Frequently Asked Questions

What is an appropriate flow rate for a certain column?

For each particle size, there is an optimal linear flow rate with respect to column efficiency, according to the van Deemter plot.

Optimal flow rate (ml/min) for Kromasil columns depending on particle size and column diameter.
  3.5 µm 5 µm 10 µm 13 µm 16 µm
Linear flow rate
(cm/min)
7.1 4.7 3.3 2.4 1.9
2.1 mm ID 0.3 0.2 - - -
4.6 mm ID 1.5 1.0 0.7 0.5 0.4
10 mm ID - 4.7 3.7 2.4 1.9
21.2 mm ID - 21 15 10 8.5

For shorter separation times, the flow rate can however be increased until the pressure drop limit of the HPLC pump is reached, e.g. ca 400 bar.

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