LEAD(II)-SELECTIVE MEMBRANE ELECTRODES BASED ON ENOYL-1,10-DIOXA-4,7,13,16-TETRAAZACYCLOOCTADECANE

Lead(II)-selective PVC membrane electrodes based on enoyl-1,10-dioxa-4 ,7,13,16-tetraazacyclooctadecane (TTOTC) as ionophore were prepared. T he optimum composition of the membrane was 30 wt% poly(vinyl chloride) , 67 wt% 2-nitrophenyl octyl ether plasticizer, 3 wt% ionophore with a dded lipophilic salt potassium tetrakis(p-chlorophenyl)borate at 50 mo l% with respect to the ionophore concentration. The electrodes exhibit ed near theoretical Nernstian slopes (31.9 +/- 0.4 mV/per decade) in t he activity range log(10)[a(Pb2+)] = -5.3 to log(10)[a(Pb2+)] = -3.0 a nd with a detection limit log(10)[a(Pb2+)] = -5.7. Compared to the pre viously reported disubstituted, diazacrown enoyl-1,4,10,13-tetraoxa-7, 16-diazacyclooctadecane the electrodes based on TTOTC showed much bett er selectivity particularly towards alkali and alkaline metal ions. Ho wever, mercury and silver remain the major interferences. The electrod es were used in potentiometric titrations of Pb2+ and the determinatio n of Pb2+ in synthetic soil samples.