Used as a reagent in the colorimetric determination of nitrites in water, food, and biological samples. It reacts with sulfanilamide in acidic conditions to form a diazonium salt that couples with this compound to produce a pink azo dye, measurable by spectrophotometry. Commonly applied in environmental monitoring to assess nitrate/nitrite levels in drinking water and wastewater. Also utilized in biochemical assays for nitric oxide detection, due to its conversion to nitrite in biological systems. Employed in agriculture to test soil nitrate content, supporting fertilizer management. Its high sensitivity makes it suitable for trace analysis in quality control laboratories.