Sodium ion sensitive microelectrode based on a p-tert-butylcalix[4]arene ethyl ester

Planar sodium-selective potentiometric microelectrodes with a conducting polymer (polypyrrole doped with cobaltabis(dicarbollide) ions ([3,3′-Co(1,2-C2B9H11)2]−)) as solid contact layer between the polymeric sensitive membrane and the platinum substrate have been constructed. The p-tert-butylcalix[4]arene ethyl ester was used as ionophore for sodium recognition. The microelectrode shows a linear response for Na+ concentrations between 3.0 × 10−6 and 1.0 × 10−1 M with a Nernstian slope of 58.65 ± 2 mV per decade and a detection limit of 1.45 × 10−6 M. The response time was 14 s, and the electrode is suitable for use within the pH range of 3–10.