I am working on the synthesis of polar ligand from pyridine and acetate groups. I tried different mixed solvent with different ratio for TLC (also trying hexane/ethyl acetate) but it was quite difficult because reactant didn't appear on TLC. Then I used dichloromethane /ethanol = 10 : 1 for TLC and it worked well. But when I tried the same solution for column chromatography, it couldn't elute the product. I think the product has poor solubility in dichloromethane. I need advice to choose the best solution for column chromatography. Why could I get different sepation result for TLC and column chromatography? Althoght I used the same mixed solvent.
Please look at the following below links which may help you in your analysis:
https://www.jove.com/science-education/10217/column-chromatography
https://www.chemistryviews.org/details/education/2101817/Tips_and_Tricks_for_the_Lab_Column_Choices.html
https://www.academia.edu/12328538/Choosing_a_Solvent_System_In_Tests_of_TLC_-_Technique
Thanks
Difference between TLC and column happens sometimes and I don't have an explanation of what could be the reason - possibly the ratio between solvent and substance amount or a difference in the silica properties. Purification of pyridines/imidazoles can be very tricky and unfortunately columns are always a trial and error game... I would probably try using chloroform/MeOH next (similar eluting power to what you used, but solubility might be different) or try an acetone-based system. It could also be interesting to use a low percentage of acid or base in your eluent system - maybe it's a protonation/deprotonation problem. I would try to find another system which works on TLC and then do a small scale column to test it.
Dear Dr. Husna Syaima, you may wish to describe your column chromatography protocols. But on a quick note, if you collected 5 fractions initially, you can extend same to say 10 fractions collected at a predetermined interval. It could likely be a factor of the molecular weight of the compound. If this does not suffice, you can try the suggestions of Dr. Christina Nadler
Regards,
Egbuna
Thank you Dr Christina Nadler and Mr. Chukwuebuka Egbuna . I'll keep trying
1.TLC AND COLUMN CHROMATOGRAPHY WORKS WITH DIFFERENT PRINCIPALS OF SEPARATION (Partisan and adsorption chromatography based on type of TLC plate and adsorbent used in column and give different Rf values for separation and same solvent mixtures systems may not be suitable for both... you have not specified the details of TLC plate/column used)
2.If your compound of interest is at a lower Rf value on TLC you may try to adsorb your compound mixture on adsorbent of column (preferably silcagel) and dry it and pack on top of column and elute the column with polar to non polar solvents to remove fast moving compounds and finally retain your compound of interest on top.This is one of the ways to separate..
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