Residence time calculator
Residence time from bed volume and flow rate — or the flow rate you need for a target residence time. Works for packed columns, monoliths and membrane devices.
Preset flow rates are the datasheet values; the recommended range is 5–10 MV/min.
15 mL/min · 8.33 MV/min
The volume of the packed bed, not the hardware.
1.25 mL/min · 0.25 CV/min
At these settings the product spends 7.2 s in the capsule and 4 min in the column — 8.33 MV/min against 0.25 CV/min. Residence time is what the two beds do differently; the method itself does not have to change.
Residence time = bed volume ÷ volumetric flow rate. Click the unit next to a flow rate to switch between mL/min and bed volumes per minute. The calculation does not check whether a flow rate is within the pressure limit of your column, capsule or system, and it says nothing about binding capacity at that residence time — both belong to the datasheet of the medium.
Linear velocity ↔ flow rate converter
For packed columns the flow is often given as a linear velocity in cm/h, because it stays constant when a method is scaled to a wider column at the same bed height. Convert it here in either direction — it applies to a cylindrical packed bed, not to a capsule.
Linear velocity describes flow through a cylindrical packed bed of a given height, so it applies to a column rather than to a capsule. For a monolith, flow is expressed in monolith volumes per minute instead — the two are not interchangeable.
How residence time is calculated
Residence time (RT) is the time a volume of liquid spends inside the chromatography bed. It follows directly from the bed volume and the volumetric flow rate:
Its inverse is the number of column volumes that pass per minute (CV/min). A residence time of 0.5 min means 2 CV/min; 2 min means 0.5 CV/min. A MonoCore™ Q capsule with 1.8 mL bed volume is run at a recommended 15 mL/min — a residence time of about 7 seconds, or roughly 8 MV/min, within the recommended range of 5 to 10. The 5.4 mL format runs at 45 mL/min with the same residence time.
Packed columns: bed height and linear velocity
For packed-bed columns the flow is usually given as linear velocity u in cm/h, because it stays constant when a method is scaled to a wider column at the same bed height. Residence time then is:
The converter above moves between linear velocity, volumetric flow and bed volume in either direction.
Residence time in convective media
In porous resin beads, most binding sites sit inside the pores. Target molecules reach them by diffusion, and diffusion is slow for large molecules such as antibodies, plasmids or viral vectors. This is why packed beds are typically operated at residence times of several minutes, and why their dynamic binding capacity tends to fall when the flow is increased. That relationship is why a capacity figure without its residence time cannot be compared between media — see how to read a dynamic binding capacity figure.
Monoliths and membrane adsorbers work differently: the liquid is pushed through open channels, and the target is carried to the binding sites by convection. MonoCore™ is a modified cellulose monolith with 15 µm channels, supplied as a drop-in capsule with UNF 10/32 connections for standard FPLC systems. The background is explained in convective vs. diffusive mass transport.
What this calculator does not tell you
It does not check pressure. Whether a flow rate is feasible depends on the pressure limit of the column or capsule, the viscosity of your feed and the pressure rating of your system. Check the datasheet of the device you use before running at a new flow rate.
Frequently asked questions
How do you calculate residence time in chromatography?
Residence time is the bed volume divided by the volumetric flow rate: RT = V / Q. A 1.8 mL MonoCore™ capsule run at its recommended flow rate of 15 mL/min has a residence time of 0.12 min (about 7 s), which equals roughly 8 column volumes per minute. For a packed column you can also use bed height divided by linear velocity: RT = L / u.
What is the difference between residence time and retention time?
Residence time describes the flow: how long a volume element of liquid needs to pass through the bed. Retention time describes a molecule: how long it takes until it elutes, which depends on how strongly it binds. Residence time is set by the operator via the flow rate; retention time is the result of the separation.
Why does residence time matter for binding capacity?
In porous beads, target molecules must diffuse into the pores before they can bind. At short residence times there is less time for diffusion, so the dynamic binding capacity of a packed bed usually drops as flow increases. In convective media such as monoliths and membranes, the liquid is pushed through open channels past the binding sites, which is why these formats are designed to be run at much shorter residence times.
Should I use linear velocity or volumetric flow for a monolith?
Linear velocity (cm/h) is the scale-up parameter for packed columns with a defined bed height. Monolith capsules and membrane devices do not have a simple axial bed, so their flow is specified volumetrically — as mL/min or column volumes per minute (CV/min). Use the first calculator on this page for capsules, the second for packed columns.
How do I convert linear velocity (cm/h) to flow rate (mL/min)?
Multiply the linear velocity by the column cross-sectional area and divide by 60: Q [mL/min] = u [cm/h] × π × (d/2)² [cm²] / 60. A 1.6 cm inner-diameter column at 300 cm/h runs at about 10 mL/min.