Electrochemical sensors for the determination of Zn2+ ions based on pendant armed macrocyclic ligand

The construction and performance characteristics of polymeric membrane electrodes based on two newly synthesized macrocyclic ligands 6,7:14,15-Bzo(2)-10,11-(4-methylbenzene)-[15]-6,8,12,14-tetraene-9, 12-N-2-1,5-O-2 (L-1) and 6,7: 14,15-Bzo(2)-10,11-(4-methylbenzene)-[15]-6,14-diene-9,12-dimethylacrylate-9,12-N-2-1,5-O-2 (L-2) for the quantification of Zn2+ ions are described here. Several membranes having different compositions of PVC, plasticizers, ionic additives and ionophores were fabricated and the best response was observed for the membrane having composition L-2:PVC:TBP:NaTPB in the ratio of 4:37:57:2 (w/w; mg). The response characteristics of the membrane based on L-2 were compared with polymeric membrane electrode (PME) as well as with coated graphite electrode (CGE). The electrode exhibits Nernstian slope for Zn2+ ions with limits of detection of 3.3 x 10(-7) mol L-1 for PME and 7.9 x 10(-8) mol L-1 for CGE with response time of 12s and 10s for PME and CGE respectively. Furthermore, the electrodes generated constant potentials in the pH range of 3.0-8.0 for PM E and 2.5-9.0 for CGE. The practical utility of the CGE has been demonstrated by its usage as an indicator electrode in potentiometric titration of EDTA with Zn2+ ion solution. The high selectivity of CGE also permits their use in the determination of Zn2+ ions in water, biological, milk and tea samples. (C) 2011 Elsevier Ltd. All rights reserved.