Highly selective detection of heavy metal ions in food and water using a 5-BHAHS@NC/MnO2-based electrochemical sensor

Abstract

Human health and food safety face significant risks due to heavy metal contamination in food and water, as these metals can be accumulated to exhibit high toxicity even at low concentrations. Thus, electrochemical sensors, specifically voltammetry, provide a promising approach for simultaneous detection of heavy metal ions. In this study, a voltammetric assay was developed by directly immobilizing a newly synthesized ionophore structure, (E)-4-((5-bromo-2-hydroxybenzylidene) amino)-3-hydroxynaphthalene-1-sulfonic acid) (5-BHAHS), onto nano-cellulose (NC) synthesized via green methods, along with MnO₂ nanoparticles. The sensing material and its parent nano-cellulose base were characterized using HR-TEM, FT-IR, FE-SEM, XPS, and XRD. Subsequently, various factors influencing metal ion detection were studied and optimized, resulting in detection limits of 0.12 µM for both Hg²⁺ and Cd²⁺, and 0.03 µM for Pb²⁺. Optimal conditions for accumulation time, electrolyte pH, scan rate, selectivity, and sensitivity were determined to achieve rapid simultaneous detection at low concentrations. The 5-BHAHS@NC/MnO₂-based sensor proved to be a robust tool for the simultaneous detecting Hg²⁺, Cd²⁺, and Pb²⁺ ions in tap water, wastewater, and fish samples demonstrating high selectivity. Notably, the sensitivity achieved by the 5-BHAHS@NC/MnO₂ sensor is higher than that reported in previous studies, highlighting its superior performance, non-toxicity feedback and potential for practical applications in food safety and environmental monitoring.