Can someone suggest the mobile phase for TLC of alkaloids isolated as Fraction A and Fraction B as described in figure? ( Isolation of alkaloids carried out as described by Maldoni, 1991).
Fraction A, probably dichloromethane/methanol, perhaps with a little triethyl amine added. If adding base, keep the methanol below 30%. If the alkaloids aren't polar
For fraction B, that is very polar. You may need a C18 plate for that, or if the binders on your TLC plates can stand it, try aqueous normal phase.
Also consider something like an amine TLC plate.
http://www.isco.com/WebProductFiles/Applications/101/Application_Notes/AN84_RediSep_Rf_Gold_Silica_and_Highly_Polar_Solvents.pdf
http://www.isco.com/WebProductFiles/Applications/101/Poster_and_Paper_Reprints/Method_Development_Strategies_for_Amine_Columns.pdf
For fraction B you can also try an appropriate Amberlist interchange resin.
Try Chloroform:Methanol combinations for fraction A. For fraction B, you can use n-butanol:acetic acid:water (4:1:3). Otherwise alkaloids are also visible in Chloroform: Glacial Acetic acid: Methanol: Water (16:8:3:2). I am sure you will get some new directions using these combinations.
For alkaloid separation Toluene: Ethylacetate: Diethylamine (7:2:1) is a good sovent. You can try. You can see the book Plant Drug Analysis- A thin layer chromatography atlas by H. Wagner.
extract your plant material with 2% H2SO4 and use any of these solvent systems for TLC to elute alkaloids.
ether : acetone : diethylamine (80 : 20 : 5)
ether : methanol : diethylamine (90 : 5 : 5); n-hexane
chloroform : diethylamine (50 : 40 : 10)
benzene – chloroform : acetone : diethylamine (80 : 25 : 30 : 5)
You can try extraction process with chilled methanol and try the solvent system toluene:ethyl acetate:formic acid-4:5:1 for better separation of alkaloids.
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