Question

2. What are the phases involved in TLC? 3. What is coated on the TLC plate? 4. What is the purpose of lining the wall of the TLC chamber with paper? 5. Why is it important to use a small amount of the mobile phase? 6. Why should you remove the TLC plate before the mobile phase reaches the top? 7. What type of compounds are visible with UV light? 8. With a polar stationary phase and non-polar mobile phase, rank the following compounds in order of lowest Rivalue to highest. 9. Why should you not use a pen to draw on your TLC plate?

Answer 1

2. The phases involved in TLC (thin layer chromatography) are stationary phase (solid) and mobile phase (liquid).

3. Coatings used in the TLC plates are- silica gel and alumina gel.

4. Paper absorbs solvents and initiate evaporation process. More evaporation means more solvent vapour inside the TLC chamber which is desirable.

5. It is important to maintain a perfect solvent line so that the reference line must not get submerged into the solvent otherwise the spots will start running downwards into the solvent. This would contaminate the solvent and experiment will fail. The solvent line should be slightly lower than the reference line of TLC.

6. TLC plates should be removed before the mobile phase runs to the top because that would not let us decide on the products containing in the substance. Any polar product would run into the top and if let to run the entire plate and hence we could miss it's existence and get a wrong inference. It is suggested to run the TLC 90% of its length.

7. Usually the compounds undergoing electronic transition and energy gap between ground state and exited state are in UV range are visible in UV light.