EPA-NERL: 352.1:  Nitrate by Colorimetry

  • Summary
  • Analytes
  • Revision
  • Data and Sites
Official Method Name
Nitrogen, Nitrate (Colorimetric, Brucine)
Current Revision
Issued 1971
Spectroscopy (Colorimetry; Photometry)
Method Subcategory
Method Source
  Methods for the Chemical Analysis of Water and Wastes (MCAWW) (EPA/600/4-79/020)
Brief Method Summary
This method is based upon the reaction of the nitrate ion with brucine sulfate in a concentrated sulfuric acid solution at 100oC. The color complex is measured colorimetrically.
Scope and Application
This method determines nitrate in drinking, surface and saline waters; domestic and industrial wastes.
Applicable Concentration Range
0.1 - 2 mg/L nitrate-N/L.
(A) Dissolved organic matter: Dissolved organic matter will cause an off color in sulfuric acid, and must be compensated with additions of all reagents except the brucine-sulfanilic acid reagent. This also applies to natural colors.
Salinity: The effect of salinity is eliminated by addition of sodium chloride to blanks, standards, and samples.
Oxidizing & Reducing Agents: All stong oxidizing and reducing agents interfere. Chlorine can be eliminated with sodium arsenite.
Iron and Manganese: Ferrous and ferric iron and quadrivalent manganese give slight positive interference, but for concentrations less than 1 mg/L this interference is negligible.
Uneven heating: Uneven heating of samples and standards during the reaction time will result in erratic results.
Quality Control Requirements
Sample Handling
Perform analysis as soon as possible. If analysis is made within 24 hours, refrigerate sample at 4 degrees C prior to analysis. If samples will not be analyzed within 24 hours, preserve with sulfuric acid and refrigerate.
Maximum Holding Time
48 hours (MCAWW, Table 1).
Relative Cost
Less than $50
Sample Preparation Methods