Highly sensitive voltammetric determination of Pb²⁺ and Cd²⁺ ions using a carbon paste electrode modified with Mn₀.₅Zn₀.₅Fe₂O₄ spinel ferrite nanoparticles

Abstract A novel electrochemical sensing platform based on a Mn 0.5 Zn 0.5 Fe 2 O 4 nanoparticles-modified carbon paste electrode (MnZnFe NPs/CPE) was developed for the simultaneous voltammetric determination of trace Cd² + and Pb² + ions. MnZnFe NPs were synthesized via co-precipitation method and characterized by FTIR, XRD, SEM&EDX, and TEM analyses, confirming the formation of a well-crystallized spinel ferrite structure with nanoscale morphology. The incorporation of MnZnFe NPs significantly enhanced the electrocatalytic activity of the carbon paste matrix, providing improved adsorption capacity and electron-transfer kinetics for metal ions. Adsorptive stripping differential pulse voltammetry (ASDPV) was employed for analytical measurements under optimized conditions (pH 5, deposition potential − 1.2 V, deposition time 120 s). The modified electrode exhibited well-defined and separated oxidation peaks for both Cd² + and Pb² + , achieving low detection limits 0.21 nM and 0.03 nM for Cd² + and Pb² + respectively, wide linear ranges 0.80 nM – 28.0 µM and 0.12 nM– 30.0 µM for Cd² + and Pb² + respectively, and excellent reproducibility (RSDs of 0.42% (Cd² + ) and 1.39% (Pb² + )). The sensor also demonstrated high selectivity toward Cd²⁺ and Pb²⁺, with negligible interference from common coexisting ions, and showed good stability over repeated use. The developed MnZnFe NPs/CPE provides a simple, low-cost, and efficient approach for monitoring toxic heavy metals in environmental water samples.