EPA-ORD / EPA-OST: 410.4:  Chemical oxygen demand in water by colorimetry

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Official Method Name
Method 410.4: The Determination of Chemical oxygen demand by semi-automated colorimetry
Current Revision
Revision 2.0, August 1993
Spectroscopy (Colorimetry; Photometry)
Method Subcategory
Method Source
Method 410.4: The Determination of Chemical Oxygen Demand by Semi-Automated Colorimetry. Edited by James W. O'Dell. Revision 2.0, August, 1993
Brief Method Summary
Sample, blanks, and standards in sealed tubes are heated in an oven or block digestor in the presence of dichromate at 150oC. After two hours, the tubes are removed from the oven or digester, cooled, and measured spectrophotometrically at 600 nm. The colorimetric determination may also be performed manuall.
Reduced volume versions of this method that use the same reagents and molar ratios are acceptable provided they meet the quality control and performance requirements stated in the method.
Scope and Application
This method covers the determination of chemical oxygen demand (COD) in ground and surface waters, domestic and industrial wastes.
Applicable Concentration Range
Chlorides are quantitatively oxidized by dichromate and represent a positive interference. Mecuric sulfate is added to the digestion tubes to complex the chlorides.
Method interferences may be caused by contaminants in the reagent water, reagents, glassware, and other sample processing apparatus that bias analyte response.
Quality Control Requirements
Demonstration of laboratory capability, and periodic analysis of laboratory reagent blanks, fortified blanks, and other laboratory solutions as a continuing check on performance.
Sample Handling
Samples should be collected in plastic or glass bottles. All bottles must be thoroughly cleansed and rinsed with reagent water.
Samples must be preserved with H2SO4 to a pH < 2 and cooled to a 4oC at the time of collection.
Samples should be analyzed as soon as possible after collection. If storage is required, preserved samples should be maintained at 4oC.
Maximum Holding Time
28 days
Relative Cost
Less than $50
Sample Preparation Methods