Thin Layer Chromatography - Purity Measurements of Phthaloyl-Amiodipine Using Over Pressurized Thin Layer Chromatography 3


Significant advances in the technique of thin layer chromatography have been few and far between over the last decade but, nevertheless, progress continues, albeit at a reduced rate. A particularly interesting application was described a few years ago which involved a procedure that combines synthesis, separation, quantitative analysis and biological screening, consecutively carried out on a thin layer plate. This technique is particularly applicable to combinatorial chemistry and has been reported by Freemantle (19). Details of the method have been described by Williams (20), an example of which is given as follows. Parallel syntheses were carried out in a series of spots on the baseline of a TLC plate coated with silica; the reaction was accelerated by heat, employing microwave irradiation. Different synthetic conditions were employed for each spot in order to determine the optimum conditions for the synthesis. The products were then separated by developing the plate with an appropriate solvent and a quantitative assessment carried out on each pertinent spot by suitable scanning techniques or visual comparison of the spots with a standard. Each spot was then screened in situ for microbial growth inhibition or other biological activity by standard agar-overlay procedures carried out directly on the plate. The value of this approach in combinatorial synthesis is clearly obvious as many different synthetic conditions can be investigated simultaneously and the biological activity of the products concurrently ascertained. This procedure is quite unique and is an excellent illustration of the extension of an ongoing and established technique to a challenging modern chemical problem.