Can a dissolved oxygen sample be preserved for later analysis?

Document ID

Document ID TE273

Published Date

Published Date 27/05/2017
Question
Can a dissolved oxygen sample be preserved for later analysis?
Summary
Sample preservation for Winkler dissolved oxygen method
Answer
The Hach LDO probe is a simple way to quickly measure dissolved oxygen without reagents, titrations, membranes or polarization time.  Samples can be measured immediately in your process without the need for transport to a lab or preservation.

However, dissolved Oxygen samples for Winkler titration can be preserved for up to 8 hours by following these steps:
1. Collect samples in a clean BOD bottle as described in the procedure.
2. Add the first 2 reagents (manganous sulfate and alkaline iodide-azide, or Dissolved Oxygen 1 and 2).
3. Immediately insert the stopper and mix well.
4.Store in the dark at the temperature of the water source, or seal with water and store in the dark at 10-20°C. To seal with water: Pour a small amount of water around the stopper. Place a BOD bottle cap (catalog number 241906 for 300 mL BOD bottle) over the top of the bottle and push until it snaps in place. After storage, start the procedure at addition of sulfamic acid (or Dissolved Oxygen 3) reagent, and titrate the sample.