EPA-NERL: 353.2: Nitrate-Nitrite Nitrogen by Colorimetry
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Official Method Name
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Nitrogen, Nitrate-Nitrite (Colorimetric, Automated, Cadmium Reduction) |
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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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A filtered sample is passed through a column containing granulated copper-cadmium to reduce nitrate to nitrite. The nitrite (that originally present plus that reduced to 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 colorimetrically. Separate, rather than combined nitrate-nitrite, values are readily obtained by carrying out the procedure first with, and then without, the Cu-Cd reduction step. |
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Scope and Application
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This method pertains to the determination of nitrite singly, or nitrite and nitrate combined in surface and saline waters; and domestic and industrial wastes. |
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Applicable Concentration Range
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0.05 - 10 mg/L |
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Interferences
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(1) Build up of suspended matter in the reduction column will restrict sample flow. Since nitrate-nitrogen is found in a soluble state, the sample may be pre-filtered. (2) High concentrations of iron, copper, or other metals. (3) Large concentrations of oil and grease will coat the surface of the cadmium. |
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Quality Control Requirements
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Not included. |
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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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$51 to $200 |
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Sample Preparation Methods
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