The colorimetric determination of nitrate anion in aqueous and solid samples utilizing an aromatic derivative in acidic solvent

Abstract

Ingestion of nitrates has been associated with cancer activity and other health disorders in humans. Presented here are colorimetric methods to detect and quantify nitrates from solids and liquids. A rapid spot test protocol determines nitrate anion to an amount of less than 0.10 µg. Applying a standard curve allows determination of in many samples by spectrometer. Assay by standard curve is sensitive to less than 1.00 mg/mL. In a strongly acidic mixture a brilliant blue color develops upon the reaction of nitrate anion with the secondary amine diphenylamine. An absorbance spectrum determined for the nitrated diphenylamine shows a broad absorbance peak at 597 nm and molar absorptivity of approximately 61 400 L/mole cm. The derivative that is formed is stable for more than 1 h. Inorganic salts such as phosphates, carbonates, sulfates, azides, and chlorides do not interfere with determination of nitrates. Groundwater, pond water, and dust particles were analyzed for nitrates. These methods are rapid, sensitive, relatively inexpensive, do not require complex instrumentation, and are useful for solid and liquid samples. The acidic solvent will dissolve sample components not soluble in water and results are easily discerned by eye. The reagent may easily be transported.