In 2D TLC, a sample is first applied to a thin layer of stationary phase, typically a silica gel or alumina-coated plate. The plate is then developed in the first solvent system, which separates the mixture based on certain properties (e.g., polarity). After this initial development, the plate is rotated 90 degrees and developed again in a different solvent system. The two orthogonal developments allow for the separation of components that may overlap in a single development.
