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.