Thin-layer chromatography principles

See alsa Thin-Layer Chromatography Principles Plate Technology Method Development Instrumentation. 

DESORPTION ELECTROSPRAY lONIZATION-THIN-LAYER CHROMATOGRAPHY PRINCIPLES... 

The on-line principle has also been extended into the field of detection (Fig. 8). Thus, it is now possible to record FTIR [27-31] and Raman spectra in situ [32, 33], and there have been considerable advances in the on-line coupling of thin-layer chromatography with mass spectrometry. Here it has been, above all, the research groups of Wilson [34-36] and Busch [37-40] that have made the necessary instrumental and methodological advances, so that TLC must no longer be viewed as merely a clean-up method. Rather it forms the essential central point for all these on-line coupling techniques. 

It is often possible to increase the selectivity of detection by carrying out a sequence of reactions on one and the same chromatographic plate - a technique that is only possible in thin-layer chromatography. In principle it is possible to distinguish between two sorts of reagent sequence ( TYPE A and TYPE B ), which are discussed in this and the next volume. 

Tswett s initial column liquid chromatography method was developed, tested, and applied in two parallel modes, liquid-solid adsorption and liquid-liquid partition. Adsorption ehromatography, based on a purely physical principle of adsorption, eonsiderably outperformed its partition counterpart with mechanically coated stationary phases to become the most important liquid chromatographic method. This remains true today in thin-layer chromatography (TLC), for which silica gel is by far the major stationary phase. In column chromatography, however, reversed-phase liquid ehromatography using chemically bonded stationary phases is the most popular method. 

Principles and Characteristics High-performance thin-layer chromatography (HPTLC), also known as planar chromatography, is an analytical technique with separation power and reproducibility superior to conventional TLC, which was first used in 1938 [7] and modified in 1958 [8]. HPTLC is based on the use of precoated TLC plates with small particle sizes (3-5 xm) and precise instruments for each step of the chromatographic process. 

We have purposely narrowed the scope of all multidimensional chromatography to those techniques that incorporate separations in the liquid phase and to those in which the use of the comprehensive mode prevails but is not exclusive. This text neither incorporates elements of multidimensional thin-layer chromatography, multidimensional separations in gel media such as those commonly employed for the separation of complex mixtures of proteins, nor the techniques that utilize multidimensional gas chromatography. Some of the same principles apply, particularly in the theory section, but our emphasis is strictly on separations carried out in the liquid phase and by columns, rather than in the gas phase or in planar configurations. 

High-performance thin-layer chromatography (HPTLC) has become widely used and while it follows the same principles as TLC, it makes use of modern technology including automatic application devices and smaller plates, which allow for better sensitivity. 

Rapid method for the identification of the active principles of Cannabis by cir-cular thin-layer chromatography. Boll ChimFarm 1975 114 21. 

Thin layer chromatography (TLC) uses the same principles as GC or HPLC but is performed on a glass plate containing an adsorbent, such as silica or alumina, that attracts other molecules to its surface. A small portion of the sample to be analyzed is spotted on the plate. The plate is placed upright in a tank containing a small amount of solvent that then rises up the plate and separates the components of the sample. The separated components can be located with an ultraviolet lamp or by spraying the plate with chemicals to produce color. 

Thin layer chromatography is in principle similar to paper chromatography when used in the ascending method,... 

Thin layer chromatography is in principle similar to paper chromatography when used in the ascending method, i.e. the solvent creeps up the stationary phase by capillarity. The adsorbent (e.g. silica, alumina, cellulose) is spread on a rectangular glass plate (or solid inert plastic sheet). Some adsorbents (e.g. silica) are mixed with a setting material (e.g. CaSC>4) by the manufacturers which causes the film to set on drying. The adsorbent can... 

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