USGS-NWQL: I-3152: Calcium, total-recoverable, water, FLAA
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Official Method Name
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Calcium, 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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Calcium is determined by atomic absorption spectrometry (Fishman and Downs, 1966). Lanthanum chloride is added to mask interferences. This procedure may be automated by the addition of a sampler, a proportioning pump, and a strip-chart recorder or printer or both (fig. 1). |
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Scope and Application
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This method maybe used to analyze atmospheric precipitation, water, brines, and water-suspended sediment. Two analytical ranges for calcium are included: from 0.01 to 5.0 mg/L and from 1.0 to 60 mg/L. Sample solutions containing calcium concentrations greater than 60 mg/L need to be diluted. Total recoverable calcium in water-suspended sediment needs to undergo preliminary digestion-solubilization by method I-3485, and recoverable calcium 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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0.1-5.0 mg/L 1.0-60 mg/L |
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Interferences
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Phosphate, sulfate, and aluminum interfere but are masked by the addition of lanthanum. Silica also reportedly interferes. Because low calcium values result if the pH of the sample is above 7, standards are prepared in hydrochloric acid solution and samples are preserved in the field with use of nitric acid solution. Concentrations of magnesium greater than 1,000 mg/L also cause low calcium values. Nitrate interferes, but in the presence of lanthanum chloride-hydrochloric acid solution at least 2,000 mg/L can be tolerated. The addition of nitric acid to the sample causes no problem in the following procedure. |
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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-rinse. 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 |
