Chromatography

• What is chromatography used for?

  Separate and identify components
• All forms of chromatography involve the distribution of components between a stationary and a moving phase.
• A phase in chromatography refers to a state such as solid, liquid, or gas
• What is the moving phase in chromatography called?

  Mobile phase
• The stationary phase in chromatography moves along with the mobile phase.

  False
• What two factors determine the separation of components in chromatography?

  Solubility and retention
• If the stationary phase is a solid, separation depends on the balance between solubility in the moving phase and retention by adsorption
• How does stronger retention to the solid stationary phase affect the movement of a component?

  Slows it down
• When the stationary phase is a liquid, separation occurs through solubility.
• The rate of movement of a component is recorded as either an Rf value or a retention time
• What is the purpose of Thin Layer Chromatography (TLC)?

  Checking purity and identifying components
• The stationary phase in TLC is typically a solid such as SiO2 or Al2O3.
• The mobile phase in TLC is a liquid solvent
• Steps in performing a TLC experiment

  1️⃣ Dissolve the sample in a solvent

  2️⃣ Draw a pencil line on the TLC plate

  3️⃣ Place a small spot of the sample on the line

  4️⃣ Place the plate in a beaker with solvent

  5️⃣ Seal the beaker with a lid

  6️⃣ Allow the solvent to rise up the plate

  7️⃣ Mark the solvent front
• What is the purpose of locating agents in TLC?

  Make compounds visible
• The Rf value in TLC represents the distance moved by a spot as a fraction of the distance moved by the solvent.
• The formula for Rf value is: distance moved by spot / distance moved by solvent
• Calculate the Rf value for compound C if it moved 28mm and the solvent moved 62mm.

  0.45
• Similar compounds in TLC will always have exactly the same Rf values.

  False
• What is the main use of Column Chromatography (CC)?

  Separate and collect large amounts
• The stationary phase in CC is a solid such as SiO2 or Al2O3
• What is the retention time in Column Chromatography?

  Time to reach detector
• Gas Chromatography (GC) is best suited for separating volatile compounds.
• What type of carrier gas is used in Gas Chromatography?

  Inert carrier gas
• Retention time in Gas Chromatography is the time taken for a component to pass from the column inlet to the detector
• What does the area under each peak in a Gas Chromatogram represent?

  Amount of a component
• Many compounds in GC can have the same retention time.
• Combining Gas Chromatography with Mass Spectrometry creates a tool called GCMS
• What is the role of mass spectrometry in GCMS?

  Analyze separated components