Core–Shell Molecularly Imprinted Polymer@SiO2@Fe3O4 for Low-Cost and Selective Electrochemical Sensing of Paraquat

Abstract

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)@SiO₂@Fe₃O₄ material with a portable screen-printed carbon electrode (SPCE). Adsorptive stripping voltammetry (AdSV) was employed to determine PQ using the proposed MIP@SiO₂@Fe₃O₄/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@SiO₂@Fe₃O₄/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.