No abstract

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 Nat-selective poly(vinyl chloride)(PVC)-matrix membrane electrodes was examined. The electrodes based on monensin ester derivatives exhibited high Nat-selectivity. Among them, the electrode based on the highly Lipophilic monensin dodecyl ester (log K° (partition constant)=8.7) had enough Nat-selectivity to determine the Nat-concentration in serum (log KNaK=-1.1, log Kv°aMg-4.0 and log KNaca-3.6); the electrode gave a Nernstian response (59.0 mV/pNa) ranging from 5X10-6 to 1 M Nat. The response potential of this electrode to a 0.1 M Na+ solution drifted within ±0.01 mV/ h. The values of the Nat-concentration in artificial and real serum samples were successfully determined with the monensin dodecyl ester-based electrode using diisodecylphthalate as the electrode membrane solvent.