EPA-NERL: 352.1: Nitrate by Colorimetry
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Official Method Name
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Nitrogen, Nitrate (Colorimetric, Brucine) |
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Current Revision
| Issued 1971 |
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Media
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WATER |
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Instrumentation
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Spectroscopy (Colorimetry; Photometry) |
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Method Subcategory
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Inorganic |
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Method Source
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Citation
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Brief Method Summary
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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. |
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Scope and Application
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This method determines nitrate in drinking, surface and saline waters; domestic and industrial wastes. |
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Applicable Concentration Range
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0.1 - 2 mg/L nitrate-N/L. |
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Interferences
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(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. |
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Quality Control Requirements
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None. |
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Sample Handling
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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. |
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Maximum Holding Time
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48 hours (MCAWW, Table 1). |
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Relative Cost
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Less than $50 |
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Sample Preparation Methods
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