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

A dual-responsive ratio electrochemical-colorimetric method for nitrite (NO₂⁻) is established based on the combination of nanoenzyme (Mn₃O₄) catalysis with diazotization reactions. The Mn₃O₄ can oxidize colorless 3,3′,5,5′-tetramethylbenzidine (TMB) into blue TMBox. The NO₂⁻ 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 NO₂⁻ 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 NO₂⁻ in real samples, offering broad prospects for applications in food safety and environmental monitoring.