Chromatography Forum

Hi, we are thinking of purchasing a UPLc system. We mostly perform size exclusion chromatography. I was wondering if there are any size exclusion UPLC columns in the market that we can use with the new system. Thanks

The simple answer to this question is no. If you purchase a UPLC and only do SEC with it, you are wasting you money. UPLC is primarly small particle reverse phase chromatography (there are some small particle silicas that you can to do NP on) and it works quite well for that. You get none of the benifits (speed, increased resolution) running SEC on a system like that.

thanks AA

Can you elaborate on this.

Why wouldn't you get a lot of benefits with small particles in SEC.

You don't have partitioning back and forth between mobile phase and stationary phase, but you still have band broadening by the mobile phase mass transfer mechanism, i.e. the C term of the van Deemter. And this is generally believed to be the most significant band broadening issue at high linear velocities.

I am curious to understand this better.

Thanks

I did not say that you would not see benefit if there were small particle SEC columns. I said (or tried to say) that when running SEC columns, as they exist today, you would see none of the benifits.

Of course, particle size and particle size distribution can have a significant impact on volumetric flow and resolution in the packed column bed. However, as you lower the particle size, the backpressue increases (with constant flow rate). Traditional SEC packing are quite fragile, and prone to compression and I think that this would present some problems. I have seen some papers that employ modified silicas for SEC using smaller particles (down to 3 um) so maybe SECUPLC is something to look forward to in the future.

...so maybe SECUPLC is something to look forward to in the future.

SEUHPLC is more accurate, no?

Tosoh´s TSK-Gel Super SW columns nicely show how you can gain resolution. But there is a limit of course, if the particle sice is lower than the pore you do not have much of a stat. phase.

UPLC in design to perform at high pressure (until 15 000 psi) and SEC doesn't generate so much pressure. So you don't need UPLC system.

The only benefit might be a low volume system, but I'm not convicted.