[Kaladiscope]

Here comes the question:

Which are the solvents most frequently used for column chromatography?

As far as I know ethyl acetate and tiny amounts of methanol are one of the most commonly mixture used to separate different compounds (in this case specifically compounds which are not really polar).

Do u know which are the most favorite ones to perform a column?

Thanks!

[fledarmus]

I almost always use either methanol/dichloromethane or ethyl acetate/hexane on silica columns, depending on the polarity and solubility of my products.

[Doc Oc]

I almost always use either methanol/dichloromethane or ethyl acetate/hexane on silica columns, depending on the polarity and solubility of my products.

Ditto, though I default to hexane/ethyl acetate and only use DCM/MeOH for real sticky stuff like amino acids.

[Kaladiscope]

Regarding methanol in columns, until which % of this solvent do u work?

I mean, knowing that methanol dissolve silica, in my case I work always until 10 %, and even though I have always found some silica particles in my product (filtering the compound I can get rid of the silica).

[fledarmus]

I haven't had any problems going up to 20% regularly, and if I get something really polar I sometimes push to 25%. I haven't had any noticeable issues in a while, but that depends some on the manufacturer of the silica gel; one of the brands I used some 15 years ago would give significant silica gel solution every time at 25%.

[stewie griffin]

My go to is ethyl acetate/hexanes. For more polar I will go to DCM/MeOH. I try to stay below 10% MeOH but I have gone up to about 20% when desperate.
Sometimes I also add NEt₃ to help deactivate the silica gel if I need.

[Nescafe]

DCM/MeOH and Ethyl acetate/Hexanes are the most conventional. However, depending on what sort of functionality you are dealing with you can use "smart" solvent mixtures. Lets say you have an acidic functionality, sometimes a mixture of DCM(97%)/MeOH(2%)/AcOH(1%) can ensure that the acid functionality is in its protonated form and in a way simplify the purification. With amines a small amount of ammonium hydroxide could be introduced in the MeOH/DCM mix. MeOH, DCM and water based systems can also do wonders for purifying very polar compounds.

Hope this helps!

Nescafe.

[Dan]

Normally I will use EtOAc/Hexane. If that does not separate the mixture effectively, I will try other combinations:

Strong solvents: EtOAc, acetone, diethyl ether
Weak solvents: Hexane, toluene, DCM, CHCl₃

This week I've run columns in acetone/hexane, EtOAc/chloroform, EtOAc/Toluene, and EtOAc/hexane. The project I'm working on generates products that tend to co-elute with the starting material in most solvent systems, so I have to get creative.

[Babcock_Hall]

Doc Oc,

What percentage of methanol, and which amino acids?  We make amino acid derivatives in my lab, but I was under the impression that they were too polar for silica.

[Doc Oc]

Depends on the aa, and how the sidechain behaves/is protected.  I should add that I don't run columns if the amine isn't protected, those can generally be precipitated as the HCl salt.  For something like N-Boc serine, I've used 10% MeOH and been able to get the acid out.  I should also add the TLC spots aren't nice looking tight circles, a lot of times they smear and streak.  But they're usually easy to get away from other junk you've used in the reaction so you can still get good yields.