A modified spectrophotometric method for nitrate in plants,soils and water by nitration of 3,4-dimethylphenol

A spectrophotometric method suitable for rapid and precise routine analysis of plant tissue, soils and water samples with a wide range of nitrate nitrogen values is described. Ethanol replaces the acetone sometimes used as solvent for the 3,4-dimethylphenol reagent, so that spectral interference caused by acetone is eliminated. The time required for complete nitration of the reagent is reduced from 25 min to that required for mixing of reactants. Chloride ion levels of up to 6.0% in plant tissue, 1940 μg g^-1 and 970 μg ml^-1 in soil and water, respectively, do not interfere. The probable reaction mechanism of acetone interference is discussed.