Synthesis and Evaluation of a Bis(crown ether)Ionophore with a Conformationally Constrained Bridge in Ion-Selective Electrodes
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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.
- Analytical Sciences
Analytical Sciences 14(1), 169-174, 1998-02-10
The Japan Society for Analytical Chemistry