Selective and simultaneous detection of cadmium, lead and copper by tapioca-derived carbon dot-modified electrode

The need for the sensing of environmental pollutants cannot be overemphasized in the twenty-first century. Herein, a sensor has been developed for the sensitive and selective detection of copper (Cu²⁺), lead (Pb²⁺) and cadmium (Cd²⁺) as major heavy metals polluting water environment. A screen-printed carbon electrode (SPCE) modified by fluorescent carbon dots (CDs) and gold nanoparticles (AuNPs) was successfully fabricated for sensing Cu²⁺, Pb²⁺ and Cd²⁺. Differential pulse voltammetry (DPV) and cyclic voltammetry (CV) were deployed for the analysis of ternary analytes. CV was set at a potential range of - 0.8 to + 0.2 V at a scan rate of 100 mV/s, and DPV at a potential range of - 0.8 to + 0.1 V, scan rate of 50 mV/s, pulse rate of 0.2 V and pulse width of 50 ms. DPV technique was applied through the modified electrode for sensitive and selective determination of Cu²⁺, Pb²⁺ and Cd²⁺ at a concentration range of 0.01 to 0.27 ppm for Cu²⁺, Pb²⁺ and Cd²⁺. Tolerance for the highest possible concentration of foreign substances such as Mg²⁺, K⁺, Na⁺, NO₃^-, and SO₄^2- was observed with a relative error less than ± 3%. The sensitivity of the modified electrode was at 0.17, 0.42 and 0.18 ppm for Cd²⁺, Pb²⁺ and Cu²⁺, respectively, while the limits of detection (LOD) achieved for cadmium, lead and copper were 0.0028, 0.0042 and 0.014 ppm, respectively. The quality of the modified electrode for sensing Cu²⁺, Pb²⁺ and Cd²⁺ at trace levels is in accordance with the World Health Organization (WHO) and Environmental Protection Agency (EPA) water regulation standard. The modified SPCE provides a cost-effective, dependable and stable means of detecting heavy metal ions (Cu²⁺, Pb²⁺ and Cd²⁺) in an aqueous solution. Graphical abstract .