8. Downscaling on a Conventional HPLC System

4.6 mm I.D. columns are widely used with conventional HPLC systems. By decreasing the I.D. to 3.0 mm, the solvent consumption can be reduced by 60% and comparable results can be obtained. There are no complicated changes in the conditions, and you only have to reduce the flow rate by 40%.

The linear velocity of the mobile phase is a crucial factor in downscaling. The linear velocity expresses how long the mobile phase flows per unit time and is calculated by the equation below. In isocratic mode, the linear velocity can remain constant by changing the flow rate according to the column I.D., and the retention times and the retention patterns also stay the same.