Chromatography Forum

I am thinking using one very powerful technique for comprehensive analysis. right now, candidates has been narrowed down to uplc and CE. Could you help me out to choose one of them. are their plate count similar to each other? analysis time? any comprehensive paper on comparison between these two techniques? thanks a lot.

Well, right off the bat you can eliminate CE as being in any way comprehensive; because it only works for charged analytes.

when you say comprehensive, then for what? for what application?
CE is very popular and a strong solution for the bio world,
what type of detection do you intend to use as well will define how comprehensive you are capable of getting for your field of interest

both UHPLC and CE instruments are very sensitive ones, so it is good in one sense and bad in the other one,
check technical support and learn maintenance needs,
if you are told by the vendors not to worry then stop and look for end users to speak to.

No one instrument in a given configuration can give you the solution for everything in the universe.
the better the solution the more expensive it will be,
define your needs carefully

following on from adam's point, UPLC using conventional RP media is awful for exactly the things at which CE excels. Sugar phosphates, nucleotide phosphates etc. are a real struggle even with hilic, and hilic isn't the best choice if you have non-polar things present. Comprehensive is tricky by any technology (even assuming you can extract everything comprehensively).

Adam is also wrong: CE can be applied to uncharged analytes. If appropriate detergents are included, totally uncharged molecules can bind to detergent micelles and be dragged along because the detergent is charged. Uncharged things then separate on the basis of partitioning between solvent (which moves with the electroosmotic flow if any exists) and micelles that are being dragged elecrophoretically. It seems a strange thing to do, but the advantage is that there is still no pressure-driven bulk flow, so there is no laminar-flow distortion, and the peakwidth remains very narrow.

Jiang925, I believe that you work primarily with proteins, right? In very general (and oversimplified!) terms, the higher the molecular weight, the better the efficiency (plate number) of CE and the worse the efficiency of LC. That's one side of it. The other side is that CE has sensitivity issues (with UV detection) and injection reproducibility issues.

If you are looking for a technique to check your LC prep purification, CE has the advantage that it is pretty much orthogonal to LC in terms of selectivity.

thanks a lot. guys.
I am working on small molecules from food rather then on protein. It is very similar to metabolic profiling, which try to find out which compound is responsible for different flavor between two products.

Jiang925, I believe that you work primarily with proteins, right? In very general (and oversimplified!) terms, the higher the molecular weight, the better the efficiency (plate number) of CE and the worse the efficiency of LC. That's one side of it. The other side is that CE has sensitivity issues (with UV detection) and injection reproducibility issues.

If you are looking for a technique to check your LC prep purification, CE has the advantage that it is pretty much orthogonal to LC in terms of selectivity.

I am afraid that MECK technique cannot couple to MS, am I right?

following on from adam's point, UPLC using conventional RP media is awful for exactly the things at which CE excels. Sugar phosphates, nucleotide phosphates etc. are a real struggle even with hilic, and hilic isn't the best choice if you have non-polar things present. Comprehensive is tricky by any technology (even assuming you can extract everything comprehensively).

Adam is also wrong: CE can be applied to uncharged analytes. If appropriate detergents are included, totally uncharged molecules can bind to detergent micelles and be dragged along because the detergent is charged. Uncharged things then separate on the basis of partitioning between solvent (which moves with the electroosmotic flow if any exists) and micelles that are being dragged elecrophoretically. It seems a strange thing to do, but the advantage is that there is still no pressure-driven bulk flow, so there is no laminar-flow distortion, and the peakwidth remains very narrow.

but for small metabolites, are their efficiency quite similar. and I think CE also does not have enough peak capacity even they use MECK technique.

Jiang925, I believe that you work primarily with proteins, right? In very general (and oversimplified!) terms, the higher the molecular weight, the better the efficiency (plate number) of CE and the worse the efficiency of LC. That's one side of it. The other side is that CE has sensitivity issues (with UV detection) and injection reproducibility issues.

If you are looking for a technique to check your LC prep purification, CE has the advantage that it is pretty much orthogonal to LC in terms of selectivity.

I certainly wouldn't put detergents into an MS... ion pair reagents give me the heebie jeebies already!

thanks a lot. guys.
I am working on small molecules from food rather then on protein. It is very similar to metabolic profiling, which try to find out which compound is responsible for different flavor between two products.

If the flavours are odours use GC, with a sniff port, and then heart cut the part of the chromatogram where the target odour elutes.

If the flavours are tastes you are stuck with liquid phase separations.

Peter