3,3',5,5'-Tetramethylbenzidine (TMB) is a high-sensitivity, low-toxic chromogenic substrate widely used in biochemical detection and immunoassay fields. Compared with traditional benzidine reagents, it features non-carcinogenic performance and stable chromogenic reaction, serving as an ideal alternative toxic-free indicator. It specifically reacts with horseradish peroxidase (HRP) and hydrogen peroxide to produce stable blue-green oxidized products, with accurate absorbance detection at 620–650 nm, which is core to ELISA enzyme-linked immunosorbent assay. It is extensively applied in medical diagnosis, biological reagent detection, food safety testing and environmental monitoring. In immunological experiments, it enhances detection sensitivity and reduces background interference, ensuring accurate qualitative and quantitative analysis of antigens and antibodies. Additionally, it acts as a common chromogenic agent for immunohistochemistry, biochemical staining and enzyme activity detection. It can also be used as a key raw material for preparing biochemical detection kits and laboratory standard reagents. With excellent reaction specificity and safety, it has become one of the most essential chromogenic substrates in modern biochemistry and analytical testing industries.

This biochemical reagent has low toxicity but certain irritant effects on human tissues. Inhalation of fine dust may irritate the respiratory tract, causing throat discomfort and mild cough. All handling operations should be performed in well-ventilated laboratory environments with dust-proof masks and protective gloves. Direct skin contact may cause dryness, redness and itching; prolonged contact may trigger mild allergic dermatitis. Eye contact will lead to stinging irritation and conjunctival redness. In case of accidental exposure, rinse the affected area with plenty of running water for more than 15 minutes. The product is sensitive to light and heat, prone to oxidative deterioration under high temperature and strong light conditions. Thermal decomposition generates toxic nitrogen oxide fumes, which are harmful to human health. Keep away from strong oxidants, high heat and direct sunlight during storage and use. Do not store together with food and daily chemical supplies. All waste residues and contaminated experimental waste shall be classified and disposed of as laboratory hazardous waste to avoid environmental pollution and personal health risks.