Chromatogram development horizontal developing chamber

After a chromatogram has been developed the TLC plate is removed from the developing chamber and the status quo is fixed by removing the mobile phase remaining in the layer as quickly as possible. This is properly performed in the fume cupboard so as not to contaminate the laboratory with solvent fumes. If possible the TLC plate should be laid horizontally because then as the mobile phase evaporates the separated substances will migrate evenly to the surface where they can be the more readily detected. A fan or hair dryer (hot or cold air stream)... 

Isocratic linear development is the most popular mode of chromatogram development in analytical and preparative planar chromatography. It can be easily performed in horizontal chambers of all types. The mobile phase in the reservoir is brought into contact with the adsorbent layer, and then the movement of the eluent front takes place. Chromatogram development is stopped when the mobile phase front reaches the desired position. Usually 20 X 20 cm and 10 X 20 cm plates are applied for preparative separations, and this makes the migration distance equal to about 18 cm. Due to the fact that the migration distance varies with time according to the equation Z, = (Z, c, and t are the distance of the solvent front traveled, constant,... 

FIGURE 6.13 Schematic demonstration of horizontal DS chamber application for continuous development (a) cross section of DS chamber during continuous development, (b) part of the plate with bands of lower retention exposed but with bands of higher retention covered to enable further development, (c) final chromatogram. 

As mentioned earlier, the preceding chromatogram development on the full length of the 20-cm plate takes a lot of time. To overcome this problem, the development of chromatogram on a short distance with simultaneous evaporation of the mobile phase from the exposed part of the chromatographic plate can be very conveniently performed by means of horizontal chambers. The mode was introduced by Perry [23] and further popularized by Soczewinski et al. [24,26], using a horizontal equilibrium sandwich chamber. 

The possibility of zonal sample dosage in equilibrium conditions (after the front of mobile-phase and continuous-chromatogram development, which is provided by a horizontal sandwich chamber) was utilized by Glowniak et al. [3] in preparative chromatography of simple coumarins and furano-coumarins found in Archangelica fruits, performed with a short-bed continuous development (SB-CD) technique. 

In the DAB method, the identity test for camomile flowers is also performed using chloroform p.f.a. (DAB nomenclature chloroform R) as the solvent. Even the very low percentage of water in the stabilizer present (ethanol) can lead to the formation of a (3-front on development (Fig. 44a). If, on the other hand, the chloroform is dried over sodium sulfate shortly before placing it in the developing chamber, a thin-film chromatogram without an interfering (3-front is obtained, as shown in Fig. 44b [46]. This example could not be repeated reproducibly, and probably only happens with the 5 x 5cm horizontal chamber (see Section 4.2.1.2). 

Chloitetracycline, 468-472 Cholecalciferol (vitamin Da), 1061 Chromatogram development, 135-140 automated multiple development, 138-140 automatic chromatogram development, 138 general aspects of development, 135-137 horizontal developing chamber, 138 in a tank, 137-138 Chromatorods, 362 Chromatostrips, 362... 

Conventional thin-layer chromatography (TLC) in our experience, known under the name planar chromatography, uses horizontal or vertical glass or Teflon chambers for the development of chromatograms. As stationary phases, commonly known adsorbents or supports based on silica gel, aluminium oxide, magnesium silica, cellulose, and so forth are used particle sizes are about 20 jitm. The migration of the mobile phase is based on the phenomenon of capillary forces. This chromatographic method is described, in detail, in other sections of this volume. 

Samples (20 /xl) were applied as 6-8 mmbands by means of a Camag automatic TLC Sampler III. Chromatograms were developed face down in a horizontal Teflon DS chamber and saturated before use for 15 min, at room temperature, to a distance of 9 cm. 

---