Hi, I am preparing organic solvent extracts using cell free supernatent or spent medium using separating funnel. For the same, I took spent medium and organic solvent in 1:1 proportion but somehow acetone:water, ethanol:water and methanol:water is not getting separated in separating funnel. In other words, I am not getting expected solvent layer. How to deal with this problem. Please help. Thank you.
Dear Sandesh S Mandavkar,
Acetone, ethanol and methanol are polar solvents that are mixed with water. There is no way that these mixtures (acetone:water, ethanol:water and methanol:water) can be separated into two layers.
The best way to solve this problem (may be partially or fully) is to add a third solvent such as dichloromethane (DCM) to the the mixtures. It is expected that a large portion of the polar solvent will be partitioning into the dichloromethane. The result is that you get two layers: the water layer and DCM layer containing the polar solvent. If you make 3-4 times extraction with DCM you may succeed to get a significant portion of the polar solvent into DCM. Alternatively, you can replace DCM with diethyl ether or do the procedure twice one with DCM and the other with diethyl ether. By doing so you can increase your chances to remove the polar solvent from the water layer into DCM or diethyl ether.
Hoping this will be helpful,
Rafik
Dear Sandesh S Mandavkar,
Acetone, ethanol and methanol are polar solvents that are mixed with water. There is no way that these mixtures (acetone:water, ethanol:water and methanol:water) can be separated into two layers.
The best way to solve this problem (may be partially or fully) is to add a third solvent such as dichloromethane (DCM) to the the mixtures. It is expected that a large portion of the polar solvent will be partitioning into the dichloromethane. The result is that you get two layers: the water layer and DCM layer containing the polar solvent. If you make 3-4 times extraction with DCM you may succeed to get a significant portion of the polar solvent into DCM. Alternatively, you can replace DCM with diethyl ether or do the procedure twice one with DCM and the other with diethyl ether. By doing so you can increase your chances to remove the polar solvent from the water layer into DCM or diethyl ether.
Hoping this will be helpful,
Rafik
Rafik is correct - all three of those solvents are completely miscible with water nd so even adding a third solvent is unlikely to solve your problem.
If acetone, ethanol and methanol separately mixed with water, you can separate the polar solvent by collecting the distillate using a Leighbig condenser
If you still have those solutions and you still need extracts, you could try to evaporate as much acetone/methanol/ethanol usind rotary evaporator, and then try extraction with less polar solvent as suggested (dichloromethane, diethyl ether, ethyl acetate...). It is the most basic piece of equipement in any organic chemistry lab, so you could ask around if there is chemistry lab. You will have to evaporate those organic solvents in the end, so you may need it anyway.
Distillation could be of help to separate aqueous and organic solvent.
https://www.researchgate.net/post/How_do_I_fractionate_acetone_extract_from_water_when_no_separation_is_seen_in_a_separating_funnel/1
few hints about acetone:water
Hello,
Thank you so much for such quick reply. But would i be able to get compound solubalised in acetone? Awaiting reply.
You can make the water layer saturated with some salt like NaCl, so that your compound stays in the methanol layer and cannot dissolve in the water layer. then use a separatory funnel to collect the two layers. I assume that your compound is some kind of organics!
Another method: you can just evaporate the whole mixture, do a partition between DMF and water. collect DMF layer, evaporate and dissolve your compound in acetone. all this if your compound is soluble in DMF of course and if you have a good rotary evaporator like heidolph or so!
3rd method: Evaporate everything, methanol and water mixture. refrigerate the dry mixture. use cold methanol or acetone in small amounts (1ml or so ) each time to dissolve small quantities of your compound (tituration). collect in an RB flask and evaporate. try with small quantities, one of these should work for sure!!
Non-volatile or poorly volatile extracts may possibly by separated from the ethanol-water, methanol-water, or acetone-water mixed solvent solution; by either evaporation, vacuum-evaporation, membrane pervaporation, and by drying (e.g. by freeze-drying) (*). Another method could be to separate the solvent mixture by some adequate type of distillation method, possibly vacuum assisted, such as by azeotropic distillation (**). The solute could be possibly recovered either with the bottom or with the distillate. You may also consider to substitute the prior water-miscible solvent by another solvent, either immiscible or poorly miscible with water, so that liquid-liquid phase separation may be considered feasible to extract the extracted solute with the organic solvent layer, possibly assisted by salting-out. In case you want to consider ethyl acetate, you may find useful to check (***).
(*) for freeze-drying, the freezing point of the solvent mixture must be above the freeze-drying temperature; cf. for instance, https://www.researchgate.net/post/Can_using_methanol_damage_a_freeze-drier_machine
(**) you may check binary azeotropes at (e.g.): https://en.wikipedia.org/wiki/Azeotrope_tables
(***) https://www.researchgate.net/post/Dear_all_how_would_you_separate_ethyl_acetate_from_water
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