SYMMETRICAL, UNSYMMETRICAL AND BRIDGED CALIX[4]ARENE DERIVATIVES AS NEUTRAL CARRIER IONOPHORES IN POLY (VINYL-CHLORIDE) MEMBRANE SODIUM-SELECTIVE ELECTRODES

The complexing ability of a range of 19 symmetrical, unsymmetrical and bridged calix[4]arene derivatives having ester, ketone, amide, amine and thioether functionalities were determined by the picrate extraction method. On incorporating these calix[4]arene derivatives as neutral carrier ionophores in sodium-selective poly (vinyl chloride) membrane electrodes the performance was assessed on the basis of the sensitivity and selectivity over the alkali, alkaline earth metals and hydrogen and ammonium ions. The temperature dependence, response times and lifetimes were also determined. Four ionophores in particular gave excellent sensitivity and selectivity and lifetimes of > 200 days. These electrodes were then tested without additional lipophilic additives and one ionophore was incorporated into poly (vinyl chloride) membrane electrodes with plasticizing solvents of varying polarity.