Chromatography

    Cards (25)

    • What are the 2 phases in chromatography?
      Stationary & mobile phase.
    • What is a stationary phase?
      A stationary phase is a solid or liquid material that is used in chromatography to separate and analyze different components of a mixture.
    • What is a mobile phase?
      The liquid or gas that carries the sample through a chromatography system.
    • What will the mobile phase do?
      Carry the sample through the stationary phase.
    • List the common types of chromatographic techniques
      • Column chromatography
      • Thin layer chromatography (TLC)
      • Gel filtration
      • Ion exchange
    • What does normal phase column chromatography do?
      Separates compounds based on their polarity.
    • Explain the process of normal phase column chromatography
      • Column is tightly packed with stationary phase
      • Silica interacts with drug (more strong with polar compounds)
      • Solvent is carried over to a detector which measures UV rays and displays peaks based on the components in the solvent
      • The peaks can be studied later to determine their structure
    • What is the most common stationary phase in chromatography?
      Silica gel
    • Will polar or non-polar compounds interact more strongly with the stationary phase?

      Polar
    • What does elution mean?
      Movement of compounds through the column.
    • List the difference in elution & binding to stationary phase between non-polar & polar compounds
      Polar - bind strongly & elute slowly
      Non-polar - bind weakly & elute quickly
    • Give an example of a high and low polar solvent
      High - water
      Low - n-hexane
    • How does elution link to retention time?
      Fast elution = short retention time (weaker interactions with stationary phase)
      Slow elution = long retention time (stronger interactions with stationary phase)
    • Column chromatography is often used as a purification tool - what does this mean?
      It isolates the desired compounds in their pure form from the rest of the mixture (into fractions).
    • How does thin layer chromatography work?
      • Thin layer of stationary phase (silica gel) spread on a flat surface
      • Small amount of sample applied at bottom of TLC plate
      • Place placed in shallow container with a solvent (mobile phase) at the bottom - this moves up the plate by capillary action
      • As solvent rises, compounds will move at different rates depending on their polarity
      • More polar = interact more strongly with stationary phase = move slower
      • Less polar = interact more weakly with stationary phase = move faster
      • After solvent reached top, plate is removed & compounds visualised using UV light
    • What does retention factor measure?
      How far the substance has travelled.
    • What can TLC be used for?
      • Assessing purity of a compounds
      • Identify compounds based on their RF values
    • What is gel filtration chromatography used for?
      • To purify large molecules
      • Remove salts from large molecules e.g. proteins
      • Determine molecular weight of unknown proteins
    • How does gel filtration chromatography work?

      • Column packed with porous beads (stationary phase)
      • Sample loaded onto column & a buffer (mobile phase) is used
      • Large molecules can't enter pores of beads & pass through column faster (elute faster)
      • Smaller molecules enter pores & take longer to pass through (elute slower)
      • Components get separated due to elution times
    • Give examples of the stationary phases used in gel filtration chromatography
      Dextran & agarose
    • How is the stationary phase in ion exchange chromatography different to other methods of chromatography?
      They stationary phase must have a charge (must have ionisable groups on it).
    • How does ion exchange chromatography work?
      It has the same principle as column chromatography but stationary phase will be charged & attract the opposite charge.
      Molecules will weak ionic interactions will elute first.
    • How can we elute the solvent in ion exchange chromatography?
      By changing the pH or ionic strength.
    • What will the charge be on anionic and cationic exchangers
      Anionic = +ve
      Cationic = -ve
    • When is ion exchange chromatography used?
      • To separate charges on amino acids
      • Water purification