Electrochemical Sensor Based On Copper Nitrogen-doped Carbon-derived Materials For The Detection Of Nitrite In Food

Nitrite,as one of the most common nitrogen-containing compounds in nature,widely exists in water,soil,and food.Excessive intake of nitrite can lead to iron deficiency anemia,fetal malformation and,more seriously,cancer.Therefore,the determination of nitrite content is particularly important to human health and food safety.The common detection techniques for nitrite include chromatography,chemiluminescence,fluorescence spectroscopy,spectrophotometry,capillary electrophoresis,electrochemical methods and so on.Among them,the electrochemical detection method has the advantages of small test tools,low cost,fast response,and high sensitivity.With the further improvement of electrocatalytic activity of modified materials,electrochemical sensing is expected to develop into a test method to realize on-site rapid detection.In order to improve the catalytic performance of the electrode and increase the electrocatalytic oxidation ability of the sensor to nitrite,a new nitrite electrochemical sensor with fast,high sensitivity and low detection limit was constructed by modifying the electrode with copper nitrogen doped carbon derived material,and the residue of nitrite in food was analyzed and detected.It is mainly divided into the following two parts:（1）Using lignin as carbon source and copper ion as metal source,Cu NPs/N-LC material was produced by coprecipitation and high temperature calcination,and an electrochemical sensor for detecting nitrite was constructed.The morphology and structure of Cu NPs/N-LC were analyzed and characterized by SEM,HRTEM,XRD and XPS.The electrochemical performance of the sensor was tested by cyclic voltammetry curve,chronocoulometry curve and chronoamperometry curve,and the nitrite in pickles was quantitatively detected.Under the optimized experimental conditions,the oxidation current of nitrite showed a good linear relationship with concentration in the range of 5×10^-3-1 mmol·L^-1 and 1-5 mmol·L^-1,and the detection limit in low concentration range was 0.066μmol·L^-1（S/N=3）with a sensitivity of123μA·m M^-1·cm^-2.The constructed sensor has good anti-interference ability,reproducibility and stability.The recoveries of nitrite in pickles ranged from 98.23%to 99.75%.（2）Using tannic acid as reducing agent and carbon source,potassium chloride as template and copper ion as metal source,Cu N-TAC material was prepared by coprecipitation and high temperature calcination to construct nitrite electrochemical sensor.The modified electrode was characterized by SEM,HRTEM,XRD,XPS and BET.The detection performance of the modified electrode for nitrite was verified by cyclic voltammetry and amperometric detection.Under the optimum experimental conditions,there was an irreversible oxidation peak of NO₂^-at 0.75 V,indicating that the oxidation process of nitrite on the electrode surface is completely irreversible.The concentration of NO₂^-was positively correlated with the current in the range of 5×10^-5-10 mmol·L^-1,the detection limit was 0.009μmol·L^-1（S/N=3）and the sensitivity was328.025μA·m M^-1·cm^-2.The recoveries for detection of nitrite in sausage samples ranged from98.59 to 100.09%.In conclusion,this study developed a fast,highly sensitive and ultra-low detection limit nitrite electrochemical sensor based on copper nitrogen doped carbon derived materials,and effectively detected the residue of nitrite in food.It not only provides theoretical support for the design and preparation of new electrochemical sensors with enzyme like activity,but also broadens the application of copper nitrogen doped carbon drived materials in the field of food safety.