Ratiometric Electrochemical Aptasensor with Magnetic Separation-Assisted Entropy Driven Catalyst for Dual Detection of Pb²⁺ and Hg²⁺ in Aquatic Products: A High-Amplification Strategy for Food Safety Monitoring

The simultaneous presence of heavy metal ions (HMIs) such as Pb²⁺ and Hg²⁺ pose severe risks to food safety, particularly in aquatic products. Herein, a ratiometric electrochemical aptasensor integrated with magnetic separation-assisted entropy driven catalyst (EDC) was developed for simultaneous detection of Pb²⁺ and Hg²⁺. In this work, Fe@ZIF67-NH₂, an iron-doped zeolitic imidazolate framework, as both an electrode modifier and an internal reference, providing stable electrochemical signals and enhanced surface area. Herein, we utilized Fe@ZIF67-NH₂ (an iron-doped zeolitic imidazolate framework) as both an electrode modifier and an internal reference to provide stable electrochemical signals and increase the surface area. Dual EDC reactions amplified Pb²⁺ and Hg²⁺ signals independently, while magnetic separation isolated carbon dots (CDs) labelled DNA strands (CDP-D1 and CDH-P1) from interference strands, minimizing background noise. The sensor demonstrated wide linear ranges of 0.2-2.0×10⁴ ng mL⁻ 1 for Pb²⁺ and 0.1-1.0×10⁴ ng mL⁻ 1 for Hg²⁺, with detection limits of 0.1   ng   mL⁻ 1 and 0.03   ng   mL⁻ 1 , respectively. Practical validation using dried seafood samples showed recovery rates of 96.4-107.0% and relative standard deviations (RSDs) < 6.60%, and were consistent with inductively coupled plasma mass spectrometry (ICP-MS). This work presents a highly amplification-efficient and sensitive strategy for multiplex HMI detection in complex matrices, offering significant potential for food safety monitoring and environmental analysis.