How does changing flow affect gradient separation?

[Mike H.]

Easy question. If running a gradient with a flow of 1.5 ml/min, should I decrease the slope of the gradient 33% if I decide to run at 1 ml/min? Thx

[HPLCaddict]

Yes.
Basically, in order to keep the separation the same, you have to look at the gradient volume.
Gradient volume = Flow-rate x gradient-time.

If you decrease the flow-rate by 33%, you should increase the gradient time by 33% to keep the gradient volume the same. This should give you basically the same separation (at a longer run-time).

[Mike H.]

Thank you.