[Scintillation]

Hi all!

Can a flash chromatography column (packed with normal silica) be washed with a polar solvent (e.g. iPrOH or acetone) and be reused several times without affecting the performance? Of course, I'm talking about a situation where the silica would look clean (white) after washing it.

I'm asking this because I had the chance to use an automated column chromatography machine which employs reusable columns. Since we have no money for this device, I though just washing my columns would make me save a lot of time, especially for small ones because the column packing is a big part of the whole process.

If you have references about that, please tell me!

Thanks

S.

[Doc Oc]

My thoughts on this:

1) Yes, it can be regenerated, although I've never done it because

2) Silica isn't that expensive.  I've only known a couple of labs that re-used their silica, and it was either because they had no money or the PIs were super stingy.

3) Packing a column shouldn't be a significant part of the whole effort, it should take about 10 minutes.

So in a nutshell, I don't see the value in recycling your silica unless your lab can't afford to buy more of it.

[azmanam]

We got a free automated column runner my last year in grad school.  it came with a finite amount of pre-packed columns, and we wanted to get the most out of them we could.

Filter your crude reaction mixture through a short silica plug FIRST before loading it on the auto column.  This will filter out baseline junk that will clog and eventually ruin your auto columns.  Then, be sure to flush with several column volumes of polar solvent at the end, and equilibrate with a few column volumes of your eluent to flush the polar solvent out.

This worked well enough for us.

[nox]

Hmmm, interesting question.

I suppose I can see the value in recycling flash columns when you're doing scope expansion and need to clean up a library of molecules made on a similar scale.

[Scintillation]

Thank you guys for your comments!

Actually, a 10 min preparation is a big part of the process in my case. The separations I do on a 50 mg scale generally take 10-15 min total (including evaporation of fractions).

However, this will require more solvent to wash and re-equilibrate, so I'm not sure we're really gonna save money.

[fledarmus]

If you account for the solvent and especially solvent disposal costs as well as the time required, there isn't much point to reusing silica gel columns. Especially since the way you know that it's no longer good is when you ruin a purification. However, academic labs rarely account for solvent disposal costs or time required.

Pre-filtering through a plug of the same column material and carefully maintaining the columns stored vertically, filled with your non-polar solvent and sealed, will help reusability. Although it is almost never done anymore with silica gel, it is fairly common with more expensive columns such as C-18 (except it is stored in the polar solvent) or (*gasp!*) chiral columns.

[Doc Oc]

I agree that the cost savings will be negligible at such a small scale.  I've heard of people recycling silica after purifying 10 g of material, that's a large amount of silica.  On a 50 mg scale, I could comfortably throw that out and not lose sleep.