Green chelating IDS-Fe₃O₄ composite sensor for trace simultaneous detection of Cd²⁺, Pb²⁺, and Hg²⁺ in water samples

Heavy metal ions such as Cd²⁺, Pb²⁺, and Hg²⁺ pose significant environmental and public health concerns due to their toxicity and persistence. In this study, a sensitive electrochemical sensor based on a tetrasodium iminodisuccinate/SiO₂-coated Fe₃O₄-modified carbon paste electrode (IDS-Fe₃O₄@SiO₂/CPE) was developed for the simultaneous determination of these metal ions using differential pulse voltammetry. The synergistic integration of SiO₂-coated Fe₃O₄ nanoparticles with IDS enhanced the electrochemical performance of the sensor by improving electron-transfer kinetics, increasing the electroactive surface area, and providing effective surface-active sites for metal-ions accumulation. Under optimized conditions (pH 1.0, 0.1 M HNO₃/NaNO₃, and 10 mg modifier), the proposed sensor exhibited dual linear ranges of 0.03-0.9 and 3.0-100 μM for Cd²⁺, 0.01-1.0 and 5.0-100 μM for Pb²⁺, and 0.004-0.9 and 3.0-90 μM for Hg²⁺, with limits of detection of 0.0097, 0.0034, and 0.0012 μM, respectively. The sensor demonstrated satisfactory analytical performance, good repeatability, and operational stability over 21 days (RSD = 3.81%). Although noticeable interference was observed for Cu²⁺, CH₃COO^-, and NH₄⁺, reliable quantitative determination of Cd²⁺, Pb²⁺, and Hg²⁺ in real environmental water samples was successfully achieved using the standard addition method, providing recoveries between 94% and 110%. Owing to its simplicity, low cost, environmental compatibility, and competitive analytical performance, the proposed sensor represents a promising platform for trace-level monitoring of heavy metal contaminants in aquatic environments.