Thin-layer chromatography (TLC) is also an important analytical tool, being used to confirm the progress of reaction, and for evaluation of HPLC separation conditions. Furthermore, the Japanese Pharmacopoeia (JP) has established that the identification tests by TLC must be conducted for many of the natural medicines, such as Scutellaria Root, Phellodendron Bark and Rhubarb, etc. As mentioned, TLC is still an important method of simple separation analysis, which widely used in the many fields.
The Rf-value is a very important piece of data that is provided by TLC. When TLC development conditions are same, the Rf-value is characteristic for a substance. Therefore, the Rf-values are often used for identification of substances. Additionally, selective detection of compounds is possible by choosing the appropriate TLC stains. For example, after development of the TLC plate, if one seeks to identify a compound containing an amino group, the TLC plate is treated with ninhydrin solution which stain only those compounds with an amino group. There are many types of TLC stains reported and used. To obtain accurate results, it is important to select the appropriate TLC stains.
The below table indicates typical TLC stains and the corresponding functional groups. Each of them is prepared so that can be used straight away after the TLC development.