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Flash Column Chromatography Problem - nothing eluting
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Lukash Tatarka
Flash Column Chromatography Problem - nothing eluting
Pure hexane is a poor solvent and as lipophilic as you can get so. Try to dissolve your material before loading. Toluene is a better solvent but usually dont impact on Rf
Pure hexane is a poor solvent and as lipophilic as you can get so. Try to dissolve your material before loading. Toluene is a better solvent but usually dont impact on Rf
Probably TLC was too concentrated, and it smeared up the plate under non equilibrating conditions. Like Babcock_Hall said: always flush with polar solvent like 100% EtOAc or 100% acetone or 10% MeOH/DCM to elute it or decomp off the column. Could be a solid and it precipitated at the baseline therfore not moving far. These are common problems. Try TLC again with dilute sample.
Probably TLC was too concentrated, and it smeared up the plate under non equilibrating conditions. Like Babcock_Hall said: always flush with polar solvent like 100% EtOAc or 100% acetone or 10% MeOH/DCM to elute it or decomp off the column. Could be a solid and it precipitated at the baseline therfore not moving far. These are common problems. Try TLC again with dilute sample.
I am not sure what is going on. One thing you could try is a step gradient with increasing percentages of diethyl ether, DCM, or some other solvent in the hexane, as opposed to moving immediately to the flushing step.
I am not sure what is going on. One thing you could try is a step gradient with increasing percentages of diethyl ether, DCM, or some other solvent in the hexane, as opposed to moving immediately to the flushing step.
Probably TLC was too concentrated, and it smeared up the plate under non equilibrating conditions. Like Babcock_Hall said: always flush with polar solvent like 100% EtOAc or 100% acetone or 10% MeOH/DCM to elute it or decomp off the column. Could be a solid and it precipitated at the baseline therfore not moving far. These are common problems. Try TLC again with dilute sample.
The TLC didn't have a smeared appearance so this didn't cross my mind, but it's definitely ssomething to consider. It is a solid yeah, so your idea that it precipitated at the top of the column seemes likely. I flushed with ethyl acetate to recover everything thankfully. I'll try with a different solvent system. It's strange that the literature procedure states the same solvent system. I wonder what I was doing differently, or if they misreported.
Thank you very much for the advice. If anyone else has any thoughts please let me know. I am still very concerned and want to make sure I can avoid this in future.
Probably TLC was too concentrated, and it smeared up the plate under non equilibrating conditions. Like Babcock_Hall said: always flush with polar solvent like 100% EtOAc or 100% acetone or 10% MeOH/DCM to elute it or decomp off the column. Could be a solid and it precipitated at the baseline therfore not moving far. These are common problems. Try TLC again with dilute sample.
The TLC didn't have a smeared appearance so this didn't cross my mind, but it's definitely ssomething to consider. It is a solid yeah, so your idea that it precipitated at the top of the column seemes likely. I flushed with ethyl acetate to recover everything thankfully. I'll try with a different solvent system. It's strange that the literature procedure states the same solvent system. I wonder what I was doing differently, or if they misreported.
Thank you very much for the advice. If anyone else has any thoughts please let me know. I am still very concerned and want to make sure I can avoid this in future.
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The TLC didn't have a smeared appearance so this didn't cross my mind, but it's definitely ssomething to consider. It is a solid yeah, so your idea that it precipitated at the top of the column seemes likely. I flushed with ethyl acetate to recover everything thankfully. I'll try with a different solvent system.
It's strange that the literature procedure states the same solvent system. I wonder what I was doing differently, or if they misreported.
Thank you very much for the advice. If anyone else has any thoughts please let me know. I am still very concerned and want to make sure I can avoid this in future.
Edit: typo
The TLC didn't have a smeared appearance so this didn't cross my mind, but it's definitely ssomething to consider. It is a solid yeah, so your idea that it precipitated at the top of the column seemes likely. I flushed with ethyl acetate to recover everything thankfully. I'll try with a different solvent system.
It's strange that the literature procedure states the same solvent system. I wonder what I was doing differently, or if they misreported.
Thank you very much for the advice. If anyone else has any thoughts please let me know. I am still very concerned and want to make sure I can avoid this in future.
Edit: typo
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