I am currently doing the daphnia acute immobilisation test and am trying to find out why our negative controls are fine after 24 h, but immobilised after 48 h. O2 levels and pH do not seem to be the problem. Has anyone experienced similar problems?
All exposure vessels have been thoroughly cleaned, so contamination seems unlikely.
Thanks in advance for any ideas!
I have never had this problem. Maybe, dilution water is the problem. What type of water do you use? For example, surface or ground water, reconstituted water or dechlorinated tap water are acceptable as dilution water.
I use the ISO test water (prepared with Milli-Q water) that is mentioned in the OECD guideline and aerate it over night. So I really don't understand what could be wrong anymore.
In my experience, dechlorinated tap water is the best option (even if you want carry out the chronic toxicity test). When I used reconstituted water, always had a problem.
Do you protect your vessels during the test? Your problem might be some volatile compound (organic sovent, contamination in your BOD).
I agree with Monike opinion. I think your breeding vessels should be new and should not have been used for another job before.
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