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

Abstract

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.