soma
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determining chromatography column size
I want to purify about 25 gms of product by chromatography. One book says to use a column that is about 2.3" diameter x 23" inches height. The amount
of silica would be 1250 gms -- (50 x product weight). They give a graph to find the column size for the amount of silica. It shows for 1200 gms silica
- 6 cm diameter and 60 cm height column.
Comments?
[Edited on 26-8-2016 by soma]
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NEMO-Chemistry
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Seems like alot of solvent as well, I would guess HPLC is the goto but pricey.
So column wise can you do it with a smaller column and do it in stages after recycling the solvent, obviously your risking contamination etc but
depends how much money your willing to spend versus how pure you need it.
Ignore most of it i just like having a try at answering 
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brubei
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that's a pretty huge column. Does your product really worth it ?
Is crystallisation totally ineffective ?
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Metacelsus
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25 grams is a lot to purify by chromatography (I rarely run columns on anything over 5 grams). I would investigate recrystallization or vacuum
distllation first. If you must do chromatography, your required column size will depend on the impurities you are trying to remove (how similar they
are in retention factor). However, at minimum I would suggest a column with a void volume of 250 mL (10 mL per gram has worked well for me). I don't
know the exact properties of your stationary phase, but if it occupies roughly 50% of your column volume, that means you'll need a total column volume
of at least 500 mL. Again, if your impurities have similar retention, this will need to be much larger.
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NEMO-Chemistry
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Quote: Originally posted by Metacelsus  | | 25 grams is a lot to purify by chromatography (I rarely run columns on anything over 5 grams). I would investigate recrystallization or vacuum
distllation first. If you must do chromatography, your required column size will depend on the impurities you are trying to remove (how similar they
are in retention factor). However, at minimum I would suggest a column with a void volume of 250 mL (10 mL per gram has worked well for me). I don't
know the exact properties of your stationary phase, but if it occupies roughly 50% of your column volume, that means you'll need a total column volume
of at least 500 mL. Again, if your impurities have similar retention, this will need to be much larger. |
Thats alot less than i imagined, i guess if you can reclaim the solvent then it isnt a bad option. 10ml per gram is something i will stick in my
memory, thanks for that as well as the void and total length.
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Metacelsus
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Let me emphasize that in my experience this is a minimum amount, and in many cases much more than this will be required.
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