Development of High-Performance Ion Sensors Based on the Functions of Crown Ethers and Synthetic Bilayer Membranes

Hiroyuki YANAGI*, Toru SAKAKI and Takayuki OGATA††

Tokuyama Corporation Fujisawa Research Laboratory; 2023-1 Endo, Fujisawa-shi 252-0816 Japan
Present address: A & T Corporation Hino Techno-Site; 320-11, Hino, Hino-shi 191-0012 Japan
†† Present address: Tokuyama Corporation; 3-3-1 Shibuya, Shibuya-ku, Tokyo 150-8383 Japan

High-Performance Na+, K+ and Cl ion selective electrodes(ISEs) are reported. These are based on a new concept, which is an ion recognition site formed by molecular interaction. In the case of Na and K ISEs, crown ether compounds connecting with planar substituents were used as the ionophores. The selectivities depend on the structure of substituents. It is found that the intermolecular interaction of the planar substituent plays an important role on the improvement of selectivity. The selectivities of interactive mono(crown ether) are equal to that of bis(crown ether). It means that ion recognition site like a bis(crown ether) is formed by the interaction of mono(crown ehter)s. In the case of Cl ISE, immobilized synthetic bilayer membrane with quaternary ammonium salts was used as the ion sensitive membrane. In the immobilized synthetic bilayer membrane, ordered molecular aggregates is formed. It is found that the molecular orientation improved the Cl selectivity. The insufficient selectivity over lipophilic anions can be controlled by addition of aliphatic alcohol. These resulting ISEs exhibit high speed response and long life time, and they are applicable to clinical use which demands both accurate measurement and high speed processing.

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