Thin Layer Chromatography (TLC) is a solid – liquid form of chromatography where the stationary phase is normally a polar absorbent and the mobile phase can be a single solvent or combination of solvents.
In thin layer chromatography, the stationary phase is a polar absorbent which finely ground alumina or silica particles. This absorbent is coated on a glass slide or plastic sheet creating a thin layer of the particular stationary phase. Almost all mixtures of solvent can be used as the mobile phase. By manipulating the mobile phase, organic compounds can be seperated.
The ratio of the distance the spot travels to the distance the solvent travels is called the Rf (retardation factor) value. The figure 1 below illustrates how to calculate the Rf value
Rf = distance moved by center of spot / distance moved by solvent front
Reference: Thin Layer Chromatography, Material of the introduction General Biology Labwork 1, Faculty of Biology & Biotechnology, University of Science, VNUHCM.