Oxygen Demand, Chemical
Oxygen Demand, Chemical
Page 4 of 8
OxygenCOD_Other_Other_MD3_Eng_Ody.fm
• To avoid cross-contamination between samples, clean forcep tips between samples by wiping with a clean towel or rinsing with
deionized water.
• If the sample does not contain suspended solids, it is not necessary to transfer the filter to the digestion vial.
• 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.
• To oxidize resistant organics, you can digest samples for up to four hours. Digest the blank for the same time period as the
samples.
5. Pipet 0.60 mL of
acidified sample (see
Preparing the Acidified
Sample on page 1) into the
CRC. Pipet 0.6 mL of
acidified blank into
another CRC. It should
take 30–45 seconds to
draw the liquid through
the CRC into each vial.
6. Close the vacuum
regulator valve
completely to achieve full
vacuum. After one
minute of full vacuum,
slide the VPD back and
forth several times to
dislodge any drops
clinging to the cartridge.
7. Open the VPD
regulator valve to release
the vacuum. Turn the
pump off. Remove the
VPD top and set it beside
the base.
8. Proceed to Tips and
Techniques for Sample
Preparation and
Measurement.
1. Use forceps to
remove the filter from the
top of each CRC.
2. Place each filter in the
corresponding Mn III
COD Vial. (Use numbers
on the VPD as a guide.)
3. Remove the Mn III
COD vial from the
vacuum chamber and
replace the original cap.
Screw the cap on tightly.
4. Invert the vials
several times to mix.
See
Below
Tips and Techniques for Sample Preparation and Measurement
Sample Preparation and Measurement
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