Used primarily in biochemical assays as a chromogenic substrate for horseradish peroxidase (HRP) in Western blotting and immunohistochemistry. Upon reaction with HRP in the presence of hydrogen peroxide, it produces a stable, insoluble blue-purple precipitate at the site of enzyme activity, allowing detection of specific proteins or antigens. Its low solubility in aqueous solutions helps localize the signal, enhancing spatial resolution in membrane-based detections. Also used in some enzymatic detection systems for environmental or diagnostic testing due to its sensitivity and visible color development.