Chromatography Forum

Hi all,

I have not used packed columns for long, and now I start to use some for gas analysis. For capillaries, it's quite easy to set the optimum velocity (flowrate) of carries gas. But for packed columns, I really do not know how to calculate the optimum flowrate according to its diameter and/or particle size. Anyone can help ?
Thanks

The optimum flow rate can make a difference in the number of plates generated using packed columns. But the other column factors which have decreased the number of plates are so large that the small gain in optimizing the flow rate are usually essentially non-detectable.

Use temperature and the selectivity of the phase to optimize the separation you need. 1mm ID columns usually have flows between 5 and 15 mL/min, 2.1mm ID columns have flows between 15 and 60 mL/min, and 4mm ID columns have flows between 20 and 100 mL/min flows.

GENERALLY, use the lower end of the flow rates I have listed and your results will be close to optimal. Your mileage may vary. For example, to reach a 1 minute cycle time to measure hydrogen in a process analyzer using a backflush valve and 1mm ID columns, a flow of 100mL/min was once required.

best wishes,

Rod

Very clear to me now!
Thank you Rod.