thin layer chromatography description analysis
- 1. Chapter 8 Chapter 8 Thin-Layer Chromatography Thin-Layer Chromatography
- 2. Thin-Layer Chromatography (TLC) Thin-Layer Chromatography (TLC) TLC is a fast, simple, and inexpensive TLC is a fast, simple, and inexpensive analytical technique used to determine or analytical technique used to determine or monitor: monitor: - - The # of components in a mixture. The # of components in a mixture. - - The identity of two substances. The identity of two substances. - - The effectiveness of a purification. The effectiveness of a purification. - - The appropriate conditions for a column The appropriate conditions for a column chromatographic separation. chromatographic separation. - - The progress of a reaction. The progress of a reaction. - - Column chromatography effectiveness. Column chromatography effectiveness.
- 3. • TLC involves spotting a dilute solution (1%) of TLC involves spotting a dilute solution (1%) of sample on one end of a small sheet that has been sample on one end of a small sheet that has been coated with silica gel (SiO coated with silica gel (SiO2 2) or alumina (Al ) or alumina (Al2 2O O3 3), ), known as the stationary adsorbent phase. known as the stationary adsorbent phase. • The sheet is placed upright inside a jar in a small The sheet is placed upright inside a jar in a small pool of solvent. As the solvent rises up the sheet by pool of solvent. As the solvent rises up the sheet by capillary action, the components travel at different capillary action, the components travel at different rates based on competing interactions with the rates based on competing interactions with the mobile (solvent) and adsorbent phases. mobile (solvent) and adsorbent phases. • SiO SiO2 2 is used for separation of more polar is used for separation of more polar compounds while Al compounds while Al2 2O O3 3 is used in the separation of is used in the separation of non-polar compounds. non-polar compounds. Thin-Layer Chromatography (TLC) Thin-Layer Chromatography (TLC)
- 4. Thin-Layer Chromatography (TLC) Thin-Layer Chromatography (TLC) • A polar solvent will carry a polar compound A polar solvent will carry a polar compound farther while a non-polar solvent will carry a non- farther while a non-polar solvent will carry a non- polar compound farther. polar compound farther. • R Rf f value is the ratio of the distance the spot travels value is the ratio of the distance the spot travels from the origin to the distance the solvent travels. from the origin to the distance the solvent travels.
- 5. Comments Comments • Do not let the plate sit in the solvent chamber after Do not let the plate sit in the solvent chamber after the solvent front reaches the top of the plate. the solvent front reaches the top of the plate. Why? Why? • When spotting, the solution typically adsorbs very When spotting, the solution typically adsorbs very quickly and the spot can easily get larger than quickly and the spot can easily get larger than desired (1 mm diameter). desired (1 mm diameter). • Make 3-4 lanes on each plate, marked with pencil Make 3-4 lanes on each plate, marked with pencil and ruler and experiment with large and small and ruler and experiment with large and small spots to find which works best. spots to find which works best. • Record the R Record the Rf f values for each substance. values for each substance. • Follow lab handout for all experimental Follow lab handout for all experimental procedures. procedures. • Keep the layer of liquid with the most color. Keep the layer of liquid with the most color. • Do not evaporate the dichloromethane solution Do not evaporate the dichloromethane solution
- 6. • Solvents used are flammable, use Solvents used are flammable, use caution caution • Separation of components should be Separation of components should be easy to distinguish. easy to distinguish. • Answer questions Answer questions: 2, 3 (p : 2, 3 (p. . 1 192 92) ) Comments Comments