USGS-NWQL: I-3153: Calcium, total-recoverable, water, FLAA
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Official Method Name
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Calcium, atomic absorption spectrometric, direct-EPA |
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Current Revision
| Revised 1995 |
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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. Effluent samples must undergo a preliminary nitric acid digestion followed by a hydrochloric acid solubilization. |
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Scope and Application
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This method may be used to analyze water-suspended sediment. Sample solutions containing from 0.1 to 60 mg/L of calcium may be analyzed without dilution; whereas, those containing more than 60 mg/L need to be diluted. For ambient water, analysis may be made on a measured portion of the acidified water-suspended sediment sample. For all other waters, including domestic and industrial effluent, the atomic absorption procedure must be preceded by a digestion-solubilization as specified (in the method). In cases where the analyst is uncertain about the type of sample, the digestion-solubilization procedure must be used. |
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Applicable Concentration Range
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0.1-60 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 reportedly also 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 as a preservative at the time of collection causes no problem in the following procedure. Samples should be evaporated just to dryness following nitric acid digestion to avoid any possible nitrate interference. |
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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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