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
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