Thin Layer Chromatography

Making TLC Plates from Bulk TLC Silica Gels
Many TLC users prefer to use pre-coated TLC plates, but others because of their special needs, or because they need special additives or a special thickness, coat their own TLC plates. This paper is a quick review of what is needed for the process.

Initial instructions for plate coating:
If reproducible plates are needed, then the user should invest in a coating device from Camag or Desaga (addresses below). The devices consist of a tray that holds the glass plates, and a device that holds the slurry to be placed on the glass plates. A guide allows the applicator (with an adjustable layer thickness gauge) to be pulled along the glass plates as the slurry is dispensed. Some practice is needed to get a continuous body motion pulling the applicator across the plates to get an even layer. The glass plates must be the same thickness and extremely clean. Any oil or grease will result in a poor layer. Handle the plates with rubber gloves when washing or rinsing. Care is also needed if the edges of these plates are not polished or finished off, since a serious cut might result. If only coating one or two plates, then a glass plate can be built up on two opposite edges with masking tape to an appropriate height to give the thickness needed. Slurry is poured on to one end of the plate and a glass rod that extends past the masking taped edges can be used to pull the slurry evenly over the plate. There will be considerable waste until the correct amount of slurry for the thickness required is figured out from trial and error. Smaller TLC plates can be coated by using smaller glass plates (microscope slides) and placing two of them back to back. The two slides are dipped into the silica (or other) slurry, pulled out, separated and dried. If a small beaker is used and methanol instead of water is used for the slurry, then the silica gel slurry can be saved and used again.

Binders and TLC:
It is important that anyone making TLC

References: 1) E. Stahl, Thin Layer Chromatography, Springer-Verlag, New York, 1969 2) Camag Scientific, Inc., 515 Cornelius Harnett Drive, Wilmington, NC 28401, phone [phone], fax [phone]) Desaga GmbH, P.O. Box 101969, D-69009 Heidelberg, Germany, phone [phone], fax [phone]