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

Summary
Analytes
Revisions
Data and Sites

Official Method Name

Method 410.4: The Determination of Chemical oxygen demand by semi-automated colorimetry

Current Revision

Revision 2.0, August 1993

Media

WATER

Instrumentation

Spectroscopy (Colorimetry; Photometry)

Method Subcategory

Inorganic

Method Source

EPA-ORD / EPA-OST

Citation

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 150^oC. 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

3-900

Interferences

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 4^oC 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 4^oC.

Maximum Holding Time

28 days

Relative Cost

Less than $50

Sample Preparation Methods

This method has 1 analyte associated with it.

Analyte	Detection Level	Bias	Precision	Pct False Positive	Pct False Negative	Spiking Level
COD(E-10117) COD Chemical Oxygen Demand	3.000 mg/L	104% Rec (ML)	27.50 % RSD (ML)			18.20 mg/L

Precision Descriptor Notes:	Precision and accuracy values were calculated using interlaboratory data from performance evaluation studies.
Detection Level Note:	MDL is established using reagent water fortified at a concentration of 2 to 3 times the estimated instrument detection limit and is determined from 7 replicate aliquots of the fortified reagent water and processed through the entire analytical method.

Revision	PDF/Link
Revision 2.0, August 1993
Issued 1978

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

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