| Nitrite is widely existed in our surrounding environment, foods and drinks. Nitrite and amines can generate highly carcinogenic N-nitrosamine compounds. So, it is very important to establish quick, simple and sensitive methods for quantitative determination of nitrite on food safety inspection application.The chemically modified electrode (CME) was generally obtained by immobilization of some molecules, ions and polymers with excellent properties on electrode surface, which had specially chemical and physical properties. The effects of subsize, surface, interface, quantum size and macroscopic quantum tunnel for nanometer materials have become research hotspots in scientific and technological fields. Recently, the application of nano-materials as new chemically modified materials is a new trend in the field of CME. In this paper, Gd doped nano titanium dioxide, carbon nanotubes and precious metal nanoparticles were applied to construction of nitrite sensors. The main contents are summarized as follows:1. A simple gold plate electrode (GPE) based on gadolinium doped titanium dioxide (Gd/TiO2) ultrathin film was successfully constructed by using surface sol-gel technique, and used for detection of trace amount of nitride in cured food. The Gd/TiO2nanoparticles were synthesized and characterized via scanning electron microscopy (SEM) and X-ray diffraction (XRD), indicating that the Gd doped titanium dioxide formed an anatase phase through roasting at450℃, generating actively interstitial oxygen at the interface of the surface of TiO2lattice surrounded by Gd3+. Electrocatalytic effect for oxidation of nitrite on modified electrode was investigated by cyclic voltammetry in0.10mol·L-1sulfuric acid media solution, showing that the modified electrode exhibited excellent response performance to nitrite with good reproducibility, selectivity and stability. The catalytic peak current was found to be linear with nitrite concentration in the range of8.0×10-7～4.0×10-4mol·L-1, with a detection limit of5.0×10-7mol·L-1(S/N=3). The modified electrode could be used for the determination of nitrite in the cured sausage samples with a satisfactory recovery of95.7～104.3%, showing its promising application for food safety monitoring.2. Carbon nanotubes composite film modified glassy carbon electrode (MWCNTs/GCE) was fabricated on the surface of glassy carbon electrode (GCE). The morphology of the acidic nanotubes was characterized via TEM. The electrochemical behaviors of nitrite at MWCNTs/GCE were investigated by CV, the experimental conditions were optimized. Under optimal conditions, the sensing properties of MWCNTs/GCE were investigated. The oxidation peak current was linearly related to nitrite concentration in the range of2.0×10-6～8×10-4mol·L-1and the detection limit was evaluated to1.0×10-6mol·L-1. The modified electrode could be used for the determination of nitrite in the beef, claw and pickle samples with a satisfactory recovery of96.50～103.25%。3. A novel modified glassy carbon electrode based on Pt nanoparticles-zinc oxide-multiwall carbon nanotubes composite film (Pt/ZnO/MWCNTs/GCE) was prepared and tested by amperometric i-t curve (I-t) and CV. The morphology of modified electrode was characterized via SEM. The modification feasibility of different modified electrodes and the surface of electron transport capacity are characterized by CV. The electrocatalytic oxidation behavior of nitrite has been investigated using CV, and the experimental conditions were optimized. Under optimal conditions, the sensing properties of Pt/ZnO/MWCNTs/GCE were evaluated, the oxidation peak current was linearly related to nitrite concentration in the range of4.0×10-7～2.0×10-4mol·L-1and the detection limit was evaluated to2.0×10-7mol·L-1. In addition, the modified electrode exhibited good selectivity, reproducibility and stability. It was applied to the determination of nitrite levels in beef, claw and pickle with a satisfactory recovery of96.8～103.8%, indicating its potential application on food inspection. |
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