Planer chromatography techniques like paper chromatography (PC) and thin layer chromatography (TLC) separate compounds based on their differential migration rates through a stationary phase. In PC, the stationary phase is a sheet of paper and separation occurs as solvent moves up the paper. In TLC, a thin layer of adsorbent like silica gel is coated on a plate and separation occurs as solvent moves across the plate. The degree of retention is expressed as Rf value, which is the ratio of the distance traveled by the compound to the distance traveled by the solvent front. Planer chromatography has applications in qualitative, quantitative, and preparative analysis and is useful for isolating and purifying compounds.