Vacuum Liquid Chromatography (VLC) Solvent Systems

Discussions about HPLC, CE, TLC, SFC, and other "liquid phase" separation techniques.

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Hello!

I am currently working on different solvent systems for VLC for plant samples. The property that I am focusing on is polarity (since this is the basis for VLC). The solvent system that is commonly used in the lab that I am working on involves hexane and ethyl acetate (polarity index of 0.0 and 4.4, respectively). I have also read that solvents with aromatic groups such as benzene and toluene are toxic, same for halogenated ones such as dichloromethane and chloroform. Other solvents are also volatile such as ethers and pet ether. I have also read on green solvents (such as Me-THF, CPME, etc) and thought of using them but I have not seen actual studies that used these for any kind of chromatography. Also, I am not sure if I can use solvents of one kind of chromatography to another, say flash chromatography solvents to VLC.

tl;dr: It's hard to look for VLC solvent systems. I wish to know what other systems I can use aside from aromatic and halogen-containing ones, and if I can also use green solvents. Lastly, can I translate one solvent system of chrom to another?

Thank you, I hope someone reads this. :)
As far as the chrmatography goes, what you are doing is liquid-solid adsorption, just as it would be in thin-layer or open-column gravity flow, so any solvents used in those techniques should be applicable.

As far as safety/toxicity are concerned, so long as you work in a hood and take standard precautions, there should be no problem (for what it's worth, I'm old enough to remember rinsing my hands with acetone to remove residual organics -- this in the late 60's).

As far as "transferring" mobile phases from one type of system to another goes, it's feasible to a limited extent: you can match polarity (approximately), but the exact elution strength and selectivity will depend on the silica gel (things like pore size, surface area, acidity, etc.), so that going from one source of silica to another will probably involve "tweaking" the mobile phase composition. One good way to check is to use the same silica on a TLC plate and develop the plate in your proposed mobile phase. That should give you an approximate idea of how it will behave under VLC.
-- Tom Jupille
LC Resources / Separation Science Associates
tjupille@lcresources.com
+ 1 (925) 297-5374
tom jupille wrote:
As far as the chrmatography goes, what you are doing is liquid-solid adsorption, just as it would be in thin-layer or open-column gravity flow, so any solvents used in those techniques should be applicable.

As far as safety/toxicity are concerned, so long as you work in a hood and take standard precautions, there should be no problem (for what it's worth, I'm old enough to remember rinsing my hands with acetone to remove residual organics -- this in the late 60's).

As far as "transferring" mobile phases from one type of system to another goes, it's feasible to a limited extent: you can match polarity (approximately), but the exact elution strength and selectivity will depend on the silica gel (things like pore size, surface area, acidity, etc.), so that going from one source of silica to another will probably involve "tweaking" the mobile phase composition. One good way to check is to use the same silica on a TLC plate and develop the plate in your proposed mobile phase. That should give you an approximate idea of how it will behave under VLC.


Hello, thanks for replying and sorry for the late response. I really appreciate your answer as I am still stuck with my study ahaha

Our lab upgraded by adding hoods in the rotavap area so I am no longer limited with toxic chemicals but it is still better for me to use safer alternatives.

I see. Do you have a good reference in mind where I can read more on these properties that affect the "transferring"? I think I need to go back to the fundamentals of chemistry to appreciate all of these ahaha
The "go to" reference is Snyder's "Principles of Adsorption Chromatography" book from 1986 (yes, this has been around for a long time!). I found one used copy available on Amazon:
https://www.amazon.com/Principles-Adsor ... ref=sr_1_1
-- Tom Jupille
LC Resources / Separation Science Associates
tjupille@lcresources.com
+ 1 (925) 297-5374
tom jupille wrote:
The "go to" reference is Snyder's "Principles of Adsorption Chromatography" book from 1986 (yes, this has been around for a long time!). I found one used copy available on Amazon:
https://www.amazon.com/Principles-Adsor ... ref=sr_1_1


Thank you very much! ♥
Vacuum liquid chromatography (more often called Dry Column Vacuum Chromatography) is almost all the columning I've ever used in the organic lab. The three solvent systems that has covered 99% of what I've done has been
ethyl acetate:heptane
dichloromethane:heptane
dichloromethane:toluene

So much can be done with gradient/fraction volume control that very precisely tailored solvent systems often are unnecessary.
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