NEMI Method Summary

Method Summary Information

Method Number: I-3233 Media: WATER
Revision: 1993
Method Source: U.S. Geological Survey (USGS)
Subcategory: INORGANIC Analytes in this method
Official Name: Methods of Analysis by the U.S. Geological Survey National Water Quality Laboratory--Determination of Chromium in Water by Graphite Furrnace Atomic Absorption Spectrophotometry
Descriptive Name Chromium, whole-water-recoverable, water, GFAA
Source Info: USGS Branch of Information Services
Box 25286, MS 417
Federal Center
Denver, CO 80225-0286
Phone: 303-202-4700
Citation: U.S. Geological Survey Open-File Report 93-449
787201 Byte file
Brief Method
Summary:
 Chromium is determined by atomic absorption spectrophotometry in conjunction with a graphite furnace containing a pyrolytically coated tube and platform (Hinderberger and others, 1981). A sample is placed on the graphite platform, and a matrix modifier is added. The sample then is evaporated to dryness, pyrolized, and atomized using maximum-power heating. Maximum-power heating is a term associated with stabilized temperature platform furnace technology, which refers to a zero time ramp that allows for a 2,000<oC per second heating rate of the tube and creates the longest temperature lag between the platform and the tube wall (Carnrick and Slavin, 1989). The absorption signal produced during atomization is recorded and compared with standards.
Scope And
Application:
 This method is applicable in the range from 0.5 to 25.0 ug/L of chromium in water and water-suspended sediment. Sample solutions that contain chromium in concentrations greater than 25.0 ug/L or have a specific conductance greater than 10,000 uS/cm will need to be diluted prior to analysis or analyzed by an alternate method.
Applicable
Conc Range:
 0.5-25.0 ug/L
Interferences: Refractive elements such as chromium have the potential to form carbides. The use of pyrolytically coated tubes and platforms (Fishman and Friedman, 1989, p. 169) improves sensitivity and reduces carbide formation and memory effect.
The use of pyrolytically coated tubes and platforms in conjunction with a matrix modifier reduces the potential for interferences. Multiple natural-water samples and Standard Reference Water Samples were spiked with known concentrations of chromium with no indication of signal suppression or enhancement. These samples contained major cation concentrations as great as 300 mg/L sodium, 200 mg/L calcium, 111 mg/L magnesium, and 20 mg/L potassium; and major anion concentrations with 620 mg/L sulfate and 210 mg/L chloride.
QC Requirements: Calibrate instrument using calibration standards (CAL). Quality control sample (QCS), laboratory blank (LB), or standard (CAL) analyzed in every tenth cup. Analyze samples in duplicate (LD).
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.
Max Holding Time:
 180 days
Sample Prep Met I-3485
Relative Cost: $51 to $200
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