A naphthalimide-based fluorescent probe for rapid detection of nitrite and its application in food quality monitoring

Nitrite (NO2-) is a widely used food additive and long-term aging of cooked leftovers may also contribute to the formation of NO2-, excessive consumption of NO2- is harmful to human health. Developing an effective sensing strategy for on-site monitoring of NO2- has attracted considerable attention. Herein, a novel colorimetric and fluorometric probe ND-1 based on photoinduced electron transfer effect (PET) was designed for highly selective and sensitive detection of nitrite (NO2-) in foods. The probe ND-1 was strategically constructed by employing naphthalimide as the fluorophore and o-phenylendiamine as the specific recognition site for NO2-. The triazole derivative ND-1-NO2- could be produced exclusively by reacting with NO2-, leading to a visible colorimetric change from yellow to colorless accompanied by a significantly enhanced fluorescence intensity at 440 nm. The probe ND-1 exhibited promising sensing performances towards NO2- including high selectivity, rapid response time (within 7 min), low detection limit (47.15 nM) and wide quantitative detection range (0-35 μM). In addition, probe ND-1 was capable of quantitative detecting of NO2- in real food samples (including pickled vegetables and cured meat products) with satisfactory recovery rates (97.61%-103.08%). Moreover, the paper device loaded by probe ND-1 could be utilized for visual monitoring of NO2- levels variation of stir-fried greens. This study provided a feasible method for the accurate, traceable and rapid on-site monitoring NO2- in foods.