The Retardation Factor ($R_f$) is a ratio used to identify substances in chromatography (TLC or Paper).

• Calculation: $R_f=\frac{\text{Distance traveled by the substance from the base line}}{\text{Distance traveled by the solvent front from the base line}}$
• Properties:
• The $R_f$ value is always between 0 and 1.
• It is a characteristic constant for a particular compound in a specific solvent system and stationary phase, enabling qualitative identification.