Standard Methods: 4500-NO2- B: Nitrite by Colorimetry
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Official Method Name
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4500-NO2- B. Colorimetric Method |
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Current Revision
| Standard Methods Online |
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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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Nitrite is determined through formation of a reddish purple azo dye produced at pH 2.0 to 2.5 by coupling diazotized sulfanilamide with N-(1-naphthyl)-ethylenediamine dihydrochloride (NED dihydrochloride). |
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Scope and Application
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The colorimetric method is suitable for determining concentrations of 5 to 1000 ug NO2--N/L in water. |
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Applicable Concentration Range
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5-50 ug-N/L or 10-1,000 ug-N/L |
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Interferences
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Chemical incompatibility makes it unlikely that nitrite, free chlorine, and nitrogen trichloride (NCl3) will coexist. NCl3 imparts a false red color when color reagent is added. The following ions interfere because of precipitation under test conditions and should be absent: Sb (III), Au (III), Bi (III), Fe (III), Pb (II), Hg (II), Ag (I), chloroplatinate [PtCl6(2-)], and metavanadate [VO3(2-)]. Cupric ion may cause low results by catalyzing decomposition of the diazonium salt. Colored ions that alter the color system also should be absent. |
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Quality Control Requirements
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See Section 4020 Quality Assurance/Quality Control. |
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Sample Handling
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Plastic or glass containers. Never use acid preservation for samples to be analyzed for nitrite. Make the determination promptly on fresh samples to prevent bacterial conversion of nitrite to nitrate or ammonia. For short-term preservation for 1 to 2 d, freeze at -20 degrees C or store at 4 degrees C. |
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Maximum Holding Time
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48 hours (regulatory) (See Section 1060) |
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Relative Cost
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Less than $50 |
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Sample Preparation Methods
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