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cryofocusing used on hplc?
Posted: Wed Oct 19, 2005 7:37 am
by smiley
anyone experienced using cryofocusing on hplc? what is the major stuff to make it work?
my main concern is the sampling capacity since the amount of compound is larger than in GC, what scale of the cooling flow and how fast the heating desorption should it be.
any comments is greatly appreciated.
Posted: Wed Oct 19, 2005 10:59 pm
by JA
People actually do this?
Posted: Thu Oct 20, 2005 6:16 am
by tom jupille
As far as I know, cryofocusing is used in GC, not LC.
The LC equivalent would be on-column concentration, in which the sample is dissolved in a solvent which is much weaker than the mobile phase, allowing a large volume of dilute sample to be injected without significant band broadening (the analytes "stack up" on the head of the column. This is done routinely.
Posted: Thu Oct 20, 2005 9:35 am
by Alex Buske
I saw a poster on the 2002 International symposium on Chromatography:
"Development of a column oven with an incorporated cold spot for large volume injections in capillary liqiud chromatography" by A. Holm, P. Molander, E. Lundanes and T. Greibrokk of the department of Chemistry, University of Oslo
Don't know if there is any further information availible, but my medium term storage seems to be somewhat better then thought
Alex
Posted: Thu Oct 20, 2005 2:07 pm
by DR
Temperature does have some effect on the partition coefficient, but mobile phase strength has a much more significant impact on it. I guess if your sample is either unstable or not soluble in a weaker mobile phase, you would have to look at alternative methods for loading a column (Tom's example is quite common in LC purification exercises). Aside from that, manipulating partition coefficients in LC via temperature strikes me in the same way as counting the Queen Mary's deck chairs by weighing the boat.
I guess I'll have to at least read that abstract...
Posted: Thu Oct 20, 2005 4:44 pm
by tom jupille
Alex, you just jogged my memory.
There is one company (Selerity) that has been promoting temperature-programmed LC, using zirconia-based packings. That's the only situation where cryofocusing would be relevant in LC. They don't have anything specific about it on their web site, however.
http://www.selerity.com/
Posted: Thu Oct 20, 2005 6:10 pm
by Kostas Petritis
In the proteomics field there was some use for it as well. The idea is, if you are using a trapping column to load your sample and your separation column is temperature control at something like 40-50 C, then you would have some benefit to cool down your trapping column (or just room temperature) in order to be sure that you are trapping as much as possible.
That's in theory, I didn't see any significant gains by doing so... Also what you will trap are in general pretty small peptides which are not of much interest anyways in proteomics...