Potassium ion-selective membrane electrodes based on 1,3-alternate calix[4] crown-5-azacrown-5

A series of 1,3-alternate calix[4]azacrown ethers for which the monoaza and unsymmetrical crowned-azacrown with different side arms were examined as an ionophore for ion-selective polymeric membrane electrode toward potassium ion. Among them, the electrode based on calix[4] crown-5-azacrown-5 with a phenyl group exhibited near Nernstian response for K⁺ ions over a wide concentration range (1 × 10^-5 to 1 × 10^-1 M) with a limit of detection of 2 × 10^-6 M. It has a fast response time of approximately 2-3 s and can be used for at least 2 months without observing any major deterioration. Selectivity coefficients indicated that interference from all common alkali, alkaline and transition metal ions was very small.