Preparative TLC plates have adsorbent layers thicker than the 250 micron layers normally used for analytical separations. Thus, preparative plates can be used for separation of larger quantities of materials.
The loading capacity for a given degree of sample component resolution increases roughly as the square root of the increased adsorbent layer thickness. In preparative TLC, materials to be separated are often applied as long streaks rather than spots. After development, specific compounds may be recovered by scraping the adsorbent layers from the plate in the region of interest and eluting the separated material from the adsorbent using a strong solvent.