Electra
Hazard to Others
Posts: 179
Registered: 11-12-2013
Member Is Offline
Mood: No Mood
|
|
TLC with ionic compounds? Doable?
I saw one source online say it doesn't work very well, but I can't quite figure why. If water was used as a solvent, wouldn't bulkier ions travel up
the plate at different speeds depending on their size?
|
|
|
deltaH
Dangerous source of unreferenced speculation
Posts: 1663
Registered: 30-9-2013
Location: South Africa
Member Is Offline
Mood: Heavily protonated
|
|
I would imagine that you would need an ionic stationary phase for high resolution, like a powdered ion exchange resin (if your compounds are small or
large) or an inorganic material like a zeolite (if your compounds are very small and positively charged... like metallic cations)?
In the case of using an ion exchange resin, you would have to pick a cationic or anionic material for the stationary phase depending on the charge of
the compounds you want to resolve or use a mixed charge material to resolve either, all three are commercially available.
I would imagine that once the compounds are loaded onto the stationary phase, that you would need to elute with a salt solution. Instead of adjusting
the polarity of the eluent as you would with silica, in this case you would adjust the ionic strength of the eluent.
In terms of the usual stationary phase, like silica etc. I don't think the ions would adsorb very well, hence the equilibrium between the stationary
phase and solvent would hardly be existing (will be strongly favoured towards being in water) and so you wouldn't have many theoretical plates and so
poor separation.
This is somewhat speculative, I'm no expert, just how I would do it if I had to and couldn't find anything on it. I'm sure there's tons of literature
on it though 
[Edited on 18-10-2015 by deltaH]
|
|
|
AvBaeyer
National Hazard
Posts: 651
Registered: 25-2-2014
Location: CA
Member Is Offline
Mood: No Mood
|
|
What kind of ionic compounds are you considering - organic or inorganic? I have Stahl's book on TLC - it's encyclopedic. So if you can be more
specific, perhaps I can give you some leads.
AvB
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
