By Anonymous on Tuesday, April 27, 2004 - 06:52 am:
can anyone recomend an C18 HPLC column that is stable in a wide range of pH (2-12) and supports 100% water for several runs?
does TFA (0,1%) always make shorter the lifetime of the columns or there are more resistant types?
By Uwe Neue on Tuesday, April 27, 2004 - 04:48 pm:
XTerra MS C18 is stable over a wide pH range. If you give me the details I can advise how stable it is for your application at pH 11 to 12. We have run the column for 45 days at 30 degrees at pH 11.5.
A trifunctionally bonded column (such as the column mentioned above) is more resistant to TFA than monofunctionally bonded columns,
By Anonymous on Wednesday, April 28, 2004 - 01:48 am:
thanks Uwe Neue,
I want to use this column to separate acidic compounds trying both with ion suppression (TFA 0.1%) and ion pair (TEA 0.1%) solvents. is in your experience, this xterra MS C18 resistant at 100% water? someone told me after using this column at 100% water it is dewetted (?) and it needs to be rigenerate with 100% organic solvent.
what is the difference between xterra RP18 and Xterra MS C18?
By Uwe Neue on Wednesday, April 28, 2004 - 04:18 pm:
Dewetting is not a problem with either of the XTerra packings. XTerra MS C18 is a C18 based on a trifunctional silane and has good stability in the acidic pH range. XTerra RP 18 has an embedded polar group, but is based on a monofunctional silane. It gives different selectivity than the classical C18, but due to the monofunctional bonding, it is not stable below pH 2.
By Anonymous on Saturday, May 1, 2004 - 12:49 pm:
that's different from wat waters -rep told me. he told me it is not a good idea to use xterra with 100% water.
why do you think different about this?
By DW on Saturday, May 1, 2004 - 07:11 pm:
The Waters rep was wrong. All XTerra columns are compatible with 100% aqueous conditions. Call 800-252-4752 to confirm and ask to speak with someone from Chemistry Technical Service.
Don't be too hard on the poor sales person for being wrong, Waters has a lot of products.
In addition, if Uwe says the columns are 100% aqueous compatible, you can be pretty sure he's right.
By annav on Sunday, May 2, 2004 - 01:18 pm:
hello,
I would like to know if an HPLC method (gradient) already set up on a
supelcosil LC18 column can be used with a xterra MS C18
column without further changes or should I expect sensible changes in the
separation of the compounds and ritention time?
thanks for the precious suggestions...
annav
By tom jupille on Sunday, May 2, 2004 - 04:37 pm:
You have to assume that some changes in conditions will be required with *any* column change. Rheodyne makes a database of columns that will let you find the closest equivalent column to your existing one.
http://www.rheodyne.com/products/chromatography/columnmatch/index.asp
They also make a program to identify the combination of changes in conditions that will most closely match your new column to your old:
http://www.rheodyne.com/products/chromatography/methodmatch/
I believe you can download "30-day trial" versions of both.
By way of "truth in advertising", I was involved in the development of both programs prior to the recent "spin-out" of LC Resources by Rheodyne. I do think they represent the best way to accomplish what you're trying to do.