soma
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vanillin stain for tlc
The directions I've found recommend ethanol, (50 ml), sulfuric (.3 ml) and vanillin (1 gm). Has anyone tried isopropanol instead? It's easier and
cheaper to get.
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UC235
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I would probably use methanol instead but isopropanol should work as well. You just need a nonreactive carrier to deliver a mist of vanillin and acid
to the plate. Curlyarrow makes a somewhat more concentrated version using azeotropic ethanol (everclear) here: http://curlyarrow.blogspot.com/2006/11/lets-talk-about-tlcs-...
[Edited on 7-10-2016 by UC235]
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soma
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Thanks.
I was actually using one of the recipes from a poster on that curly arrow thread. I tried using phosphoric acid instead of sulfuric, at 1st, but
didn't get results. Guess it would take alot more. I think I saw some people using a 50% phosphoric in ethanol solution.
Rubbing alcohol is alot cheaper than everclear. I guess ip would evaporate slower.
[Edited on 7-10-2016 by soma]
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DJF90
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Heres the recipe I use:
Vanillin (24 g), acetic acid (10 mL), sulfuric acid (15 mL), ethanol (375 mL).
It is stored in a wide-neck amber glass jar at RT, and keeps well for 6 months or more.
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byko3y
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You need a friedel-crafts catalyst for vanilin to react with you substance. Dillute phosphoric acid is very poor catalyst, but concentrated one is
better, although I have no idea about how you are going to place vanillin-phosphoric acid mixture on the plate, considering solubility and viscousity
problems. 1 g vanillin in 100 ml 50% aqueous phosphoric acid is actully a know reagent.
Also I have no idea why acetic acid might be needed here.
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soma
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The vanillin is showing urea and imidazole but not n-acetylcysteine or nac-amide. Iodine shows the nac and nac amide. I'm wondering if it's possible
to get results using the iodine 1st and then the vanillin?
I'm dipping the silica aluminum back plate in the vanillin and then heating with a heat gun.
[Edited on 11-10-2016 by soma]
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DJF90
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Yes thats do-able. Stain with iodine first, mark the spots, heat gently with the heat gun to get rid of the iodine and then stain as usual with
vanillin.
EDIT: Pretty sure iodine also shows up imidazole.
[Edited on 11-10-2016 by DJF90]
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soma
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Yes, the iodine faintly shows the urea and imidazole.
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