A method is presented which allows rapid nitrate analyses of water and waste water samples and soil extracts. The linear working range is typically 0.5–30 mg NO−3‐N/liter and duplicate analysis of samples and standards routinely produces confidence limits for the regression estimate of ‐ ±0.1 mg NO−3‐N/liter at the 95% confidence level. Nitrite, formaldehyde and soluble Iron, as Fe3+, cause a positive Interference, while chloride causes a negative interference. The extent of the Interference is a function of the amount of nitrate present.