Converting From Linear Flow (cm/hour) to Volumetric Flow Rates (mL/min) and Vice Versa

It is convenient when comparing results for columns of different sizes to express flow as linear flow (cm/hour). However, flow is usually measured in volumetric flow rate (mL/min).

To convert between linear flow and volumetric flow rate use one of the formulae below.

From linear flow (cm/hour) to volumetric flow rate (mL/min)

Volumetric flow rate (ml/min) =

Linear flow (cm/h) 60

x column cross sectional area (cm2)

=

Y 60

×

π x d2 4

where
Y = linear flow 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 linear flow is 150 cm/hour?
Y = linear flow = 150 cm/h
d = inner diameter of the column = 1.6 cm

Volumetric flow rate (ml/min) =

150 × π × 1.6 x 1.6 60 × 4

mL/min

= 5.03 ml/min

From volumetric flow rate (mL/min) to linear flow (cm/hour)

Linear flow rate =

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

= Z × 60 ×

4 π x d2

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

Example:
What is the linear flow in an HR 5/5 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

Linear flow = 1 × 60 ×

4 π x 0.5 x 0.5

cm/h

= 305.6 cm/h

From 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