Extraction solvents?

Question

If I wanted to extract a compound which was dissolved in a mixture that contained both water and ethanol, what would be the best solvent to use? Am I correct in assuming that I need something which is not miscible with either water or ethanol? And might this be a problem as ethanol is miscible with polar and non-polar solvents?

Thanks

Answer 1

I'm not experienced with solvent extraction, beyond memories of undergraduate organic labs, but here is what I would suggest:

Do you know if your material was soluble in water only?

I would try extracting with a nonpolar solvent such as toluene. if you believe your material would go into the organic phase, it is also a good idea to add salt to the aqueous phase (Safety note - benzene should no longer be used for this sort of thing because of toxicity). In the unlikely event that the toluene dissolves in the mixed water-ethanol layer, add more water.

Depending on quantities, and on the importance of the extraction, it may be a good idea to experiment with small portions first.

Answer 2

You need to know the solubility of the product that you want to extract. You are right in saying that you can not extract something out of water with ethanol because these two solvents are miscible. Could you posibly isolate the material that you are looking for by recrystalization from a solvent system? To separate with a liquid/liquid system, you need to have a solvent in which the material that you want is soluble and that would not be miscible with EtOH or water.