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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

Materials
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