RP06 - Chromatography

• What is chromatography?

  A family of separation techniques
• What principle does chromatography depend on?

  Separation of a mixture in a solvent
• What is the mobile phase in chromatography?

  It carries the soluble components
• What relationship makes a sample move faster in chromatography?

  More soluble components move faster
• What does the stationary phase do in chromatography?

  Holds back components attracted to it
• What relationship makes a sample move slower in chromatography?

  More affinity for the stationary phase
• What kind of bonding often slows down a sample in chromatography?

  Hydrogen bonding
• How are substances separated by chromatography?

  Different affinities for mobile and stationary phases
• Why do different substances show different Rf values?

  They have different polarities and bonding
• What does TLC stand for?

  Thin Layer Chromatography
• What is the stationary phase in TLC?

  Silica or alumina coated plate
• What are the advantages of TLC over paper chromatography?

  Runs faster and uses smaller amounts
• How can you observe colourless spots in chromatography?

  Shine UV light or use a developing agent
• How do you calculate the Rf value?

  Rf = distance moved by spot / distance moved by solvent
• What does Rf value stand for?

  Retention factor
• How can you confirm the identity of a substance from its Rf value?

  Compare Rf value to accepted values
• What is column chromatography?

  Column packed with silica or resin
• What is the stationary phase in column chromatography?

  Silica, alumina, or resin packed in a column
• What is the mobile phase in column chromatography also known as?

  Eluent
• What are the advantages of column chromatography?

  More than one eluent can be used
• What is the stationary phase in gas-liquid chromatography?

  Powder coated with oil in a capillary tube
• What is the mobile phase in gas-liquid chromatography?

  Carrier gas, e.g., N2 or He
• What do you measure in gas-liquid chromatography?

  Retention time of components
• What are the advantages of GLC?

  Very sensitive to minute traces
• What are GLC's uses?

  Testing blood and urine for drugs
• How can you use GC or GCMS to identify substances?

  Match retention time to known substances
• How does GCMS work?

  Run GC, record retention time, then use MS
• Which has a shorter retention time, alcohol or aldehyde?

  Aldehyde has the shortest retention time