Chromatography

• What is chromatography?

  An analytical technique for separating mixtures
• What are the two phases involved in chromatography?

  Mobile phase and stationary phase
• What can the mobile phase be in chromatography?

  A liquid or a gas
• How does a solid stationary phase separate components?

  By adsorption
• How does a liquid stationary phase separate components?

  By relative solubility
• What happens if the stationary phase is polar and the mobile phase is non-polar?

  Non-polar compounds pass through quickly
• What does separation by column chromatography depend on?

  Balance between solubility and retention
• What is the mobile phase in gas-liquid chromatography (GC)?

  An inert gas like nitrogen or helium
• What is the stationary phase in gas chromatography?

  A liquid on an inert solid
• What are the types of chromatography?

  • Thin-layer chromatography (TLC)
  • Column chromatography (CC)
  • Gas chromatography (GC)
• What is the purpose of retention times and Rf values in chromatography?

  To identify different substances
• What are the steps in thin-layer chromatography (TLC)?

  1. Draw a pencil line on the TLC plate
  2. Add drops of each solution
  3. Place in a solvent chamber
  4. Remove and mark solvent level
  5. Dry the plate and visualize under UV
  6. Calculate Rf values
• What is the formula for calculating Rf values?

  Rf = distance moved by amino acid / distance moved by solvent
• Why should gloves be worn during TLC?

  To prevent contamination from hands
• Why is a pencil line used in TLC?

  It will not dissolve in the solvent
• What happens if the solvent depth is too deep in TLC?

  It will dissolve the sample spots
• What is the purpose of drying the TLC plate in a fume cupboard?

  To avoid exposure to toxic solvent
• What is two directional chromatography used for?

  To separate complex mixtures with different solubility
• How is two directional chromatography performed?

  Using two different solvents in sequence
• What does HPLC stand for?

  High performance liquid chromatography
• What is the stationary phase in HPLC?

  A solid silica
• What are the steps in simple column chromatography?

  1. Fill a glass tube with stationary phase
  2. Add a filter to retain the solid
  3. Cover with solvent
  4. Dissolve the mixture in a minimum solvent
  5. Run solvent through the column
  6. Record retention times
• What is the purpose of gas-liquid chromatography?

  To separate mixtures of volatile liquids
• What is the mobile phase in gas-liquid chromatography?

  An inert gas like helium
• What is the significance of retention time in gas-liquid chromatography?

  It helps identify a substance
• How can gas-liquid chromatography indicate the number of components in a mixture?

  By the number of peaks in the output
• What does the area under each peak in gas-liquid chromatography represent?

  Proportional abundance of each component
• What is GC-MS used for?

  Analysis in forensics and environmental studies
• What factors can change retention times in gas-liquid chromatography?

  Temperature, column length, and flow rate
• What happens if the temperature or flow rate is increased in gas-liquid chromatography?

  Substances move more quickly, shorter retention times
• Why is it important to use an inert carrier gas in gas-liquid chromatography?

  It does not react with separated components