Development Techniques

Adsorbents used in TLC may be either commercial products or home-made plates (now seldom employed). High quality chromatograms can be achieved with HPTLC plates which were introduced in the 1980s.

Plates may be developed in a linear, circular or anticircular mode. The most common technique in TLC of alkaloids is ascending, single, one-dimensional development in tanks saturated with the vapour of the solvent system.

Preconditioning the plate with the vapours, thus preventing demixing of the mobile-phase components, can also be performed in sandwich-type chambers produced by Camag (Vario-KS) and Chromdes (DS). In some cases, especially where compounds differ in polarity, repeated development of the plate with the same solvent or solvents of increasing strength or the continuous development technique has some advantages. In other cases, programmed multiple development with the same solvent may be successfully applied. Also useful is two-dimensional development, which is especially valuable for separating a greater number of alkaloids in a given section of the plant.

Great differences in the polarity of alkaloid molecules make gradient elution advantageous. This technique may be developed in both glass chambers and in horizontal chambers as well as with overpres-sured layer chromatography.

Worth noticing is one technique related to TLC - thin-layer electrophoresis, which has been used as a two-dimensional combination with TLC for the separation of ergot alkaloids.

Solar Panel Basics

Solar Panel Basics

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