thin-layer chromatography (TLC)

Type of chromatography using as the stationary phase a thin layer (0.01 inch [0.25 mm]) of a special finely ground matrix (silica gel, alumina, or similar material) coated on a glass plate or incorporated in a plastic film. Solutions of the mixtures to be analyzed are spotted near one edge. Solutions of reference compounds are similarly applied. The edge of the plate is then dipped in a solvent. The solvent travels up the matrix by capillarity, moving the components of the samples at various rates because of their different degrees of attachment to the matrix and solubility in the developing solvent. The components, visible as separated spots, are identified by comparing the distances they have traveled with those of the known reference materials. TLC is useful for biological mixtures, especially lipids in animal or vegetable tissues and isoprenoids and essential oils found in flowers and other parts of plants. The matrices withstand strong solvents and developers better than the paper used in paper chromatography.