USGS-NWQL: I-1241: Cobalt, dissolved, water, GFAA
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Official Method Name
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Cobalt, atomic absorption spectrometric, graphite furnace |
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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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Graphite Furnace-Atomic Absorption Spectrometer |
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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 in conjunction with a graphite furnace containing a graphite platform (Hinderberger and others, 1981). A sample is placed on the graphite platform, then evaporated to dryness, charred, and atomized using high-temperature ramping. The absorption signal generated during atomization is recorded and compared with standards. |
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Scope and Application
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This method may be used to determine cobalt in low ionic-strength water and precipitation. With deuterium background correction and a 20-uL sample, the method is applicable in the range from 0.5 to 100 ug/L. With Zeeman background correction and a 20-uL sample, the method is applicable in the range from 0.5 to 65 ug/L. Sample solutions that contain cobalt concentrations exceeding the upper limits must be diluted or preferably be analyzed by the atomic absorption spectrometric direct or chelation-extraction method, or by the atomic emission spectrometric ICP method. The analytical range and detection limits can be increased or possibly decreased by varying the volume of sample injected or the instrumental settings. Purification of reagents and use of ASTM Type 1 water (Method D-1193, American Society for Testing and Materials, 1984) may result in lower detection limits. |
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Applicable Concentration Range
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0.5-100 ug/L Deuterium 0.5-65 ug/L Zeeman |
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Interferences
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Interferences in low ionic-strength samples, such as precipitation, normally are quite low. In addition, the use of the graphite platform reduces the effects of many interferences. Calcium (60 mg/L), magnesium (14 mg/L), sodium (55 mg/L), sulfate (110 mg/L), and chloride (45 mg/L) do not interfere. Higher concentrations of these constituents were not investigated. Precipitation samples usually contain very low concentrations of cobalt. Special precautionary measures must be employed during both sample collection and laboratory determination to prevent contamination. |
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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: Filter through 0.45-um filter, use filtered sample to rinse containers and acidify 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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$51 to $200 |
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Sample Preparation Methods
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