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DR/2400
Method 10067
Scope and Application:
* U.S. Patent 5,556,787
Tips and Techniques for Preparing the Acidified Sample
• Use this method if the sample contains chloride. To determine if the sample contains chloride, use Quantab
range chloride (Cat. No. 27449-40).
• If the sample COD is expected to exceed 1000 mg/L, dilute the sample as described inTable 1 on page 2.
• Blending the sample promotes even distribution of solids and improves accuracy and reliability.
• Run one blank with each lot of reagent. Run all samples and blanks with the same lot of vials. The lot number appears on the
container label.
• The stability of the reagent blank allows for reuse. Verify the reagent blank quality by measuring the absorbance of the blank vs. a
clean COD vial filled with deionized water. The absorbance range should be about 1.41–1.47.
• If the sample boils during the digestion, the vial is not properly sealed. Test results will be invalid.
• Place a safety shield in front of the COD reactor to prevent injury if splattering occurs.
• Spilled reagent will affect test accuracy and is hazardous. Do not run tests with spilled vials.
Preparing the Acidified Sample
1.
Turn on the COD
Reactor and heat to
150 °C. Place the safety
shield in front of the
reactor.
OxygenCOD_Other_Other_MD3_Eng_Ody.fm
For water and wastewater
2.
Homogenize 100 mL
of sample for 30 seconds
in a blender.
If suspended solids are
present, continue to mix
the sample while
pipetting.
Oxygen Demand, Chemical
Manganese III Reactor Digestion Method
(with optional chloride removal)*
3.
Pipet 9.0 mL of
homogenized sample
into an empty glass
mixing cell (the prepared
sample) and 9.0 mL of
deionized water into
another empty glass
mixing cell (the blank).
(30 to 1000 mg/L COD Mn)
®
Titrator Strips for low
Note: Mixing concentrated
sulfuric acid and water is not
additive. Adding 1.0 mL of
concentrated sulfuric acid to
9.0 mL of sample does not
result in a final volume of
10.0 mL. This factor is built into
the calibration curve.
Oxygen Demand, Chemical
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