Retention Factor Calculation Formula

Retention Factor in chromatography can be defined as the ratio of distance traveled by solute to the distance traveled by solvent. It is denoted by Rf.

As per USP,

The retention factor of liquid chromatography (also known as mass distribution ratio (Dm) or capacity factor (k′)) is defined as:

k = amount of component in stationary phase / amount of component in mobile phase 

Kc = Vs/Vm


  • Kc = distribution constant (also known as equilibrium distribution coefficient)
  • Vs = volume of the stationary phase
  • Vm = volume of the mobile phase

The retention factor of a component may be determined from the chromatogram using the following equation:

k = (tR−tm)/tm


  • tR = retention time
  • tm = hold-up time

Retention time (tR)

Time elapsed between the injection of the sample and the appearance of the maximum peak response of the eluted sample zone (baseline scale being in minutes or seconds).

Retention volume (VR)

Volume of the mobile phase required for elution of a component. It may be calculated from the retention time and the flow rate (F), in milliliters per minute, using the following equation:

VR = tR ×  F

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