EPA-NERL: 350.1: Ammonia by Automated Colorimetry
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Official Method Name
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Nitrogen, Ammonia (Colorimetric, Automated Phenate) |
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Current Revision
| Revision 2.0. August 1993 |
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Media
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WATER |
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Instrumentation
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Automated Spectrophotometer |
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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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Alkaline phenol and hypochlorite react with ammonia to form indophenol blue that is proportional to the ammonia concentration. The blue color is intensified with sodium nitroprusside. |
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Scope and Application
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This method determines ammonia in drinking, surface, and saline waters; domestic and industrial wastes. |
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Applicable Concentration Range
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0.01 - 2.0 mg/L (ammonia as N) |
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Interferences
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(A) Calcium and Magnesium: Ions of these metals can cause errors by precipitating during analyses. Use EDTA solution (for river and industrial waters) or potassium tartrate solution (for sea water) to reduce this interference. (B) Turbidity: Sample turbidity should be removed by filtration. (C) Color: Color absorbing in the range of the indophenol blue complex can interfere. |
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Quality Control Requirements
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None. |
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Sample Handling
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Cool to 4oC, add H2SO4 until sample pH < 2. |
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Maximum Holding Time
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28 days (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. |
