https://www.nemi.gov/methods/method_summary/4708/
Standard Methods: 4500-NO3- E: Nitrate in Water After Cadmium Reduction
Official Method Name | Nitrate in Water by Colorimetry and Cadmium Reduction |
|---|---|
Current Revision | Standard Methods Online |
Media | WATER |
Instrumentation | Spectroscopy (Colorimetry; Photometry) |
Method Subcategory | Inorganic |
Method Source | |
Citation | |
Brief Method Summary | Nitrate is reduced almost quantitatively to nitrite in the presence of Cd. The nitrite thus produced is determined by diazotizing with sulfanilamide and coupling with N-(1-napthyl)-ethylenediamine dihydrochloride to form a highly colored azo dye that is measured colorimetrically. |
Scope and Application | This method allows for determination nitrate and nitrite in water. This method will determine between 0.01 and 1 mg NO3-N/L. |
Applicable Concentration Range | 0.01 - 1.0mg/L |
Interferences | (1) Suspended matter restricts sample flow. (2) Metals (e.g., iron, copper) lower reduction efficiency. (3) Oil & Grease which coats the column. (4) Residual chlorine which oxidizes the reduction column. (5) Colored samples that absorb at ~540 nm. |
Quality Control Requirements | None |
Sample Handling | Collect 100 mL sample in a plastic or glass container. When storing sample for > 1 day, preserve with 2 mL concentrated H2SO4/L. Refrigerate at 4 C. Individual species NO3- and NO2- cannot be determined from preserved samples. Analyze within 48 hours. |
Maximum Holding Time | 48 hours |