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How long does the feed spend in the column?

Chromatography residence time, linear velocity and load calculator

From the size of a packed column and the flow rate, works out how long the liquid stays in the resin bed (residence time), how fast it moves (linear velocity) and how much you can load per cycle.

When to use itUse it when setting conditions for antibody capture on Protein A or similar columns, or when transferring conditions from a small column to a large one.

Prefilled with an example: a 20 mL column with a 20 cm bed, run at 5 mL/min. Change any value and the result updates.

cm

The height of the packed resin inside the column.

mL

The volume of the packed resin bed. 1 mL equals 1 cm³.

mL/min

The volume pumped per minute.

mg/mL resin

Binding capacity measured under flow. Check the condition it was measured at, such as 10% breakthrough (QB10%).

Time in the resin bed (residence time)4 min
Linear velocity300 cm/h
Load per cycle800 mg

The liquid takes about 4 minutes to pass through the resin, and this column can take up to about 800 mg of antibody. That is within the few-minute range where Protein A loads well.

Residence time guide (Protein A)

The row that matches your result is marked.

  • Under 1 minuteShort (fast flow)Antibody tends to pass before it can diffuse deep into the resin beads, so the capacity you can use (DBC) tends to drop. Our related article also notes that faster flow lowers DBC. Where too short begins depends on the resin and the antibody.
  • 1 to 6 minutesYour resultA few minutes (good loading range for Protein A)With Protein A, a residence time of a few minutes tends to increase the amount captured. The best range depends on the resin and antibody, so it is not a single standard.
  • Over 6 minutesLong (more capacity, more time)Longer residence lets you load more, but each cycle takes longer and throughput per hour (productivity) falls. Decide on the balance between yield and productivity.

How it is calculated

Residence time = resin volume ÷ flow rate, and linear velocity = flow rate ÷ column cross-section × 60 (cross-section = volume ÷ height). When scaling up a column you usually keep the bed height and linear velocity and widen only the diameter. The residence time then stays the same.

residence time = CV ÷ flow rate linear velocity [cm/h] = flow rate × bed height ÷ CV × 60 load = DBC × CV

Source: Residence time is column volume ÷ flow rate, and linear velocity is flow rate ÷ cross-sectional area. These are basic chromatography relationships (see, for example, Cytiva's chromatography handbooks).

With your numbers

  1. residence time = column volume ÷ flow rate = 20 ÷ 5 = 4 min
  2. linear velocity = (flow rate × bed height ÷ column volume) × 60 = 300 cm/h
  3. column load = DBC × column volume = 40 × 20 = 800 mg

Limits of this calculation

  • The equations for residence time, linear velocity and load are established standard definitions. DBC values, however, can only be compared if they were measured under the same conditions: breakthrough criterion (QB10% or QB1%), antibody concentration in the feed, system corrections and residence time.
  • Load = DBC × volume approximates the antibody captured up to 10% breakthrough when run under the same conditions as the DBC measurement. It is a simple equation that does not subtract what leaks during loading, so it tends to overestimate.
  • The guide of a few minutes varies with resin and antibody and is not a single reference value. The guide above puts the trend described in our related article into words; it is not a specification.
  • Linear velocity assumes a cylindrical column of uniform cross-section. The cross-section is derived from volume and height, taking 1 mL = 1 cm³.
  • DBC measured under flow is normally lower than the static binding capacity (SBC) measured without flow, because diffusion into the beads cannot keep up. Loading is set from DBC as a rule.

Primary sources

Every calculator gives an estimate for learning, built on published information and primary sources. Real decisions follow the applicable guidance and expert judgment.