Enhanced electrochemical detection of sodium nitrite in food samples using Fe3O4@Au-MoS2/polyoxometalate composite films

Abstract

Nitrite (NO2-) is commonly used as a food additive; however, excessive intake can lead to the formation of carcinogens in the human body, highlighting the need for sensitive detection of NO2-. In this study, molybdenum disulfide (MoS2) was combined with gold magnetic nanoparticles to prepare a composite material designated as Fe3O4@Au-MoS2 using a hydrothermal method. A composite film, [P2W17V/PEI]n/Fe3O4@Au-MoS2/GCE (n=1-5) (abbreviated as Fe3O4@Au-MoS2/P2W17V), was developed based on Fe3O4@Au-MoS2 and the polyoxometalate (K7P2W17VO62·18H2O, P2W17V) for the electrochemical detection of nitrite, achieving high sensitivity and selectivity. The performance of the composite film was evaluated using various electrochemical techniques, including cyclic voltammetry (CV), differential pulse voltammetry (DPV), chronoamperometry (i-t), and electrochemical impedance spectroscopy (EIS). The detection system was optimized to enhance its performance. The effective integration of Fe3O4@Au-MoS2 and P2W17V facilitates efficient electron capture during the redox reaction, thereby improving the conductivity of the electrical signals and increasing the sensitivity of the nitrite detection system. Under optimized conditions, the sensor exhibited a linear response for nitrite detection in the ranges of 0.1-100 mmol/L and 100-750 mmol/L, with a limit of detection (LOD) of 0.243 μmol/L (S/N = 3). Additionally, recoveries for real sample analysis ranged from 97.9% to 111.3%, with a relative standard deviation (RSDs) of less than 4%. These results demonstrate that the developed electrochemical sensor is suitable for the detection of nitrite across a wide range of real samples, underscoring its potential applications in food safety monitoring.