Principles and Practice of Chromatography - Thin Layer Chromatography Apparatus > Continuous Plate Development > Page 65

Plate Saturated by Solvent Unsaturated Plate

Vapor

Figure 31 Effect of Plate Saturation on Plate Development

Continuous Plate Development

The normal development of a thin layer plate is limited by its physical dimensions but a continuous development procedure has been used employing special equipment. An apparatus used for the continuous development of a thin layer plate is shown in figure 32.

The plate is held horizontal and inverted so that the stationary phase layer faces downwards and rests on a second glass cover plate. A wick transfers the solvent from the reservoir to the stationary phase coating which is sandwiched between the two glass plates. The whole system is situated in a suitable chamber to prevent solvent evaporation from the reservoir. The solvent passes along the plate by surface tension forces in the usual way until it reaches the end of the plate. A small area at the end of the plate is exposed and heated electrically to evaporate the solvent as it arrives. In this way development can be continued and the system now resembles an LC column of lamina shape. The value of this technique is a little questionable as its intent is to simulate an LC column, in which case it would be preferable to use an LC column in the first place.

Figure 32 Apparatus for the Continuous Development of a Thin Layer Plate