NEMI Method Summary

Method Summary Information

Method Number: I-2371 Media: WATER
Revision: 1985
Method Source: U.S. Geological Survey (USGS)
Subcategory: INORGANIC Analytes in this method
Official Name: Iodide, colorimetric, ceric-arsenious oxidation, automated-segmented flow
Descriptive Name Iodide, dissolved in water by colorimetry
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
213421 Byte file
Brief Method
Summary:
 The method is based on the catalytic effect of iodide on the ceric-arsenious oxidation reaction in acid solution. In the presence of a small amount of iodide, the reaction follows first-order reaction-rate kinetics and at a given temperature and for a given reaction time, the extent of reduction of ceric- ion is directly proportional to the iodide concentration. Photometric measurement of the absorbance of the solution permits evaluation of the extent of the reaction (Mitchell, 1966).
Scope And
Application:
 This method may be used to determine iodide in fresh water and brines containing from 0.001 to 0.060 mg/L of iodide. Greater concentrations need to be reduced by dilution; however, samples containing concentrations greater than 1 mg/L need to be analyzed by the bromine oxidation method (method I-1370).
Applicable
Conc Range:
 0.001 to 0.060 mg/L
Interferences: Most substances normally present in natural water do not interfere. Bromide ion does not interfere. Low iodide values will be obtained if the pH of the water samples is less than 3 or if the iron concentration exceeds 500 ug/L.
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
Sample Handling: Container Description: 250 mL Polyethylene bottle
Treatment and Preservation: Filter through 0.45-um filter; using filtered sample to rinse containers; container size dependent on laboratory schedule.
Max Holding Time:
 180 days
 
Relative Cost: Unknown
5661
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