Simultaneous detection of cadmium and lead ions in grains using an electrochemical sensor based on a Co-ZIF@carbonized litchi pericarp composition

Abstract

Heavy metal ions in food pose severe health risks, necessitating the development of simple and effective detection methods. In this study, we constructed an electrochemical sensor for simultaneous detection of Cd²⁺ and Pb²⁺ by modifying a glassy carbon electrode (GCE) with a composite of a cobalt-based zeolitic imidazolate framework (Co-ZIF) and carbonized litchi pericarp (LP) for the first time. The Co-ZIF@LP/GCE sensor leverages a synergistic “adsorption–conduction” mechanism: Co-ZIF provides abundant adsorption sites and catalytic activity, while LP enhances electrical conductivity and stability. Electrochemical performance was evaluated using cyclic voltammetry and electrochemical impedance spectroscopy. Key parameters including buffer pH, modification material ratio, drop-coating volume, deposition potential, deposition time, and quiet time were optimized via square wave stripping voltammetry. Under optimal conditions, the sensor exhibited high sensitivity toward Cd²⁺ and Pb²⁺, with wide linear ranges (1–10 μM, 10–65 μM) and low detection limits (0.028 μM and 0.197 μM). Practical application in rice and millet samples demonstrated good recovery and precision, confirming the method's reliability for detecting heavy metal ions in food samples.