Chromotgraphy TLC + GC APPLICATION

• Why is the separation in TLC not visible to the naked eye?

  Amino acids are colorless, so they need to be made visible by using a developer like ninhydrin or UV.
• How do you calculate the retention factor (Rf) for components in chromatography?

  Use the formula:Rf = (distance moved by component) / (distance moved by solvent front).
• Why must the baseline be drawn in pencil in TLC?

  To prevent the baseline from dissolving into the solvent.
• To prevent the baseline from dissolving into the solvent.

  A capillary tube is used to transfer a small amount of the mixture onto the baseline.
• Why are TLC plates developed in a solvent tank?

  To prevent the solvent from evaporating and becoming a health hazard, to make a saturated atmosphere of the solvent, and to ensure maximum separation.
• What is plotted on the x-axis in gas chromatography?

  Retention time.
• Suggest a suitable gas for the mobile phase in gas chromatography.

  Inert gas such as Nitrogen or helium.
• How can the spectrum in gas chromatography determine the amount of each substance in the mixture?

  The area under the peak is proportional to the amount of that substance in the mixture.
• How can GC be used to identify a substance?

  By matching the retention time with a known substance under the same conditions.
• What is a method for verifying the conclusion from GC analysis?

  Analyze the separated sample using another analytical machine such as an IR spectrometer, mass spectrometer, or NMR machine.
• Why is it essential to wear gloves when handling TLC plates?

  To prevent contamination from skin.
• Why is a pencil line used to mark the solvent front in TLC?


  The solvent line cannot be seen once the solvent evaporates.
• What safety precautions should be taken when using TLC with toxic solvents?

  Allow the complete plate to dry in a fume cupboard, and develop the plate in a developing tank in a fume cupboard
• How can the identity of amino acids be determined from a TLC plate?

  Spray with a developing agent or use UV, measure distances to the spots and solvent front, calculate the Rf value, and compare it with known Rf values UNDER SAME CONDITIONS