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Posted: Fri Oct 16, 2009 3:37 pm
by Uwe Neue
Grzesiek
The issue has been described in detail in the publication by my colleagues below, which also demonstrates that the problem does not exist for EPG packings. We do have data on newer packings as well.
Mechanism of retention loss when C8 and C18 HPLC columns are used with highly aqueous mobile phases
Journal of Chromatography A, Volume 1075, Issues 1-2, 20 May 2005, Pages 177-183
Thomas H. Walter, Pamela Iraneta, Mark Capparella
Posted: Fri Oct 16, 2009 8:23 pm
by grzesiek
Great, thanks
Posted: Sat Oct 17, 2009 9:01 am
by HW Mueller
Agreed that mixed mode is valuable, I just kick when the impression arises that other columns are obsolete. As a matter of fact I would really like to play with a silica C18 which is not mixed mode (that is, developments away from mixed mode should perhaps be more pursued?).
Posted: Mon Oct 19, 2009 7:17 pm
by LC_labrat
As you can see, we have some sensitive people on this forum
I have to disagree. What we have are people with problems trying to find solutions. These solutions should be supported by good science. I appreciate having knowledgeable column representatives on the board. But I don't appreciate sales tactics, it sends good people away faster than announcing the FDA is in the lab.
Posted: Mon Oct 19, 2009 11:49 pm
by chris.singleton
Hi Kerri,
I have run the XBridge columns at high and low pH and I never saw a problem. If I recall correctly (I used to work there a few years ago)there was an application note from Waters where they swtiched from high to low pH, back and forth for several hundred injections each. In general they have been robust. Without saying that other manufacturers are bad, I will say that I like Waters and ACE columns for most of my applications, I have had good results from them. I've had other colleagues absolutely swear by ACE columns.
If you are doing high water content, I will tell you my strategy. Here at BiogenIdec doing small molecules, the majority of my columns are C18. Then if I have more polar compounds I have a couple of embedded polar group C18 columns which I run high aqueous in, and I have a HILIC column for very polar compounds but I rarely use it. The majority of small molecules pharmaceuticals that I have worked with are weak bases, and if they are polar I tried the strategy above; occasionally I did switch pH but it was not as often.
Chris Singleton
DMPK, BiogenIdec