What does the Rf value represent in chromatography?

The Rf value, or Retention factor, in chromatography quantifies the relative distance traveled by a compound compared to the distance traveled by the solvent front. It is calculated by measuring the distance a particular substance has moved from the baseline (the point where the sample was initially applied) divided by the distance the solvent front has moved from the same baseline. This ratio allows for the identification and comparison of compounds based on their movement through the stationary phase in relation to the solvent.

This is particularly significant because different compounds will have different Rf values under the same conditions, allowing for their differentiation. The Rf value remains consistent for a given compound in a specified system, making it a useful tool in chemical analysis. While the other options consider distances or concentrations, they do not encapsulate the comparative nature of the Rf value as a ratio, which is crucial in chromatography.