No idea what kind of interaction you want to do but in general we use a flow-rate of minimal 30 ul/min in the Biacore 3000 and sometimes higher. Mass transport can be lower at higher flow rates but for pure 1:1 kinetics flow rate should not be of influence.

Thank you so much! I am working with small molecule - protein interactions and previously people have used a very low flow rate (7-10 uL/min) for this interaction. But I also think higher flow rate is preferred to limit mass transport.

I agree with Arnoud Marquart.