A rapid colorimetric method for analysis of nitrate nitrogen by reduction to nitrite

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Abstract
A new method was developed for the determination of nitrate based on a soluble powder containing zinc and a bluish diazotizing solution. In this procedure about 10% of the nitrate content of the sample is converted to nitrite, but the intensity of the color developed is proportional to the nitrate content. The color changes from blue through green to yellow. The nitrate concentration can be estimated visually or determined spectrophotometerically at λmax 400 nm in the range of 4–40 mg/L N. When the color change is very small, a coupling solution is added, and the violet color that develops can be measured colorimetrically at λ max 545 nm in the range of 0.5–5 mg/L N. This simple method employs harmless chemicals and is especially suitable for use in agriculture. Reliable results are obtained in less than 10 minutes.
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