Understanding Retardation Factor in Chromatography
Apr 26, 2025
Retardation Factor in Chromatography
Overview
Retardation Factor (R): Fraction of an analyte in the mobile phase of a chromatographic system.
Planar Chromatography Specifics (RF): Defined as the ratio of the distance traveled by the center of a spot to the distance traveled by the solvent front.
Relation to Retention Factor: Sometimes used synonymously but actually distinct.
General Definition
Formula:
( R = \frac{\text{quantity of substance in the mobile phase}}{\text{total quantity of substance in the system}} )
Represents the fraction of the sample in the mobile phase at equilibrium.
Planar Chromatography
Application: Used in paper chromatography and thin-layer chromatography (TLC).
Formula for RF:
( R_F = \frac{\text{migration distance of substance}}{\text{migration distance of solvent front}} )
RF Value Characteristics:
Always between 0 and 1.
Depends on the polarity of the mobile phase.
Characteristic for each compound under specific conditions.
Used for identification by comparing with known standards on a single plate.
Relationship with Retention Factor
Retention Factor (k):
Defined in column chromatography as the ratio of the time an analyte is retained in the stationary phase to the time in the mobile phase.
Inverse Relationship:
( R = \frac{1}{1 + k} )
( k = \frac{1 - R}{R} )
References
Information adapted from the IUPAC Compendium of Chemical Terminology, specifically regarding terms used in chromatography.