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| Dyer Scientific and Technical Translations | |
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CHROMATOGRAPHY 1. Introduction 2. Paper Chromatography 3. Thin-layer Chromatography 4. Column/Liquid Chromatography 5. Gas Chromatography 6. High_Pressure Liquid Chromatography 7. Glossary 8. References |
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| Thin-layer Chromatography (Dünnschichtchromatographie) This is very similar to paper chromatography. The stationary phase is applied to a glass or plastic (usually polyester) sheet in a layer about 250 µm thick. The big advantage is that various solids can be used as very fine particles. Silica is very common, and powdered cellulose is often used. With very small and uniform particles, separation is very efficient, and the sheets can be relatively small; I have even seen microscope slides used. Spots are visualized as with paper chromatography, with one addition: silica gel sheets may have an adsorbed fluorescent dye. Then if the material in the spot strongly absorbs ultraviolet light but does not fluoresce, the spot will appear dark on a fluorescent background. When spots have been located, the powder can be scraped off the backing sheet to collect the separated material. Reports/procedures should have the same data as for paper chromatography, plus specification of the plate coating (usually cellulose or silica; perhaps alumina or magnesium silicate ("Florisil"); perhaps the particle size, and any fluorescent indicator).
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