Chromatography Forum

Dear Chromatographers,

Is recycling & peak re-introduction doesn't goes well with semi-prep (upto 50ml/min) applications and hold good for prep chrmatography only??

Please post your views...Any theoritical justifications?

Rahul Yogi
rahul.yogi@gmail.com

Hi

For recycling, the system shold have some specs in order to do it well:

The pump should suck & pump constantly to avoid contamination of the recycled peak.

The control software should be able to handle it.

If you don´t need software control, you can buid it yourself with two three-way ball valves


Best regards
Chris

There is a chapter in my book "HPLC Columns" that deals with this technique and related approaches (pages 267 ff).

In brief: recycling through the pump is not a good approach due to bandspreading in the pump. A much better approach to recycling uses a "walking column". In principle, you constantly switch the relative position of two columns. First you go from column 1 to column 2. Once all your peaks are in column 2, column 2 becomes column 1 and column 1 becomes column 2. Now you are only dealing with the bandspreading in switching valves, which can be made very small. This is a reasonable technique to get a lot of plates for a small group of tighly eluting bands.

It's easy to do if you have a six ports/two positions valve, in some softwares, you can set the switching program. I did it once, but at last gave it up, I couldn't bear the low efficiency, so I prefered to spend some time to find a better method.