Sciencemadness Discussion Board

Al2O3 tlc plates

soma - 3-8-2016 at 02:13

I've been looking for aluminum oxide tlc plates but have only found sources that sell large quantities for large prices. Anyone know where I could get a small quantity for a small price? I got some silica plates but want to try out the alumina also as I've read that alumina is good for separating amines.



SupaVillain - 8-8-2016 at 18:08

Search for "alumina strip" on ebay, I looked it up but I'm not sure if this is what you're talking about.
http://www.ebay.com/sch/i.html?_from=R40&_trksid=p205060...

byko3y - 9-8-2016 at 09:13

I'm sure those ceramic strips are not the same as ativated alumina for TLC. Ceramic is almost solid, while TLC alumina is highly porous.
If you search for lower price, you might wanna try to make your own tlc plates, by activating and sieving a regular Al2O3, then mix with gypsum and place a thin layer onto glass, foil or plastic sheet. Jut in case you don't want to spend 120$ on commercial plates.
There are very few people who would sell you 1-3 plates, because nobody would bother repackaging this small amount for low price, considering low
liquidity and the fact usual consumers are laboratories that need a lot of this stuff.
But you did not mention your country, very few people would even bother answering.

SupaVillain - 10-8-2016 at 20:38

Well my alumina strips are actually see through, like if I slide one behind the other, I can see where its edge is at. Might not be due to porosity, but perhaps OP can find out by asking the seller. I'm not informed of what "activated" alumina is so...

brubei - 11-8-2016 at 01:57

Quote: Originally posted by soma  
I've been looking for aluminum oxide tlc plates but have only found sources that sell large quantities for large prices. Anyone know where I could get a small quantity for a small price? I got some silica plates but want to try out the alumina also as I've read that alumina is good for separating amines.

Al2O3 give sometime best results than silice due to its higher pH, reducing amine to solid phase affinity.

here are somes http://www.ebay.com/itm/25pc-pk-Analtech-TLC-Uniplates-Alumi...


You can also dip your plates in 0.1 mol/L potassium hydroxide in methanol, and dry them to increase the pH of the solid phase.
Another path is to add triethylamine or ammonia is the liquid phase.

I have tried these 2 last purposes for resolution of pharmaceuticals and drugs on silica tlc with great succes !

Here are the recommended solvent:

System TA
n Plates: Silica gel G, 250 m m thick, dipped in, or sprayed with, 0.1 mol/L
potassium hydroxide in methanol, and dried.
n Mobile phase: Methanol–strong ammonia solution (100 : 1.5).

System TB
n Plates: Silica gel G, 250 m m thick, dipped in, or sprayed with, 0.1 mol/L
potassium hydroxide in methanol, and dried.
n Mobile phase: Cyclohexane–toluene–diethylamine (75 : 15 : 10).

System TC
n Plates: Silica gel G, 250 m m thick, dipped in, or sprayed with, 0.1 mol/L
potassium hydroxide in methanol, and dried.
n Mobile phase: Chloroform–methanol (90 : 10).

System TL
n Plates: Silica gel G, 250 m m thick, dipped in, or sprayed with, 0.1 mol/L
potassium hydroxide in methanol, and dried.
n Mobile phase: Acetone.

Stead AH et al. (). Analyst 107: 1106–1168.
(Clarke’s Analysis of Drugs and Poisons, 4th ed)




[Edited on 11-8-2016 by brubei]

byko3y - 11-8-2016 at 14:31

And once again the substrates, for which solvent mixtures should be used, are lost, and instead we've got the same try-and-guess method.
Methanol-ammonia is used for hydrophilic amines (basic methanol solvent), cyclohexane-toluene-diethylamine - for hydrophobic (basic cyclohexane solvent), acetone - for differentiation between primary, secondary, tertiary amines. I'm not sure why something like triethylamine is not used together with acetone.

soma - 16-8-2016 at 01:29

Thanks.

Looks like good information. At this point I'm thinking of trying to make my own plates. I want to put a uv indicator in. Anyone have information on how much indicator to plaster to alumina/silica to add? (and what indicator to use?)

I'm thinking of adding vinegar to the mix so that I'll have more time before it hardens. So the methanol-KOH dip is interesting.