How can I avoid getting an air bubble in the bottle when following the Winkler titration method for dissolved oxygen?

Document ID

Document ID TE271

Published Date

Published Date 27/05/2017
Question
How can I avoid getting an air bubble in the bottle when following the Winkler titration method for dissolved oxygen?
Summary
How to avoid trapping air bubbles in a winkler titration
Answer
Air may become trapped in the bottle when replacing the stopper after adding reagents. If there is an air bubble in the bottle the dissolved oxygen measurement will be inaccurate and show a higher than actual concentration. Try dropping the stopper from a height of 2 to 3 inches above the bottle, or insert the stopper with a quick thrust to avoid trapping air.