EPA-NERL: 353.3: Nitrate-Nitrite by Cadmium Reduction and Colorimetry
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Official Method Name
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Nitrogen, Nitrate-Nitrite (Spectrophotometric, Cadmium Reduction) |
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Current Revision
| Issued 1974 |
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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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Nitrate and nitrite: A filtered sample is passed through a column containing granulated copper-cadmium to reduce nitrate to nitrite. The nitrite (originally in the sample and reduced nitrate) is determined by diazotizing with sulfanilamide and coupling with N-(1-naphthyl)-ethylenediamine dihydrochloride to form a highly colored azo dye, which is measured with a spectrometer. Nitrite alone: The procedure is the same except that the cadmium column is bypassed. |
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Scope and Application
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This method determines nitrite singly or nitrate and nitrite combined in drinking, surface, and saline waters, domestic and industrial wastes. |
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Applicable Concentration Range
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0.01 to 1.0 mg/L Nitrate-nitrite nitrogen. |
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Interferences
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(A) Suspended matter: Suspended materials will fowl the reduction column and restrict sample flow. Pretreat by filtering the sample through a 0.45 um filter or (for highly turbid samples) pretreating with zinc sulfate before filtration. (B) Metals: Metals like iron or copper can produce low results. Treat samples with EDTA to remove this interference. (C) Oil and grease: Oil and grease, that can coat the column and reduce efficiency should be removed by pre-extracting the sample with an organic solvent. |
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Quality Control Requirements
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None. |
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Sample Handling
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If analysis can be made within 24 hours, refrigerating samples at 4oC is sufficient. If samples are kept more than 24 hours, preserve with 2 mL of sulfuric acid per liter of sample and refrigerate. Do not preserve sample with mercuric chloride if they will be run through the reduction column. |
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Maximum Holding Time
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28 Days (nitrate+nitrite) 48 hours (nitrate or nitrite, singly) (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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None. |
