When we started the experiment at first at 1ppm all the fishes died within 12 hours. repeated the experiments with lower concentrations starting from 0.05 ppm and found a very good response to the test results. But when repeated mortality is not reported at even 1 ppm till 96 hours. At 2 ppm 100% mortality was reported twice within 72 hours again when repeated once more only 20% mortality was reported at the end of 96hrs. What could be the possible reson for that?
p.s: I tried using a newly bought chemical.
There are several factors that could lead to inaccurate or improper results in an acute toxicity test. Some potential reasons include:
1. Inaccurate dosing: If the test subjects are not receiving the correct dosage of the substance being tested, it can skew the results.
2. Variability in test subjects: Differences in age, sex, weight, genetics, or overall health of the test subjects can affect how they respond to the substance being tested.
3. Environmental factors: Conditions such as temperature, humidity, or lighting in the test environment can impact the results of the test.
4. Contamination: If the test substance or the test samples become contaminated during the testing process, it can affect the results.
5. Testing procedures: Errors or inconsistencies in the way the test is conducted can lead to unreliable results.
6. Interference from other substances: Presence of other substances in the test environment that could interact with the test substance and affect the results.
It is essential to carefully review all aspects of the test methodology to identify any potential factors that may be contributing to the improper results. Adjustments to the testing procedures or conditions may be necessary to ensure accurate and reliable results.
How many repetitions (= parallel series of all dosages) did you have?
I have done 3 repetitions for all the concentrations.
In one I have got the results.
I don't undertand: which results? If one series is showing weird outcomes, but the rest is ok, I'd just do it again, because the outlyer was obviously just that: an outlyer.
Sir, at the very beginning I used 1ppm arbitrarily to get the probable concentrations for 96hr lc50 test. At 1 ppm all I found 100% mortality within 20 hrs. And I again started with very low concentrations starting from 0.05 ppm. From 0.05 - 0.3 ppm I found no mortality. But after that from 0.4 ppm - 0.7 ppm I found 33% and 66% mortality (I used 3 fishes for this). Again I tried the same range of concentrations 0.6 ppm and 0.7 ppm using 5 fishes and found 40% mortality in 0.6 ppm and 30% mortality in 0.7 ppm. So continued the repetitions after that. But unfortunately this time I have found no mortality even at 1 ppm as well. But at 2 ppm I found 33% mortality in 96 hrs. I am currently working with higher concentrations i.e 2 ppm and 3 ppm.
Based on the review of literature for the chemical I am using most of the paper reported concentrations below 2/3 ppm to be toxic for small fishes.
I again purchased the chemical thinking that the chemical might have expired or contaminated but it is showing no differences.
One uses usually 10 individuals per concentration. When you test 5 concentrations that is 1+5 = 6. = 60 fish
See also OECD Guideline on Fish Trials https://read.oecd-ilibrary.org/environment/test-no-203-fish-acute-toxicity-test_9789264069961-en#page14
This forum is not appropriate for detailed exchanges, so if you wish, you can contact me at [email protected]. I'll answer during office hours.
Thank you so much for your answer.
I will drop you a mail for further discussion.
- Badges
- Science topic
- Similar topics
- Chemistry
- Biochemistry