I want to do the following
1. Prepare a stock solution for Gramoxone pesticide (it is labelled 276g paraquat dichloride/L).
2. How do I determine the concentrations to be used in a fish toxicity experiment?
Can anyone help?
To prepare stock solution, just dissolve the stated weight of chemical in one litre of water.
If you want to determine the concentration that will be toxic to fish, you will need to prepare graded solutions from the stock solution to carry out the experiment.
For example, if you want to get 5mg of the chemical, you measure 5ml from the stock and make it up to one litre with distilled water. That's add 995ml of water to 5ml of stock to get 5mg/l of chemical. You can do for 10mg/l, 15mg/l and so on.
But note that you have to do Range Finding test first before the actual experiment to determine the range of concentration to be used for toxicity test.
The common toxicity test is LC50, that's, the concentration of chemical that will cause 50% kill of the experimental animal.
I hope this helps.
Good luck!
According to the MSDS for Gramoxone, the 96-h LC50 for paraquat-dichloride for rainbow trout is 55 mg/L, so multiplied by 1000/276 gives you the approximate LC50 for the formulated product. For bluegill sunfish the LC50 for paraquat-dichloride is 13 mg/L. So, if it is necessary to repeat this vertebrate testing, you would want to space your concentration around the LC50. For aspects of test design you can use the OECD Test guideline 203 acute fish.
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