optragon - 23-3-2016 at 07:59
To wash or not to wash?
I couldn't find this information anywhere... So when partitioning an aqueous solution in a liquid-liquid extraction between different organic
solvents, I usually wash and dry them over MgSO4. With BuOH, I usually wash in it a saturated NaCl solution, but the aqueous phase seems to absorb a
lot of colour coming from the BuOH phase, which doesn't usually happen with other solvents. I wonder what is considered the best practice in this case
- wash or not?
Thanks for input!
[Edited on 23-3-2016 by optragon]
brubei - 23-3-2016 at 08:17
if you get satisfied by not washing it while using BuOH, why doing it with other solvent ?
You'll have to think about how to remove impurities by other process or your choose of solvent is probably bad.
chemrox - 23-3-2016 at 10:43
It's really hard to sort this out without knowing what you're extracting. If the colored matter is what's to be left behind then use another solvent.
If the molecule you wish to keep is an amine then washing with base is a good idea followed by a salt wash. DCM works for a lot of material. Is the
color coming from some sort of pill? (I can't fucking believe "amine" isn't in the dictionary). Have you tried activated charcoal to de-colorize the
organic layer?
optragon - 24-3-2016 at 01:38
I'm extracting Rhodiola rosea and butanol cannot be substituted, it follows an EtOAc extraction. I'm not sure if the colored matter is important, but
I'd ideally like to keep it in the butanol. But the problem is that the butanol layer is quite contaminated by smeary precipitates from the aqueous
extract, so it needs to be cleaned somehow. Filtration doesn't work, it passes through. Washing over NaCl works, but as said ideally I'd like to not
remove anything more than necessary. So the question is really how to remove the contamination from the butanol without a water wash?
Tsjerk - 24-3-2016 at 01:47
Use a better filter, a glass filter for example.
optragon - 24-3-2016 at 06:43
Good idea. I'll check with different filters.