LEAD SELECTIVE ELECTRODES BASED ON THIOAMIDE FUNCTIONALIZED CALIX[4]ARENES AS IONOPHORES

Lead selective electrodes based on a di- and tetrathioamide functional ized calix[4] arene as ionophores were investigated. The Pb(II)-respon se functions exhibited almost theoretical Nernstian slopes in the acti vity range 10(-6)-10(-2) M of lead ions. For both ionophores a prefere nce for lead over other cations was observed. The best results were ob tained for membranes containing the tetrathioamide derivative (ionopho re 1), potassium tetrakis(4-chlorophenyl)borate and o-nitrophenyl octy l ether as a plasticizer. This electrode showed greatly improved selec tivity over copper, zinc and cadmium ions as compared with commercial solid-state lead selective electrodes.