Rapid colorimetric determination of nitrate in plant tissue by nitration of salicylic acid

TLDR

The authors are experienced agronomists and research chemists affiliated with the U.S. Department of Agriculture. The study presents a rapid method to quantify nitrate‑N in plant extracts. The method relies on nitration of salicylic acid under acidic conditions to form a chromophore that absorbs maximally at 410 nm in basic solutions, with absorbance proportional to nitrate‑N concentration. The assay is selective, with no interference from ammonium, nitrite, or chloride ions.

Abstract

Abstract An analysis is described for the rapid determination of nitrate‐N in plant extracts. The complex formed by nitration of salicylic acid under highly acidic conditions absorbs maximally at 410 nm in basic (pH>12) solutions. Absorbance of the chromophore is directly proportional to the amount of nitrate‐N present. Ammonium, nitrite, and chloride ions do not interfere. Key words: nitrosalicylic acidnitrate determination Notes Cooperative Investigation, Agricultural Research Service, U.S. Department of Agriculture, and the Agricultural Experiment Station, University of Wisconsin‐Madison. Research supported by the College of Agricultural and Life Sciences, University of Wisconsin‐Madison, by USDA Cooperative Agreement 12–14–100–10,888, and by an award from the UN Graduate School Research Committee. Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may also be suitable. Former Postdoctoral Fellow, Graduate Research Assistant, Associate Professor of Agronomy, and Research Chemist, U.S. Department of Agriculture. (VLY is also Associate Professor of Agronomy). Present address of DAC: Battelle, Pacific Northwest Laboratories, Ecosystems Department, Richland, Washington 99352.