CHROMATOGRAPHY

• WHAT IS CHROMATOGRAPHY?

  used to separate a mixture when dissolved in a solvent and the resulting solution (mobile phase) moves over a solid (stationary phase)
• MOBILE PHASE?

  • carries soluble components
  • the more soluble a component is the faster it moves
• NAME FOR SOLVENT?

  eluent
• STATIONARY PHASE?

  • hold back components that are attracted to it
  • higher affinity of component means it moves slower
• TYPES OF CHROMATOGRAPHY?

  • paper
  • thin-layer (TLC)
  • column
  • gas-liquid (GC)
  • GCMS
• THIN-LAYER CHROMATOGRAPHY?

  • development of paper chromatography
  • filter paper replaced by glass/ metal/ plastic sheet
  • coated with thin layer of silica gel (silicon dioxide)/ alumina (aluminium oxide)
  • to produce stationary phase ("plates)
  • colourless spots located using UV light or locating agent
  • calculate Rf
• BENEFITS OF TLC OVER PAPER?

  + runs faster

  + smaller amounts required

  + spots spread out less

  + plates more robust than paper
• COLUMN CHROMATOGRAPHY?

  • uses powder (silica or aluminium oxide) or resin
  • packed into column
  • to produce stationary phase
  • eluent added to top of column so runs down
  • to produce mobile phase
  • components travel down at different rates so are separated in collecting flask
  • can separate mixture of AAs
• BENEFITS OF COLUMN CHROMATOGRAPHY?

  + large amounts can be separated/ collected
• GAS-LIQUID CHROMATOGRAPHY?

  • uses powder coated with oil in capillary tubes and placed in an oven (vary temperature)
  • to produce stationary phase
  • unreactive gas (nitrogen/ helium) used as mobile phase
  • after injection sample is carried along by gas so the mixture separates
  • some moved along by gas, some retained by oil each to a different degree
  • different retention times
  • detector measures thermal conductivity of gas
  • components fed into NMR/ mass/ infrared spectrometer
  • match retention time with known substance under same conditions
• BENEFITS OF GC?

  + extremely sensitive

  + used in blood/ urine tests of athletes
• GCMS?

  • gas chromatography-mass spectrometry
  • MS is a detector for GC system
  • GC measures retention time
  • MS identifies compound by fragmentation pattern or accurate mass