A Sodium Ion Selective Electrode Based on a Highly Lipophilic Monensin Derivative and Its Application to the Measurement of Sodium Ion Concentrations in Serum

Koji Tohda, Koji Suzuki, Nobutaka Kosuge, Hitoshi Nagashima, Kazuhiko Watanabe, Hidenari Inoue, Tsuneo Shirai

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15 Citations (Scopus)


Five kinds of monensin derivatives were synthesized by chemical modifications of the natural carboxylic polyether antibiotic monensin. Their usefulness as active compounds (Na+-ionophores) for Na+-selective poly(vinyl chloride)(PVC)-matrix membrane electrodes was examined. The electrodes based on monensin ester derivatives exhibited high Na+-selectivity. Among them, the electrode based on the highly lipophilic monensin dodecyl ester (log K° (partition constant)=8.7) had enough Na+-selectivity to determine the Na+-concentration in serum (log Kpot Na K=-1.1, log Kpot Na Mg==-4.0 and log Kpot Na Ca=-3.6); the electrode gave a Nernstian response (59.0 mV/pNa) ranging from 5×10-6 to 1 M Na+. The response potential of this electrode to a 0.1 MNa+ solution drifted within ±0.01 mV/h. The values of the Na+-concentration in artificial and real serum samples were successfully determined with the monensin dodecyl ester-based electrode using diisodecylphthalate as the electrode membrane solvent.

Original languageEnglish
Pages (from-to)227-232
Number of pages6
JournalAnalytical Sciences
Issue number2
Publication statusPublished - 1990



  • Ion selective electrode
  • lipophilicity
  • monensin derivative
  • serum
  • sodium ion

ASJC Scopus subject areas

  • Analytical Chemistry

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