In chromatography, the Rf value represents the ratio between the migration distance of a substance and the migration distance of the solvent front. Rf is a coefficient called retention factor and has values that range between zero and 1.
Rf quantifies the distance that each compound of the analyzed mixture has traveled. The higher the Rf value, the longer the distance that a specific compound has traveled. The solvent front always moves further than any of the compound in the mixture. However, the compounds migrate differently depending on the type of mobile phase used because the migration speed depends on some characteristics of the solvent, such as polarity. The Rf value is characteristic for any chemical compound.