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

Appendix 4 extracted from Affinity Chromatography Principles and Methods, GE Healthcare, 2007

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) x column cross sectional area (cm2) 60

 = Y × π x d2 60 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 ml/min 60 × 4

= 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

where
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 cm/h π x 0.5 x 0.5

= 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