3.16 Chromatography

• what are the principles of chromatography?

  - technique that enables the separation of mixture

  - make use of the principle that components in a mixture when dissolved in a fluid (mobile phase), will flow through another material (stationary phase) at varying rates

  - rate of separation depends upon how the components in the mixture interact with the stationary phase (their retention) and how soluble they are in the mobile phase
• what is the stationary phase and mobile phase in Thin-layer (TLC)?

  stationary - solid silica on a plastic or gas phase

  mobile - liquid solvent, e.g. water or organic
• what is the stationary phase and mobile phase in column chromatography (CC)?

  stationary - solid silica

  mobile - liquid solvent, e.g. water or organic
• what is the stationary phase and mobile phase in gas chromatography (GC)?

  stationary - microscopic film on a solid support

  mobile - inert carrier gas, e.g. nitrogen
• how do you calculate retention factor?

  Rf = distance travelled by component / distance travelled by solvent
• in column chromatography, what takes the longest time to flow through the column?

  the component with the greatest attraction / affinity to the stationary phase
• what does a high Rf value show?

  they are more soluble in the mobile phase and get carried forwards with the solvent