Science Buddies: "Ask an Expert"

Hello,
I have an issue with the LaMotte Dissolved Oxygen test. I have followed the steps correctly and have performed this test on multiple samples with excellent results. However, with this one container (aeroponics container with multiple airstones and air pumps) I am not able to get the sample to turn blue when I add the starch indicator solution. The test tube remains a pale yellow and does not change to clear or blue. I am not sure why. Is there too much iodine? Too much oxygen? The starch indicator solution has no effect. Are you able to help me understand what is happening? It only effects the water sample from one aeroponics container (with a high amount of oxygen being pumped into the container). The other water samples from regular hydroponics containers are able to be measured using the LaMotte Dissolved Oxygen kit with no issue.

Hello JSunshine,

Do you mind taking a step back and explaining the question you're trying to address, the hypothesis you're testing, and the experimental procedure you came up with to test this hypothesis? What are you measuring with this LaMotte dissolved oxygen kit and why? If you give us a little more detail, we can better help you troubleshoot what might have gone wrong with this one sample of yours. I would also suggest posting this question to the physical sciences thread because there could be some chemists there that may potentially know what could've gone wrong.

Best,
Connie