[suzielayusuf]

hello,,i need help regarding on building new solvent system for thin layer chromatography of my extract..i'm doing anticancer study, using quercus infectoria (QI) extract.i'm using quercus infectoria ethyl acetate extract, where this extract was obtained through the gradient extraction. for the extraction procedure, firstly i soaked the quercus powder in n-hexane for 5 days, then i filtered and I use the residue and soaked in ethyl acetate for another 5 days, then i filtered again and by using the same residue i soaked it in the methanol..after the extraction i used the methanol, ehyl acetate and methanol extract for anticancer study. from the screening i found that the ethyl acetate extract was the most potent.now, i have to do the bioassay guided fractionation to get the pure compound. i did the tlc for my extract, but i just cant get the right solvent system, because my tlc was tailed and no band appear..can u help me?

[Arkcon]

You gave us all of the information that we didn't need, and none of the information that we did need.  You might have better results if you had some idea of the structure of your desired compound, but that may be difficult for you with this sample.  But try to keep it in mind, as you experiment or search literature further.

Take into account the solvent you used in the TLC (which you didn't mention,) if it tails your active, change the chemistry of your next solvent.  If it was originally more polar, try something less polar, as examples.

[teejay0023]

yes you need to try many solvent systems before you give up.  hexane/ethyl acetate and DCM/methanol are quite common.  ethyl acetate/methanol, hexane/ether, etc...  find a book chapter on TLC.  also if your compounds have amino groups this can cause streaking.  try adding 1-2% triethylamine to the eluent, this can sometimes sharpen up bands/spots.  or if your compound has an amide or carboxylic acid, try adding 1-2% acetic acid.  this can also sharpen things up.  good luck.