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 extractio n 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 sensitivit y and selectivity over the alkali, alkaline earth metals and hydrogen and ammonium ions. The temperature dependence, response times and life times were also determined. Four ionophores in particular gave excelle nt sensitivity and selectivity and lifetimes of > 200 days. These elec trodes were then tested without additional lipophilic additives and on e ionophore was incorporated into poly (vinyl chloride) membrane elect rodes with plasticizing solvents of varying polarity.