Novel PVC-membrane potentiometric sensors based on a recently synthesized sulfur-containing macrocyclic diamide for Cd2+ ion. Application to flow-injection potentiometry

A new sulfur-containing macrocyclic diamide, 1,15-diaza-3,4,12,13-dibenzo-5,11-dithia-8-oxa-1,15-(2,6-pyrido)cyclooctadecan-2,14-dione, L, was synthesized, characterized and used as an active component for fabrication of PVC-based polymeric membrane (PME), coated graphite (CGE) and coated silver wire electrodes (CWE) for sensing Cd2+ ion. The electrodes exhibited linear Nernstian responses to Cd2+ ion in the concentration range of 3.3 × 10−6 to 3.3 × 10−1 M (for PME, LOD = 1.2 × 10−6 M), 2.0 × 10−7 to 3.3 × 10−1 M (for CWE, LOD = 1.3 × 10−7 M) and 1.6 × 10−8 to 1.3 × 10−1 M (for CGE, LOD = 1.0 × 10−8 M). The CGE was used as a proper detection system in flow-injection potentiometry (FIP) with a linear Nernstian range of 3.2 × 10−8 to 1.4 × 10−1 M (LOD = 1.3 × 10−8 M). The optimum pH range was 3.5-7.6. The electrodes revealed fairly good discriminating ability towards Cd2+ in comparison with a large number of alkali, alkaline earth, transition and heavy metal ions. The electrodes found to be chemically inert, showing a fast response time of <5 s, and could be used practically over a period of about 2-3 months. The practical utility of the proposed system has also been reported.