Analytical performance and stability studies of CoAu/rGO-based electrochemical sensor for arsenic(III) detection in aqueous solutions

Cobalt-gold nanoparticles (CoAu) were grafted on reduced graphene oxide (rGO) using a simple and scalable procedure. As-prepared CoAu/rGO nanocomposites were employed as electrode materials to detect trace amounts of arsenic(III) ions (As³⁺) in aqueous solutions using anodic stripping voltammetry. CoAu/rGO was thoroughly tested in the presence of As³⁺ in a neutral medium (bicarbonate buffer, pH = 7), and the limit of detection was found to be as low as 1.51 ppb, significantly lower than the maximum permissible value set by the World Health Organization at 10 ppb. Its possible sensor application was confirmed by the preserved response to As³⁺ ions in samples simultaneously containing interferents such as Cu²⁺ ions. The real-life application of this material was validated by the determination of As³⁺ ions in real samples from the city water supply system (the city of Zrenjanin in Vojvodina) and rivers (the Begej River, the Drina River and the Danube River). Besides the high sensitivity of CoAu/rGO towards As³⁺ ions, its stability was also monitored over a certain time, demonstrating that it can be used with great precision in sensors for routine water analysis over extended periods. Overall, this study offers a green, highly stable, accurate and precise electrochemical platform for arsenic detection that requires reagent-free sample preparation.