Iron Oxide, Reduced Graphene Oxide, and Electrodeposited Gold Nanoparticle-Based Electrodes for Nanomolar Detection of Nitrite in Food

The nitrite ion (NO 2 – ) is used as a preservative of food and drink and has been widely used in the food industry. Nonetheless, it is a potential precursor of nitrosamines, which are known for their carcinogenic activity. Therefore, monitoring of nitrite in foods and drinks is of paramount importance for food safety. Herein, we report a very sensitive electroanalytical method for the determination of nitrite in food samples, capable of detecting nitrite at the nanomolar level. For that purpose, a nanocomposite electrode comprising a multilayered film of iron oxide nanoparticles and reduced graphene oxide (ION-RGO) was decorated with electrodeposited gold nanoparticles (AuNP) and operated by electrochemical impedance spectroscopy (EIS). It is observed a synergistic combination of the electrocatalytic activity of ION-RGO, the electrical conductivity of AuNP, and the interrogation of the electrode within the charge-transfer frequency range, which mitigates unwanted capacitive effects and enhances the nitrite electrooxidation. Consequently, nitrite has been detected within a wide linear range ( r 2 > 0.999) of 0.58–3019 μM and with a limit of detection of 2.4 nM. Owing to the improved adhesion of AuNP to the ION-RGO framework, the electrode is highly stable and lasts for at least 30 consecutive runs without losing its sensitivity. Additionally, the proposed method enables the determination of nitrite in sausage and milk samples, when it performs identically to a reference method at the 95% confidence level.