Chromatogram development

Note If the chromatogram developed by method B was exposed to ammonia vapors for 10 min before being immersed in liquid paraffin— -hexane (1 -I- 2) the fluorescence of the chromatogram zones became deep red. Glucose and fructose also appeared red. 

Regarding development, normal sdica gel layers are tried first if not otherwise indicated. Selection of the best developing solvent has to be performed systematically, and its preparation should be proper. Various modes of development and separation chambers, both of which can influence the separation, have to be considered for development, with focus on the classical method of chromatogram development. Aspects of the chamber climate are helpful as background information and can improve resolution. 

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,... 

This mode of chromatogram development is, in principle, almost identical with continuous development. The only feature that varies is the length of the developing path. In short bed-continuous development (SB/CD), this path is very short, typically equal to several centimeters [23-25]. This is the reason why this mode is preferentially applied for analytical separations. However, a similar technique is applied for zonal sample application and online extraction of solid samples, which are described in the following text. 

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. 

All these modes of mnltiple chromatogram development are mainly apphed in analytical separation however, there are some examples of preparative planar chromatography [31,32]. 

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