Chromatography Forum

Hi all!
The little wierd question appeared. Did someone try to set an analytical tasks using semi-preparative LC (for instance with flow rate 0.5-150 ml/min) as HPLC (on the low flow rate, about 0.5-1 ml/min)?
What do you think about this idea, even with changing tubings for proper ID?

Hello

You can scale from: analytical to semi-prep to prep and other way around.
Don't forget that it is not only column dimensions and tubing. It is pump and sampler volume as well.

Regards

Tomasz Kubowicz

Tomasz, thank you for reply.
I not so clearly put the question. Main question is could the semi-preparative pump on the low flow-rate (the bottom line of range) give acceptable characteristics of flow, mixture and pressure stability? Will the analytical runnings have reproducible retention times?

That depends on the pump and on your definition of "acceptable". Check the manufacturer's specifications for the pump. As long as you are within their specified flow range, then the pump *should* meet the specified accuracy and precision.

It makes sense.
Saying "acceptable" I meant at least retaining of pump characteristics at lowest flow rate. Unfortunatelly, not always the characteristics are given for entire range of flow rate and pressure.
I hoped that someone already faced with similar task. Maybe there are typical problems that I need to know about (exepting high dead volume in line of course).

As noted earlier, it depends on the EXACT pump model and configuration (not enough info provided). The internal volume of the pump head, the tubing, flow cell, injector, the column size/volume and all related parts must be taken into account to find out.

In general, many of those single pump head units which claim they can be used at a wide range of flow rates, example 0.100 to 100 ml, are just exaggerations. Even if they can operate at pressure and deliver the needed flow rates, most will not do so at a level which is usable for chromatography applications. By design, most pumps have a very limited usable range and anything outside that are generally not used (opinion: BEST to always buy dedicated pumps designed for a specific range. Those all-in-one analytical to semi-prep pumps are often a waste of money).