Single-step electrochemical sensing of ppt-level lead in leaf vegetables based on peroxidase-mimicking metal-organic...

A simple and sensitive electrochemical sensor was established for monitoring parts-per-trillion (ppt)-level lead in leaf vegetables based on Pb²⁺-dependent DNAzyme and porphyrin-functionalized metal-organic framework (porph@MOF). Especially, the prepared porph@MOF showed excellent peroxidase-mimicking activities and also exhibited high stability in a wide range of temperature and pH. Using porph@MOF as mimic catalyst for sensing construction, the limit of detection for Pb²⁺ analysis was found to be 5 pM (corresponding to 1 ppt by weight), which was quite qualified for the regular monitoring of lead pollution in leaf vegetables. Moreover, the proposed principle facilitated the anti-jamming assay due to the specific recognition behavior of DNAzyme to Pb²⁺, and could be applied to detect Pb²⁺ in presence of the interfering metal ions. When compared with multiple-operation approaches, this sensor was constructed with single-step protocol, thereby greatly simplifying the analytical process and enhancing the temporal efficiency. With these merits of simplicity, rapid response, high sensitivity and specificity, the electrochemical sensor offered a promising means for evaluating the safety of leaf vegetables polluted with lead.