Melamine-Derived Molecularly Imprinted Polymer on a Low-Cost Pencil Graphite Electrode Electrochemical Sensor for Sensitive Thiamethoxam Detection

A novel electrochemical sensor was developed for the sensitive and selective detection of thiamethoxam, leveraging melamine’s multi-orientation polymerization via in situ electropolymerization on a pencil graphite electrode. The molecularly imprinted polymer membrane was electrochemically deposited using cyclic voltammetry, with thiamethoxam as the template to create specific binding sites. After template removal, the molecularly imprinted polymer-modified pencil graphite electrode was characterized by scanning electron microscopy and cyclic voltammetry, confirming the successful formation of a porous imprinted layer with enhanced electron transfer resistance. The DPV signal decline, attributed to the competitive binding of thiamethoxam at the MIP sites, showed a linear relationship with thiamethoxam concentrations over a wide range (100 nM–200 μM), with a low limit of detection (100 nM). The sensor exhibited excellent selectivity toward thiamethoxam, with minimal interference from structural analogs and environmental ions. Spiked recovery resultants in water and food samples was obtained as 98.398%–102.306% and relative standard deviations below 15%, demonstrating reliable accuracy for real-world applications. The proposed electrochemical sensor offered a low-cost, easy-to-fabricate platform for thiamethoxam detection with high sensitivity.