Simple strategy for dual-responsive ratio electrochemical-colorimetric detection of nitrite in food and environment.

A dual-responsive ratio electrochemical-colorimetric method for nitrite (NO) is established based on the combination of nanoenzyme (MnO) catalysis with diazotization reactions. The MnO can oxidize colorless 3,3',5,5'-tetramethylbenzidine (TMB) into blue TMBox. The NO induces the diazotization reaction of TMBox, leading to a decrease of  the signal at 652 nm and the generation of a new signal from diazotized TMBox at 445 nm. Furthermore, the presence of NO reduces the electrochemical oxidation signal of TMB and simultaneously provides its electrochemical signal. Compared with traditional single-mode detection, dual-mode detection offers higher sensitivity, lower detection limits, and better interference resistance. The inherent advantages of this method make it feasible to detect NO in real samples, offering broad prospects for applications in food safety and environmental monitoring.