Highly efficient redox reaction between potassium permanganate and 3,3′,5,5′-tetramethylbenzidine for application in hydrogen peroxide based colorimetric assays

Potassium permanganate (KMnO ₄ ) is one of the most important oxidants, which plays important roles in many fields. Here, we found that KMnO ₄ could directly induce the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to generate an oxidized product with a color change. This redox reaction is highly efficient, and 1 μM KMnO ₄ is enough to cause detectable changes in the absorbance signal. Meanwhile, this reaction is very fast and the generated blue product can stabilize for a relatively long period, which has great advantages in practical applications. Since hydrogen peroxide (H ₂ O ₂ ) is able to react with KMnO ₄ under acidic conditions, the KMnO ₄ -TMB system can be used for the detection of H ₂ O ₂ ; the absorbance signal induced by 5 μM H ₂ O ₂ can be easily detected in this method. Meanwhile, the KMnO ₄ -TMB system can also be used for the detection of glucose by monitoring the generation of H ₂ O ₂ , which is the main product of glucose oxidation; this method permits detection of concentrations as low as 10 μM glucose, and the sensitivity is comparable to or higher than most peroxidase mimetic based methods, but avoiding the preparation and storage of the nanomaterials. Furthermore, the KMnO ₄ -TMB system can even be used for analyzing glucose in serum samples, which can also be expected to be used in immunoassays.