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Topic: Need help with solvent extraction  (Read 3895 times)

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Offline c0ok1e

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Need help with solvent extraction
« on: October 18, 2009, 02:02:17 AM »
I carried out solvent extraction using acidified water and butanol. After shaking to mix the solution, there is a layer which is not soluble in either the water layer or butanol layer. Is this phenomenon common or is my technique in shaking wrong? Anyone encounter this before? WHat should I do?

Offline c0ok1e

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Re: Need help with solvent extraction
« Reply #1 on: October 18, 2009, 02:38:44 AM »
Another problem is I used ethyl acetate to extract also and then evaporate. After evaporating i keep my extract in fridge. AFter 1 week I wanna resolubilize my extract with ethyl acetate ot doesnt soluble. It suppose to be able to soluble with the solvent right cuz I extract using the same solvent?

Offline KritikalMass

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Re: Need help with solvent extraction
« Reply #2 on: October 18, 2009, 04:14:23 AM »
I carried out solvent extraction using acidified water and butanol. After shaking to mix the solution, there is a layer which is not soluble in either the water layer or butanol layer. Is this phenomenon common or is my technique in shaking wrong? Anyone encounter this before? WHat should I do?

What isomer of butanol did you use? To me it sounds like you formed an emulsion. There is a section on them here with some videos on how you can try to fix them or make them less worse
http://www.uwplatt.edu/chemep/chem/chemscape/LABDOCS/catofp/mixpour/sepfunl/sepfunl.htm

Offline c0ok1e

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Re: Need help with solvent extraction
« Reply #3 on: October 18, 2009, 05:04:43 AM »
I use n-butanol. Im not sure if its emulsion. The unsoluble layer partition between the water and butanol later making it 3 layers.

How about my second question regarding resolubilizing the ethyl acetate layer? It suppose to be able to resolubilize right? Or is it wrong to store it in fridge before this?

Offline Arctic-Nation

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Re: Need help with solvent extraction
« Reply #4 on: October 18, 2009, 01:16:00 PM »
Resolubilizing isn't always as simple as it seems. That a certain solvent can extract a compound from a reaction mixture doesn't necessarily mean that it will be able to solubilize it from the solid state. I've done extractions of carboxylic acids using EtOAc, but after evaporation these things wouldn't go into solution again unless using forcing conditions (heating, magic mixtures).

Kathy-Barnes

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Re: Need help with solvent extraction
« Reply #5 on: October 18, 2009, 04:13:05 PM »
What was the temperature of mixing?

Perhaps, it needs to be warmer to get a good solution and to avoid the emusification.

Offline c0ok1e

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Re: Need help with solvent extraction
« Reply #6 on: October 18, 2009, 11:55:10 PM »
I do them in room temperature.. If resoluzilizing if difficult how do i get them out of my flask? Cuz they stick to the wall. Can DMSO work to soluble organic compounds? Please teach  :'(

Offline KritikalMass

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Re: Need help with solvent extraction
« Reply #7 on: October 19, 2009, 12:50:02 AM »
Whatever solvated the compound I always just throw some more of that in flask and scrape around in there with a spatula. Not alot, just enough to get it unstuck from the walls of the flask or whatever. Now mind you I am not a graduate student and have only had couple semesters of Ochem, but that is what I do. As long as you put that in your write up/report most TAs understand.

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