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Method Performance
Summary of Method
OxygenCOD_Other_Other_MD3_Eng_Ody.fm
3. Touch
. Touch
On
Adjust
concentration is used, touch the number in the box to enter the actual
concentration, then touch
See Section 3.2.4 Adjusting the Standard Curve on page 40 for more information.
Note: Data is for Manganese III COD without the chloride removal procedure.
Precision
Standard: 500 mg/L COD
Program
432
See Section 3.4.3 Precision on page 44 for more information, or if the standard
concentration did not fall within the specified range.
Sensitivity
Portion of Curve
Entire range
See Section 3.4.5 Sensitivity on page 44 for more information.
Chemical Oxygen Demand (COD) is defined as "... a measure of the oxygen
equivalent of the organic matter content of a sample that is susceptible to
oxidation by a strong chemical oxidant" (APHA Standard Methods, 19th ed.,
1995). Trivalent manganese is a strong, non-carcinogenic chemical oxidant that
changes quantitatively from purple to colorless when it reacts with organic
matter. It typically oxidizes about 80% of the organic compounds. Studies have
shown that the reactions are highly reproducible and test results correlate closely
to Biochemical Oxygen Demand (BOD) values and hexavalent chromium COD
tests. None of the oxygen demand tests provide 100% oxidation of all organic
compounds.
A calibration is provided which is based on the oxidation of Potassium Acid
Phthalate (KHP). A different response may be seen in analyzing various
wastewaters. The KHP calibration is adequate for most applications. The highest
degree of accuracy is obtained when test results are correlated to a standard
reference method such as BOD or one of the chromium COD methods. Special
waste streams or classes will require a separate calibration to obtain a direct
mg/L COD reading or to generate a correction factor for the precalibrated KHP
response. The sample digestion time can be extended up to four hours for
samples that are difficult to oxidize. Test results are measured at 510 nm.
Oxygen Demand, Chemical
to accept the displayed concentration. If an alternate
. Touch
.
OK
Adjust
95% Confidence Limits of Distribution
479–521 mg/L COD
∆Abs
0.010
∆Concentration
8 mg/L COD
Oxygen Demand, Chemical
Page 7 of 8
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