Dear Serkan Koldaş ,

As I understand your situation, you perform a liquid/liquid partition of an extract in order to realize a bio-guided fractionnation right ?

When you do that, you shouldn't look at the color of your solution, because many compounds are colored. The purpose is to split the compounds in a solvent who they have a good affinity. If you use salt in order to dephase quicker, you will maybe lost or dissolve compounds in a solvent where they shouldn't be.

Moreover, you will need to remove the salts from your aqueous phase in order to calculate the yield of extraction, which is not that easy !

When I perform a liq/liq partition, if my solution is mixed I try to add just a little bit of pure ethanol (it can help bi changing just a little bit the polarity) but don't add to much because you'll create one phase.

My other solution (my preferred one) is to centrifuge all my fractions, which is time consuming, but extremely efficient.

My last advice, don't think about color but in compounds, follow your partition by TLC, and you'll see the compounds who are extracted and when to stop with a solvent and begin the next one.

Good luck with your work !

Best regards,

Dear Maël Gainche,

thanks for your comments.

Actually, I am not doing a bio-guided fractination. I am just traying to separate the molecules in the crude extract based on their polarity by means of liq-liq extraction. And at the next step, I will work on these organic phases, not the water phase.

And yes, color is not a certain indicator to when to finish the extraction.

As we know, BuOH has a solubitiy in water, and vice versa. My above mentioned experiment (before saline addition, BuOH phase's color was yelowish; after saline addition, it was colorless) might show that the color would be caused from the water which is dissolved in BuOH, I mean some of water-soluble molecules might be carried into BuOH phase by that small amount water which is dissolved in BuOH.

My question or curiosity is;

- Is it possible by adding some NaCl into the water phase we can eliminate the water-soluble molecules (not soluble/extractable/partitionable in/into BuOH alone) to enter to the BuOH phase, and even not deal with unnecessary compounds? Because NaCl will prevent water molecules to go into the organic phase, as NaCl is a more prefered compound than BuOH (polar-ionic interaction; similar likes similar).

-And again, by adding some NaCl into the water phase can we increase the yield, because water will be saturated with ions and organic molecules which have slight affinity to water molecule will be free and go into the organic phase?

Oh ok I misunderstand your problem.

Well I never have this kind of situation in my work. Effectively, BuOH is moderately soluble with water, and thats a problem in your case. But if you add lots of NaCl, you'll maybe put some in your BuOH phase with water ? I'm not sure that you'll not have any water in your BuOH fraction, and tha could be a problem...

Maybe you could try first to add some BuOH and some water with NaCl, shake those two ones and split your phase. Then evaporate your BuOH fraction, and watch the formation of precipitate, or if you evaporate something at 75mbar at 40°C. Last solution, if you have Karl Fischer, try an analysis on you BuOH fraction.

Generally, I never add a perfect separation of compounds between my water and my BuOH fraction, compounds can be found in both...

I'm curious about the results of some tests now !

Good luck !

Best regards,