Selective electrochemical determination of trace level copper using a salicylaldehyde azine/MWCNTs/Nafion modified pyrolytic graphite electrode by the anodic stripping voltammetric method

A novel Cu2+ electrochemical sensor based on a salicylaldehyde azine/MWCNTs/Nafion-modified pyrolytic graphite electrode was prepared for anodic stripping analysis of Cu2+. Salicylaldehyde azine was synthesized and then used for the selective determination of the heavy metal pollutant Cu2+ due to its azine structure, which gave selective complexing ability toward Cu2+. The use of MWCNTs with their strong adsorption ability could greatly enhance the sensitivity. Nafion, a proton-exchange polymer, was used as the conductive matrix in which the salicylaldehyde azine and MWCNTs could be strongly fixed to the substrate electrode surface. The as-prepared electrochemical sensor showed remarkably enhanced selectivity and sensitivity towards Cu2+. The response current of the sensor was linear with Cu2+ concentration ranging from 5 to 300 nM under 15 min accumulation at open-circuit potential, with a very low detection limitation of about 1 nM. The hybrid functionalized electrode also exhibited good selectivity to avoid the interference of other heavy metal ions like Cd2+, Pb2+ and Hg2+ in the mixture solution together with Cu2+. Real application towards environmental sample analysis confirmed that the modified electrode could be applied for the selective determination of trace levels of Cu2+ in the Yellow River.