I did preparative tlc of extract and i got a band of phenolic acid (confirmed by FeCl3 1% spray reagent). The compound uv vis spectra resembles chlorogenic acid spectral, but when i did tlc of the compound with the same mobile phase as preparative tlc before, i got two spot. One spot is the same spot on preparative tlc, the other is up to the solvent front. This unknown spot has blue and a little bit red colour and appear as streak. So i did preparative of the compound to isolate the spot without the unknown spot, but the uv vis spectral is different than the one with unknown spot. Could you please give me some explanation why this happen?thanks.
Hi Alik,
Uv-Vis spectra is a rough method for characterization, may chemical compounds gives absorption signal at the same wave length.
It seems that you have two compounds isolated, one is nonpolar (you named unknown spot) and the other is your phenolic acid.
After doing preparative tlc, first wash your sample with nonpolar solvent like petroleum ether to remove the unknown spot compound, the lifted will be your phenolic acid, dry it then use it. good luck
There is an isomer to chlorogenic acid called isochlorogenic acid which may be responsible for the 2nd spot
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