能斯特方程，表明钙在膜中的传质缓慢。具有新型共聚物基质、未与PVC-DOS混合以及与PVC-DOS混合的光学传感膜也证实，共价结合的离子载体对于维持传感膜的选择性离子萃取和结合性能具有完全功能。
