Core–Shell Molecularly Imprinted Polymer@SiO 2 @Fe 3 O 4 for Low‐Cost and Selective Electrochemical Sensing of Paraquat

The widespread use of the water‐soluble paraquat (PQ) herbicide has found to be linked with numerous toxic outcomes to humans as well as aquatic animals, while the on‐site and rapid measurement is still challenging due to unsuitability and lack of selectivity of the existing techniques. This study presents a selective, sensitive, and low‐cost electrochemical sensor for detecting residual PQ in water by combining a core–shell molecularly imprinted polymer (MIP)@SiO 2 @Fe 3 O 4 material with a portable screen‐printed carbon electrode (SPCE). Adsorptive stripping voltammetry (AdSV) was employed to determine PQ using the proposed MIP@SiO 2 @Fe 3 O 4 /SPCE, exhibiting high analytical performance with a sensitivity of 7.27 µA/µM, a two‐segment linear range of 0.25–20 and 20–50 µM, and a detection limit of 0.043 µM. In addition, excellent selectivity towards PQ was achieved, even in the presence of a 20‐fold excess of interfering substances commonly found in various water matrices. Recoveries of 89.72%–113.46% were obtained at the MIP@SiO 2 @Fe 3 O 4 /SPCE for the determination of PQ in tap water, river water, and seawater samples, and the results were validated using high‐performance liquid chromatography, demonstrating its strong potential for practical applications in aquatic analysis.