ASTM: D3867: Nitrate-Nitrite in Water by Automated Cadmium Reduction
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Official Method Name
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Automated Cadmium Reduction; Nitrite-Nitrate Automated Cd Reduction (Test Method A) |
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Current Revision
| 1990 |
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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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The applicable range of this test method is from 0.05 to 1 mg/L of nitrite or nitrate nitrogen. The range may be extended upward by dilution of an appropriate aliquot. Many workers have found that this test method is reliable for nitrite and combined nitrite-nitrate levels to 0.01 mg N/L. However, the precision and bias data presented in this test method are insufficient to justify application of this test method in the 0.01 to 0.05 mg N/L range. This test method is applicable to surface, saline, waste, and ground waters. It is the user's responsibility to ensure the validity of this test method for waters of untested matrices. |
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Scope and Application
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A filtered sample is passed through a column containing copper coated cadmium granules to reduce nitrate ion to nitrite ion. The combined nitrite-nitrate nitrogen is determined by diazotizing the total nitrite ion with sulfanilamide and coupling with N-(1-naphthyl)ethylenediamine dihydrochloride to form a highly colored azo dye that is measured spectrophotometrically. The nitrite ion originally present in the sample can be determined separately by carrying out the procedure and omitting the cadmium reduction step. The nitrate ion can be calculated as the difference between the combined nitrite-nitrate nitrogen and the nitrite nitrogen. |
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Applicable Concentration Range
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0.05 - 1.0mg/L |
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Interferences
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(1) Turbid samples. (2) Sample color that absorbs at wavelengths between 520 and 540 nm. (3) Oil and grease. (4) Certain metal ions in concentrations above 35 mg/L. (5) Excessive amounts of chlorine will deactivate reducing column. (6) In acid samples (pH less than 4.5) nitrate is not reduced in cadmium column. |
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Quality Control Requirements
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Sample Handling
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Collect the sample in accordance with D3370, as applicable. Analyze samples soon after collection. Preserve samples to be analyzed within 24 hours by refrigeration at 4 degrees C. Preserve samples stored for more than 24 hours with 2 mL of concentrated H2SO4/L and refrigerate at 4 degrees C. |
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Maximum Holding Time
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24 hours (w/o acid) |
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Relative Cost
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Less than $50 |
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Sample Preparation Methods
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