You can get an idea about which type of compound you have. For example, iodine vapors can detect polycyclic aromatic hydrocarbons, phenolic steroids, fatty acids, esters and alkaloids as well. Maybe this book could help you http://altair.od.ua/analit/Tonkosloynaya%20hromatografiya.%20Reagenti%20i%20metodi%20opredeleniya262.pdf
Dear Sudheer, Iodine vapour is one of the reagents used to identify the position of compounds on a developed TLC plate. Normally most plant compounds adsorb iodine and appear as brown spots when the plate is suspended in a jar containing iodine.
Many people use iodine vapors when they are discouraged from all other indicators. It is also called a universal indicator when used for derivatizing TLC of herbal compounds. And in most of the cases, I have seen that it is successful.
The iodine act as indicator, and generally the reaction is reversible, if you heat a little the tlc the iodine will go away then you can use another indicator
THIN-LAYER CHROMATOGRAPHY. A Laboratory Handbook. Second Edition, Revised and Expanded. Edited by Egon Stahl; you can find all detail
Iodine complexes with starch and other carbohydrates producing blue color. however in TLC plate it makes brownish color coz of solvent effect. offcourse it binds with glycosides also. This coordinate bond formation. Now there are possibilities redox reactions too. But that may not make color reactions. Under UV its visible.
It just gives you a spot which indicates the presence of a compound.
iodine "sticks" to organic compounds. You will see your chromatogram!
Iodine vapours react with Starch forming complex revealed as blue colour spot in TLC.With TRIGLYCERIDES ,Iodine vapours produces brown colour spots.
Iodine complexes with double C=C bonds which are very often found on an organic compound skeleton. So, it makes iodine a general and reversible revealer of organic substances on TLC.
Addressing some of the points above:
-if you dry the plate properly before exposing to iodine you will not see solvent staining.
-as it is reversible you can stain - mark spots on he TLC plate, allow the iodine to evaporate and then scrape the spots for compound isolation.
-staining for too long with iodine can lead to irreversible staining of some lipids.
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