USGS-NWQL: I-3239: Cobalt, total-recoverable, water, FLAA
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Official Method Name
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Cobalt, atomic absorption spectrometric, direct |
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Current Revision
| Revised 1985 |
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Media
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WATER |
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Instrumentation
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Flame Atomic Absorption |
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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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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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Cobalt is determined by atomic absorption spectrometry by direct aspiration of the sample into an air-acetylene flame without additional treatment of the sample other than the addition of ammonium chloride to mask certain interferences. |
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Scope and Application
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This method may be used to analyze water and water-suspended sediment containing at least 50 ug/L of cobalt. Samples solutions containing more than 1,000 ug/L need either to be diluted or to be read on a less expanded scale. Sample solutions containing less than 50 ug/L need to be analyzed by the atomic absorption spectrometric chelation-extraction method, providing the interference limits discussed in that method are not exceeded. Total recoverable cobalt in water-suspended sediment needs to undergo preliminary digestion-solubilization by method I-3485, and recoverable cobalt in bottom material needs to undergo preliminary digestion-solubilization by method I-5485 before being determined. |
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Applicable Concentration Range
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50-1000 |
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Interferences
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Nitrate at 1 mg/L interferes by suppressing the absorption of the cobalt. This interference is eliminated in solutions containing about 18,000 mg/L of ammonium chloride. Samples adjusted to this concentration of ammonium chloride show no interference from 800 mg/L of nitrate. Individual concentrations of sodium (9,000 mg/L), potassium (9,000 mg/L), calcium (4,500 mg/L), magnesium (4,500 mg/L), sulfate (9,000 mg/L), chloride (15,000 mg/L), iron (4 X 106 ug/L), and cadmium, nickel, copper, zinc, lead, and chromium (10,000 ug/L) do not interfere. Higher concentrations of each constituent were not investigated. |
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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: 250 mL Polyethylene bottle, acid-rinsed. Treatment and Preservation: Use unfiltered sample to rinse bottles, then acidify collected sample with HNO3 to pH < 2. |
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Maximum Holding Time
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180 days |
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Relative Cost
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Less than $50 |
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Sample Preparation Methods
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I-3485 |
