Widely used in enzyme-linked immunosorbent assays (ELISA), this substrate delivers high sensitivity when detecting horseradish peroxidase (HRP) activity. It produces a stable blue color upon oxidation, allowing visual or spectrophotometric detection. The reaction is easily stopped with acid, shifting the color to yellow for optimized absorbance reading. Commonly applied in medical diagnostics, food safety testing, and research labs for detecting antigens and antibodies. Its low toxicity compared to similar substrates makes it suitable for routine lab use. Also employed in western blotting and other immunochemical techniques requiring clear, consistent signal development.