NEMI Method Summary

Method Summary Information

Method Number: 206.4 Media: WATER
Revision: Issued 1971; Editorial Revision 1974
Method Source: U.S. EPA National Exposure Research Laboratory (NERL) [formerly EMSL]
Analytes in this method
Subcategory: INORGANIC
Official Name: Arsenic (Spectrophotometric-SDDC)
Descriptive Name Arsenic by Spectrophotometry
Source Info: U.S.EPA National Exposure Research Laboratory (NERL)
Microbiological and Chemical Exposure Assessment Research Division (MCEARD)
[formerly the Environmental Monitoring Systems Laboratory (EMSL), Cincinnati, OH]
26 West Martin Luther King Drive
Cincinnati, Ohio 45268-0001
Fax: 513-569-7757
email: DWmethods.help@epa.gov
Citation: Methods for the Chemical Analysis of Water and Wastes (MCAWW) (EPA/600/4-79/020)
11566 Byte file
Brief Method
Summary:
 Arsenic in the sample is reduced to arsine (arsenic trihydride) in acid solution in a hydrogen generator. The arsine is passed through a scrubber to remove sulfide and is absorbed in a solution of silver diethyldithiocarbamate dissolved in pyridine. The absorbance of the red complex that forms is proportional to arsenic concentration and is measured with a spectrophotometer.
Scope And
Application:
 This method determines inorganic arsenic in drinking water and most fresh and saline waters in the absence of high concentrations of chromium, cobalt, copper, mercury, molybdenum, nickel, and silver. Industrial wastes may be analyzed after digestion by EPA Method 206.5.
Applicable
Conc Range:
 Above 10 ug/L.
Interferences: (A) Odor: If pyridine odor is objectionable, 1-Ephedrine in chloroform can be use as a solvent for silver diethyldithiocarbamate.
(B) Nitric acid: Nitric acid can produce a negative interference. Use sulfuric acid as a preservative if only inorganic arsenic is being measured.
For additional interferences see EPA Methods 200.0 and 206.5.
QC Requirements: Spike industrial waste samples with a known amount of arsenic to establish adequate recovery. QC requirements for drinking water procedures are provided in method 200.0.
Sample Handling: Use an air-tight system to avoid loss of arsenic during arsine evolution. Additional procedures are provided in EPA Method 206.5 and 200.0.
Max Holding Time:
 6 months (MCAWW, Table 1).
Sample Prep Met 200.0, 206.5
Relative Cost: Less than $50
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