GC is like all chromatographic techniques, based on a multistage distribution process. This process involves a suitable adsorbent (the stationary phase), solvents or solvent mixtures (the mobile phase), and the sample molecules. For Thin Layer Chromatography, the adsorbent is coated as a thin layer onto suitable support (e.g. glass, polyester or aluminium plate), on this layer the substance mixture is separated by elution with a suitable solvent. The most frequently used separation technique is ascending TLC in a glass chamber (standard method, linear development). Usually, it is applied as a single development. However multiple developments, with or without change of mobile phase can improve separation results.