TABLE OF CONTENTS Some suppliers have made available channelled silica gel plates for special applications. Channelled TLC plates consist of silica gel tracks, usually 1 cm wide from the top to the bottom of the plate, with spaces of 1 2 mm between tracks. Of course, it is possible to make such channels oneself with a sharp metal point (e.g. a bradawl is quite adequate for the purpose) and a ruler. The width of such channels is therefore decided by the user. Commercially manufactured plate scrapers are also available that enable six channels to be cut on a 10 10 cm glass-backed layer. These units are to be recommended as they give far better precision than the purely manual method. The major advantage of such channels is to prevent the cross contamination of samples that may occur where sample spots are applied close together or where excessive diffusion occurs during development, causing some merging of components. A further advantage is when analyte recovery from the TLC layer is employed. Sections of a channel are much more easily removed without contamination from other separated components on the layer and without damaging other tracks.
