Thin Layer Chromatography - Summary 2
The use of radioactive tracers introduces alternative procedures for scanning a thin layer plate. One method, called contact radiography where, after development and drying, the plate is placed in contact with a photographic plate or film for a day or two. The film is developed and the spots caused by the radiation then scanned in the usual manner. Alternatively, the plate can be scanned with a radioactive counter-scanner and the radio chromatogram produced directly. This technique can be highly sensitive and at the same time appears to give good precision and accuracy. Pressurized thin layer chromatography, where the flow is energy-driven instead of by surface tension forces can provide better resolution and shorter analysis times. However, the accuracy and precision obtained form such techniques appear little better than those obtained from conventional thin layer chromatography. An interesting development of the thin layer technique is to first use the plate as a synthesis medium to produce the products of interest. The plate is then used to separate the products in the conventional manner. Finally the individual spots on the plate are used to test the biological activity of each separated component.