Used as a chromogenic substrate in enzyme-linked immunosorbent assays (ELISAs) for detecting peroxidase activity. It produces a blue color upon oxidation, making it useful in diagnostic tests for detecting antibodies, antigens, or proteins. Commonly applied in medical diagnostics, research laboratories, and biochemical studies to quantify biomarkers or study enzymatic reactions. Its sensitivity and stability make it a preferred choice in various immunoassays.