Converting from Flow Velocity to Volumetric Flow Rates

It is convenient when comparing results for columns of different sizes to express flow as flow velocity (cm/h). However, flow is usually measured in volumetric flow rate (mL/min). To convert between flow velocity and volumetric flow rate use one of the formulae below.

From flow velocity (cm/h) to volumetric flow rate (mL/min)

Volumetric flow rate (mL/min) =

Flow velocity (cm/h) 60

× column cross sectional area (cm2)

 

Volumetric flow rate (mL/min) =

Y 60

×

π × d2 4

where

Y = flow velocity in cm/h
d = column inner diameter in cm

Example:

What is the volumetric flow rate in an XK 16/70 column (i.d. 1.6 cm) when the flow velocity is 150 cm/h?
Y = flow velocity = 150 cm/h
d = inner diameter of the column = 1.6 cm

Volumetric flow rate (mL/min) =

150 × π × 1.6 × 1.6 60 × 4

= 5.03 mL/min

From volumetric flow rate (mL/min) to flow velocity (cm/h)

flow velocity (cm/h) =

Volumetric flow rate (mL/min) × 60 column cross sectional area (cm2)

 

flow velocity (cm/h) =

= Z × 60 ×

4     π × d2

where
Z = volumetric flow rate in mL/min
d = column inner diameter in cm

Example:

What is the linear flow in a Tricorn 5/50 column (i.d. 0.5 cm) when the volumetric flow rate is 1 mL/min?
Z = volumetric flow rate = 1 mL/min
d = column inner diameter = 0.5 cm

flow velocity =

1 × 60 ×

4     π × 0.5 × 0.5

= 305.6 cm/h

From volumetric flow rate (mL/min) to using a syringe

1 mL/min = approximately 30 drops/min on a HiTrap 1 mL column
5 mL/min = approximately 120 drops/min on a HiTrap 5 mL column