Enhanced Electrochemical Detection of Nitrite Using Prussian Blue‐Coated Fe 3 O 4 Magnetic Nanoparticles as Peroxidase Mimetics

Herein, Fe 3 O 4 magnetic nanoparticles (Fe 3 O 4 MNPs) were synthesized via a one‐step counter‐coprecipitation method, and Prussian blue (PB) nanoparticles were subsequently modified in situ on the surface of Fe 3 O 4 MNPs. The obtained PB/Fe 3 O 4 composite magnetic nanoparticles were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, and X‐ray photoelectron spectroscopy. The results demonstrated that PB/Fe 3 O 4 exhibited excellent peroxidase‐like catalytic activity and followed Michaelis–Menten kinetics in the presence of H 2 O 2 and 3,3′,5,5′‐tetramethylbenzidine. Taking advantage of the intrinsic peroxidase‐like activity of PB, Fe 3 O 4 MNPs, and their synergistic effects, a novel nitrite (NO 2 − ) signal‐enhanced electrochemical sensing platform was developed by first modifying a magnetic glassy carbon electrode (MGCE) with PB and then drop‐casting the PB/ Fe 3 O 4 composite nanoparticles. The resulting PB/ Fe 3 O 4 /PB/MGCE sensor exhibited high sensitivity and selectivity toward NO 2 − detection. Under optimized conditions, the sensor achieved a detection limit of 0.03588 μM (S/N = 3). Furthermore, the proposed peroxidase‐like signal‐enhanced electrochemical sensor was successfully applied to detect NO 2 − in sausage, bacon, and pickled mustard tuber samples. Overall, this novel signal‐enhanced electrochemical sensing strategy offers great potential for applications in food quality control and safety monitoring.