USGS-NWQL: I-4243:  Cobalt, whole-water-recoverable, water, GFAA

  • Summary
  • Analytes
  • Revision
  • Data and Sites
Official Method Name
Cobalt, atomic absorption spectrophotometry, graphite furnace
Current Revision
Revised 1989
Media
WATER
Instrumentation
Graphite Furnace-Atomic Absorption Spectrometer
Method Subcategory
Inorganic
Method Source
  USGS-NWQL
Citation
M.J. Fishman, 1993, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory--Determination of inorganic and organic constituents in water and fluvial sediments: U.S. Geological Survey Open-File Report 93-125
Brief Method Summary
Cobalt is determined by atomic absorption spectrophotometry in conjunction with a graphite furnace containing a graphite platform (Hinderberger and others, 1981). A sample is placed on the graphite platform, and the sample then is evaporated to dryness, charred, and atomized using high-temperature ramping. The absorption signal produced during atomization is recorded and compared with standards.
Scope and Application
This method is used to determine cobalt in samples of water and water-suspended sediment with a specific conductance not greater than 10,000 uS/cm. With Zeeman background correction and a 20-uL sample, the method is applicable in the range from 1 to 25 ug/L. Sample solutions that contain cobalt concentrations greater than 25 ug/L must be diluted or be analyzed by an alternate method. This method was implemented in the National Water Quality Laboratory in May 1989.
Whole water recoverable cobalt in samples of water-suspended sediment must undergo preliminary digestion by method I-3485 before being determined.
Applicable Concentration Range
1-25 ug/L
Interferences
Interferences for samples with specific conductances less than 10,000 uS/cm normally are small. In addition, the use of the graphite platform reduces the effects of many interferences.
Special precautionary measures to prevent contamination need to be used during sample collection and laboratory determination.
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-rinsed.
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
$51 to $200
Sample Preparation Methods
I-3485