By Anonymous on Tuesday, February 24, 2004 - 06:21 am:
I've got 2 questions. Firstly I've been analysing aromatic amines using a strong cation exchange on silica (Luna SCX) and get good retention (mp 20mM KH2PO4 85% ACN 15%). I get a nice separation but I have no feel for how robust these SCX methods are. Has anyone stressed one of these columns with a thousand injections? and has it been robust?
The other thing I could try is derivatisation. A lot of procedures use ortho-phthalaldehyde (try saying that after a few beers!). Given that the amines are in Methanol is that the easiest way to go?
Regards
John
By Consumer Products Guy on Tuesday, February 24, 2004 - 06:39 am:
I wouldn't bother with derivatization as your compounds are already aromatics (UV detection) and you state that you're getting good separation; why add extra step(s)? I'd derivatize for non-aromatic amines.
By Anonymous on Wednesday, February 25, 2004 - 12:26 am:
One of the aromatic amines has an acid (SO3H)group as well and appears to be too polar to be retained in any system I've tried. I may have to derivatize because of that one.
regards
John
By Uwe Neue on Wednesday, February 25, 2004 - 03:27 pm:
You can potentially use silica itself as the ion-exchanger. It is a weak ion-exchanger, of course, but since there is nothing on the surface, nothing can wash off. It is commonly used for HILIC applications with less than 50% water.
By Andreas Neumaier on Wednesday, March 3, 2004 - 01:38 am:
Another way to seperate aromate amines is to use a c8/18 with high conc of water (85 to 95%) at low pH (0,5 to 1% of 0,5M sulfuric acid).
When seperation of the acidic one from the others fails with this conditions use a YMC Pro c4/8/18 because they show some very interesting increase of retention for aromates with -SO3H groups under such conditions.
Maybe you have to run a (fast) gradient to seperate all the compounds in pleasent time.