NEMI Method Summary

Method Summary Information

Method Number: I-3153 Media: WATER
Revision: Revised 1995
Method Source: U.S. Geological Survey (USGS)
Subcategory: INORGANIC Analytes in this method
Official Name: Calcium, atomic absorption spectrometric, direct-EPA
Descriptive Name Calcium, total-recoverable, water, FLAA
Source Info: USGS Branch of Information Services
Box 25286, MS 417
Federal Center
Denver, CO 80225-0286
Phone: 303-202-4700
Citation: USGS Methods, Volume A1
106807 Byte file
Brief Method
Summary:
 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.
Scope And
Application:
 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.
Applicable
Conc Range:
 0.1-60 mg/L
Interferences: 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.
QC Requirements: 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).
Sample Handling: 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.
Max Holding Time:
 180 days
 
Relative Cost: Less than $50
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