DOE: MS310: Nitrate in Water by Colorimetric Test
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Official Method Name
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Determination of Nitrate Ions (NO3) in Water and Soil Samples Using the Indicator Strip-Based Colorimetric Test |
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Current Revision
| 1997 |
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Media
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WATER |
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Instrumentation
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Color Strip Indicator |
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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 nitrate test strip is immersed in an aqueous sample (soil samples are first extracted with deionized water). The outer reaction zone of the nitrate test strip contains a reducing agent that takes nitrate to nitrite. The pale yellow-colored reaction zone changes to white for negative samples and to varying shades of red-violet in the range of 5 to 500 ppm nitrate. After 1 minute, the nitrate content of the sample is estimated by comparing the color of the strip with a standard color chart. The intensity of color is proportional to nitrate concentration. |
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Scope and Application
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This field method screens for the presence of nitrate in aqueous and soil samples. |
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Applicable Concentration Range
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0.005 - 0.5 mg/mL |
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Interferences
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(1) Nitrite produces false-positives. (2) Oxidizing anions interfere with intensity of reaction zone, causing an underestimate of nitrate. (3) Presence of certain cations may interfere with intensity of reaction zone, causing an underestimate of nitrate. |
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Quality Control Requirements
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Test samples of test strips from each batch using solutions of known nitrate concentrations. |
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Sample Handling
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Perform the test in the field. Dispose the samples at their collection source. |
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Maximum Holding Time
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Relative Cost
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Less than $50 |
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Sample Preparation Methods
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