Are you looking for the complex calculation (using the van Deemter plot curve, which can be obtained for free online or from one of the wonderful books on chromatography) or just the main guidelines we use in practice to develop methods? A formal plot and calculation can be made which takes into account the particle size and efficiency to determine the optimum flow range. But there is a better way for everyday purposes.

For practical considerations, to maintain linear velocity we use 1.00 ml/min for 4.6 mm ID columns, 200 ul/min for 2.1 mm ID columns and 50 ul/min for 1 mm ID columns. LINK: https://hplctips.blogspot.com/2013/04/using-smaller-diameter-hplc-columns.html

To OPTIMIZE the flow rate for a specific method and column (as column diameter and particle size need to be accounted for), make several runs at different flow rates (e.g. Try 5 different flow rates near, at and above the linear velocity), then PLOT flow rate vs PLATE #. This will help you determine an optimum value.

Hi, in addition please read the link below

http://www.chromacademy.com/lms/sco3/Theory_Of_HPLC_Band_Broadening.pdf

Dear Bill,

Dear Gunawan,

Thanks a lot, I highly appreciate your generous and you useful answers. Definitely, they both make sense.

Best regards

Saddam