USGS-NWQL: I-3561: Chemical-oxygen-demand, water-suspended-sediments, colorimetry
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Official Method Name
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Total Chemical Oxygen Demand in Water-Suspended Sediment by Dichromate Oxidation and Colorimetry |
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Current Revision
| 1985 |
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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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Organic |
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Method Source
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Citation
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Methods for the Determination of Inorganic Substances in Water and Fluvial Sediments, Techniques of Water-Resources Investigations of the United States Geological Survey, Book 5, Chapter A1 Edited by Marvin J. Fishman and Linda C. Friedman |
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Brief Method Summary
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Organic and other oxidizable materials are oxidized by digestion with an acid-dichromate solution in the presence of silver sulfate catalyst. The COD concentration is determined spectrometrically by measuring the absorbance of the Cr+3 that is formed. |
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Scope and Application
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This method may be used to analyze water-suspended sediment containing between 10 and 500 mg/L chemical oxygen demand (COD). |
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Applicable Concentration Range
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10 - 500mg/L |
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Interferences
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(1) Chloride ion, and other halides that precipitate silver. (2) Incomplete oxidation of nitrogen-containing organic matter. (3) Nitrite ion. (4) Reduced inorganic species (e.g., ferrous iron, sulfide, manganous manganese). |
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Quality Control Requirements
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Calibrate instrument using calibration standards (CAL). Quality control samples (QCS) and laboratory blanks (LB) analyzed at a minimum of I each after every 10 samples. (Reference OFR 95-443) |
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Sample Handling
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Container Description: 125 mL Glass bottle Treatment and Preservation: Bottle baked at 450 deg C by laboratory. Prepare each sample to pH<2 with H2SO4; chill and maintain at 4 deg C. DO NOT RINSE BOTTLE. |
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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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