Thin-layer chromatography separation chambers

Geiss, F., and Schlitt, H, (1968). A new and versatile thin layer chromatography separation system (KS-Vario-Chamber). Chromatographia I 392-402. 

There is no other facet where thin-layer chromatography reveals its paper-chromatographic ancestry more clearly than in the question of development chambers (Fig. 56). Scaled-down paper-chromatographic chambers are still used for development to this day. From the beginning these possessed a vapor space, to allow an equilibration of the whole system for partition-chromatographic separations. The organic mobile phase was placed in the upper trough after the internal space of the chamber and, hence, the paper had been saturated, via the vapor phase, with the hydrophilic lower phase on the base of the chamber. 

Fig. 20 Schematic representation of an eiectric spark discharge chamber for the activation of gases at normal atmospheric pressure for the production of fluorescence in substances separated by thin-layer chromatography [2],...

Van de Vaart et al. [45] used a thin-layer chromatographic method for the analysis of miconazole and other compounds in pharmaceutical creams. The drugs in creams were analyzed by thin-layer chromatography on silica gel plates with ether in pentane-saturated chamber or with butanol-water-acetic acid (20 5 2). Both active ingredients and vehicle components were detected and Rf values of 67 active ingredients are tabulated. Additional eluents may be needed to separate certain combinations of ingredients. 

The procedure of paper and thin-layer chromatography. A Application of the sample. B Setting plate in solvent chamber. C Movement of solvent by capillary action. D Detection of separated components and calculation of Rf. 

There are two popular LC techniques in which the stationary bed is supported on a planar surface rather than in a column paper chromatography (PC) and thin-layer chromatography (TLC). PC preceded TLC by some 10 to 15 years, and a large number of excellent separations were devised for it. But beginning about 1956, it was found that TLC could also be used for most of these separations and that it was faster, more reproducible, more versatile, and more convenient. As a result, most laboratories have abandoned the use of PC with its large cumbersome glass chambers. Those who have not, continue to use PC because they feel that the original PC methods are superior or because of the lower cost of PC. 

Thin layer chromatography (TLC) A chromatographic technique employing a porous medium of glass coated with a stationary phase. An extract is spotted near the bottom of the medium and placed in a chamber with solvent (mobile phase). The solvent moves up the medium and separates the components of the extract, based on affinities for the medium and solvent. 

Figure 12.1 Thin-layer Chromatography (a) Device for spreading a layer of adsorbent (b) Chamber for chromatographing with a solvent (aluent) at the bottom (c) A developed plate showing mixture (A+B) having separated into its constituents B and A spots marked (A+B), B and A on the starting line refer to those of the mixture and known compounds B and A respectively.

Equipment used for thin-layer electrophoresis is practically the same as that used for separations on paper, cellulose acetate and ion exchange papers. Usually cooling is introduced into the equipment. Thus, e.g., a water-cooled flat aluminium (dural, brass) block is insulated by means of a replaceable glass plate or plastic film. The thin-layer plate is located on the insulated block and paper wicks ensure the contact with electrode vessels. A polyethylene sheet is placed between the top of the layer and the lid. This protects the surface of the layer from drops of condensed moisture that condense on the lid. A sheet of plate glass covers the whole chamber. If precoated plastic thin-layer sheets are used, the apparatus of the immersed type can be used [78]. Elution of spots, and the general practice in thin-layer electrophoresis is the same as in thin-layer chromatography. 

Thin-Layer Chromatography Coupled with Fluorometry. Aliquots of the prepared samples stored in the pear-shaped flasks are spotted on the thin-layer plates. The development of these plates for separation of the individual compounds can be done in one or two directions which takes place in an equilibrated chamber first with a mixture of toluene/n-hexane/n-pentane (5 90 5) to a distance of 15-16 cm. After drying, the plates are developed in the second direction with a mixture of methanol/diethyl ether/water (6 4 1). A typical two dimensional TLC of a PAH standard is shown in Figure 3. 

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