dissolved oxygen

Question

Two samples were collected simultaneously at the same spot in a river for dissolved oxygen analysis. One sample was fixed immediately after collection, and the other was treated later in the laboratory. Indicate two possible factors that could cause lower results to be obtained in the second sample.

Answer 1

Hello, Ecem,

I'll take a few wild guesses and you can pick the serious ones:

1. The dissolved oxygen is released into the airspace above the water sample. (most likely answer)
2. The dissolved oxygen reacts with impurities in the water or with the vessel in which it is stored.
3. Your lab assistant drank a portion.

Bob