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
• What types of stationary phases are used in chromatography?

  A solid or a liquid on a solid support
• 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 in column chromatography depend on?

  Solubility in the moving phase 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-liquid chromatography (GC)?

  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 is the first step in thin-layer chromatography (TLC)?

  Draw a pencil line on the TLC plate
• Why should the pencil line be above the solvent level in TLC?

  To prevent dissolving the sample spots
• What is the purpose of wearing gloves during TLC?

  To prevent contamination from hands
• What should be done if the solvent is too deep in TLC?

  It will dissolve the sample spots
• What is the formula for calculating Rf values?

  Rf = distance moved by amino acid / distance moved by solvent
• Why is a UV lamp used in TLC?

  To see colorless spots on the plate
• What is two directional chromatography?

  • Uses two different solvents
  • First separation with one solvent
  • Rotate plate 90° for second solvent
  • Helps separate complex mixtures
• What does HPLC stand for?

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

  A solid silica
• What is the mobile phase in HPLC?

  A liquid
• What are the steps in simple column chromatography?

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

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

  The time for a compound to travel to the detector
• How can gas-liquid chromatography identify substances?

  By analyzing retention times and peaks
• What does the area under each peak in GC represent?

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

  Analysis in forensics and environmental studies
• What factors can change retention times in GC?

  Column temperature, length, and flow rate
• What happens if the temperature or flow rate is higher in GC?

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

  It does not react with components being separated