Retardation factor
The retardation factor, also known as retention factor or Rf value, represents the characteristic rate of movement of a component in a mixture as the mobile phase moves. The Rf value is different for different compounds. The Rf value depends on:
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The nature of the compound
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The mobile phase used
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The temperature
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The presence of impurities
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The quality of the paper or TLC plate (the stationary phase)
The Rf value can be determined by the following equation:
Since the solvent front always moves faster than the components, the Rf value will always be less than 1. The Rf value has no units.
The Rf value is not to be confused with the retention factor k', also known as the capacity factor.
References:
- NCERT Chromatography handbook