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.

Volumetric ﬂow rate (mL/min) = | Flow velocity (cm/h)60 |
× column cross sectional area (cm^{2}) |

Volumetric ﬂow rate (mL/min) = | Y60 |
× | π × d^{2}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 × 1.660 × 4 |
= 5.03 mL/min |

ﬂow velocity (cm/h) = | Volumetric ﬂow rate (mL/min) × 60column cross sectional area (cm ^{2}) |

ﬂow velocity (cm/h) = | = Z × 60 × | 4 π × d ^{2} |

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 |

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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