Evaluating nitrite content changes in some Chinese home cooking with a newely-developed CDs diazotization spectrophotometry.

The research developed a diazo-coupling carbon-dots (CDs) method for determining nitrite and optimized variables of sodium sulfanilate, CDs synthesis, characteristic wavelength, reaction time and temperature. The method can assay 0.025-2.0 mg/L NO2- and has a detection limit of 9.6 μg/L and 95-105% recovery. Subsequently, it was applied in detecting NO2- changes in some Chinese home cooking, the gotten results indicated that if the sautéed vegetables (cabbage, Chinese cabbage, spinach and lettuce) and stir-fry pork, fried peas and pickled vegetable are stored at 4 °C for 72 h, nitrite contents are far lower than the recommended value, but if stored at room temperature for 24 h, the content in pure vegetables and shredded pork with green pepper will exceed the recommended value. Therefore, the staying fresher for the sautéed vegetables at room temperature is 24 h, if stored in a refrigerator at 4 °C, their staying fresher can be extended to 72 h.