Chromatography Forum

Hey All

I was wondering: does anyone know of any companies that sell HPLC equipment for open-tubular column work. I would appreciate any leads that you could provide.

Thanks in Advance
Adam

Michrom, Exsigent, and Dionex come to mind (I'm probably missing some).

There's a fairly long list of manufacturers' web sites here:
http://www.lcresources.com/wiki/index.p ... Q:MoreInfo

I'd be interested in a clarification of this discussion. An open tubular column is one in which the stationary phase is coated on the inner walls of the column, as used in gas chromatography. Due to the much lower values of the solute diffusion coefficient in liquids compared with gases, such columns have, I thought , only seen investigations in research labs since the requirement is for a column i.d. < 10 um. I did not think such columns were available commercially.

Do you mean capillary columns? These are actually packed with particles. Typically the tube diameter is 30-200um and the particles within are 3 or 5um. In GC, the terms open tubular and capillary are used interchangeably, because only open tubular type capillary columns are used in GC. In LC it is different. Maybe I am wrong and someone out there is routinely using open tubular HPLC columns.

Victor

I agree 100% with everything you said: including the diffusivity problem and the terminology.

But, yes, I am referring to open-tubular HPLC - with stationary phase coated on the wall (what GC people call a capillary column: as you pointed out). I'm not referring to packed columns.

It isn't common, but there has definitely been some work done with open-tubular HPLC.

Adam

Adam-thanks for your answer. I'd be interested why you are looking for such a system. Are you trying to achieve very high plate counts with a very long column and are prepared to put up with long analysis times and low sample capacity?

Victor

It is a long story, so I will give only a very brief answer.

Open-tubular columns can offer higher plate counts than any packed alternative: and we feel there may be a need for this.

Certainly the problems of capacity and (especially) the long analysis times present important concerns. But there may be ways to deal with these problems.

Never say never, in science. Adam

Adam,

If you are looking for high plate counts, I would suggest coupling together 25cm 5um packed columns of normal dimensions. If you do not need aggresive mobile phases, you can work at somewhat elevated temperature to reduce the back pressure. You should be able to achieve 100,000 plates in such a system if you are careful with 4 or 5 coupled columns of 1 -1.25 m total length. Just a thought-might be easier if this sort of system will give you what you want.