Determination of nitrite and glucose in water and human urine with light-up chromogenic response based on the expeditious oxidation of 3,3′,5,5′-tetramethylbenzidine by peroxynitrous acid

Abstract

Contamination of food and drinking water by dangerous levels of nitrite has always been of strong concern and toxicity of this inorganic anion calls for convenient detection methods. Although some visible approaches were developed to deal with this problem, using environmentally incompatible organic reagents or functionalized nanoparticles may greatly limit their wide applications. In this article, we report a method to visibly detect nitrite in less than 1 min at room temperature. The efficacy of the method relies on a specific reaction of HNO₂ with H₂O₂ to produce peroxynitrous acid (HOONO), which oxidizes colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to its golden yellow diimine product in seconds, with the regeneration of HNO₂. Therefore, HNO₂ can be regarded as a catalyst for the oxidation of TMB by H₂O₂. Because color visualization of the TMB–H₂O₂ system (system I) is dependent upon the concentration of HNO₂, it offers a unique avenue for the determination of nitrite. With this method, 1 μM of nitrite could be detected by the perception of yellow color in solution and less than 0.5 μM of nitrite be quantified with a spectrophotometer. The limit of detection (LOD) was 0.1 μM (S/N = 3). More interestingly, we found that the TMB–HNO₂ system (system II) could be reversibly designed to detect H₂O₂ and then glucose with the help of glucose oxidase. We evaluated the applicability of the TMB–HOONO platform in the determination of nitrite in drinking water and urinary glucose, obtaining satisfactory results. Being sensitive, selective, time-efficient, and cost-effective, the two methods derived from the three-component reaction platform are feasible for quantification of nitrite and glucose in routine laboratory practice or rapid assay outside the laboratory.