Thin Layer Chromatography
Sketch each of your TLC plates. Indicate:
the origin (starting position) of each spot
the final solvent front
the solvent in which the plate was developed
the method(s) of visualization.
Calculate Rf values for each spot; present these data in a Table.
- Discuss the theory of the TLC experiment. Why do different compounds move different amounts up the TLC plate? What forces are involved here? (You may wish to think about molecular polarity and read about hydrogen bonding beginning on pages 659, 818, 982 and 1165 in McMurry.)
- Do more polar or less polar compounds travel farther up (have a higher Rf on) a silica gel TLC plate?
- For the same compound on a silica gel TLC plate, will a more polar or a less polar solvent move it farther up the plate (higher Rf)?
- Describe the TLC of the analgesics. Could you clearly see each compound? Were all the spots in the reference mixture clearly defined? Which compound was the most/least polar?
- What analgesic(s) was(were) contained in the unknown tablet? What information did you use to identify the tabletís active ingredients?
- Describe the TLC of the benzoate esters. Which solvent did you develop the chromatogram in? Why? Comment on how the TLC results changed as you changed the developing solvent. Which of the benzoate esters was the most/least polar?
- What important technique issues should be considered when running TLC? Were your spots too big, too small, streaky? Under what conditions were your best results obtained?