Potassium ion-selective optodes based on the calix[6]arene hexaester and application in human serum assay

Abstract

Plasticized PVC membranes incorporating the hexaester of calix[6]arene, potassium tetrakis(4-chlorophenyl) borate and a neutral H⁺-selective chromo-ionophore (ETH 5294) have been used as reversible sensing devices for optical determination of potassium ion in pH-buffer solutions. At pH 9.0, the absorbance response of the optode shows a good correlation with the theoretically derived formula in the range from 1 × 10^–6 to 1 × 10^–2 mol l^–1 potassium ion. Typical response times (t₉₅) in the samples are 3 min, the relative standard deviation for repeated measurements being within 0.5%. The selectivity of this potassium-selective membrane allows its application for the reversible optical detection of potassium concentration in human serum samples.