So, i want to isolate coumarin from a plant extract. I already did fractination using column chromatography using ethyl acetate:ethanol:water (100:26:10) as mobile phase. The problem was in some fractions that has coumarin spot in it, there was this unknown spot with the same Rf in every fraction. This unknown spot was in blue color as coumarin spot, but if i spray them with KOH 10%, the color of the unknown spot did not intensified.
I already did a preparative tlc to get this coumarin isolate, and did a purity test, but this unknown spot appeared again.
So, what is this unknown spot? Is it an artifact?
Thankyou.
You should do NMR to confirm purity. Sometimes things degrade on TLC and can give multiple spots. If it has the same Rf as coumarin though, how do you know its not coumarin?
@Greg Petruncio thankyou for the suggestion. I sprayed the TLC plate using KOH 5%, for coumarin, the color intensified.. But this unknown spot did not change.
Gotcha. Sometimes I have isolated pure compounds and the NMR looks great but they will show a small extra spot on TLC; not always but sometimes.
My suggestion is to do NMR if you can to confirm pure compound. Additionally you can do melting point test if you dont have NMR access.
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