Synthesis and Evaluation of a Bis(crown ether) Ionophore with a Conformationally Constrained Bridge in Ion-Selective Electrodes

• Published in: Analytical Sciences 1998, Vol.14(1), pp.169-173
• Main Authors: XIA, Zhiren, BADR, Ibrahim H. A., PLUMMER, Shawn L., CULLEN, Lawrence, BACHAS, Leonidas G.
• Format: Article
• Language: English
• ISSN: 0910-6340; 1348-2246
• DOI: 10.2116/analsci.14.169

A new bis(crown ether) ionophore containing two benzo-15-crown-5 moieties connected with each other via a conformationally constrained bridge attached to a C18-lipophilic side chain was designed and synthesized. The bridge consisted of an isophthalic acid derivative, which was selected in order to enhance potassium over sodium binding. Liquid-polymeric membrane ion-selective electrodes (ISEs) based on this ionophore were prepared using different plasticizers and mole ratios of lipophilic ionic additives. Membrane electrodes with optimum composition (using o-nitrophenyloctyl ether or bis(1-butylpentyl)adipate as plasticizer and 60 mol% lipophilic borate additive) show Nernstian responses toward potassium (57 and 58 mV/decade, respectively) over a wide concentration range with a micromolar detection limit. These ISEs exhibit enhanced potassium over sodium selectivity (KpotK+,Na+=6×10-4). In addition, the electrodes show selectivities for potassium over Cs+ and NH4+ that are better than those of valinomycin-based ISEs.