USGS-NWQL: I-3152:  Calcium, total-recoverable, water, FLAA

  • Summary
  • Analytes
  • Revision
  • Data and Sites
Official Method Name
Calcium, atomic absorption spectrometric, direct
Current Revision
Revised 1985
Media
WATER
Instrumentation
Flame Atomic Absorption
Method Subcategory
Inorganic
Method Source
  USGS-NWQL
Citation
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
Brief Method Summary
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).
Scope and Application
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.
Applicable Concentration Range
0.1-5.0 mg/L
1.0-60 mg/L
Interferences
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.
Quality Control 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.
Maximum Holding Time
180 days
Relative Cost
Less than $50
Sample Preparation Methods
I-3485