[MorganFreeman]

Hello,

Recently after talking to a colleague at my graduate school, he mentioned that he runs his flash columns by bringing his compound to a Rf=0.1 and only using 7 cm of silica gel in his column.

When comparing to the paper (http://pubs.acs.org/doi/pdf/10.1021/jo00408a041) by Still, this is not the recommended way. From most people I have talked to they recommend this method.

Anybody have any luck running their flash columns with less silica and a slower solvent system? Also, would there be any advantages to this besides using less silica?

Thanks in advance for any replies.

[Dan]

Different people have different preferred methods. Check this thread for example:

http://www.chemicalforums.com/index.php?topic=50530.0

No one method is wrong. The thing you have to remember about the Still method is that is for moderate resolution. It does not work for difficult separations.

Running a column at lower polarity can improve separation. For example:

http://www.chemicalforums.com/index.php?topic=40724.0

But I find that gradient elution invariably gives better separation, uses less solvent and is quicker than isocratic elution. So I never use the Still method either.

[superg]

Hi,

i did run some column with small size, typically 10cm long (i never go above 30 cm also). this was for very polar compound (eluting with pure ethyl acetate...) and mostly apolar impurities. i washed off yhte impurities first, then eluted my compound.

this is the way i always go for very well separated compounds, even if i go back more and more to longer column (i feel the compound is cleaner, don't know why...)