Chromatography Flashcards
1
Q
Define mobile state
A
Where molcules can move - always L or G
2
Q
Define stationary state
A
Molecules can’t move - solid or liquid on solid support
3
Q
What are the basic principles of chromatography?
A
- Mobile phase moves over/through stationary phase
- Distance each substance moves depends on solubility in mobile phase + retention by stationary phase
- Components more soluble in mobile phase moves further
- Diff. solubility + retention by stationary that seperate diff substances
4
Q
Outline how to carry out thin layer chromatography
A
- Stationary: thin layer silicon dioxide/aluminium oxide fixed to glass/metal plate
- Draw pencil line near bottom TLC + put drop on line
- Allow spot to dry
- Place in beaker w/ small vol solvent (mobile state), solvent must be below base to sample doesn’t dissolve
- Solvent moves up plate
- Remove + mark solvent front
- Place plate in fume cupboard
- Result: chromatogram
5
Q
Outline how to make colourless chemicals visible
A
- Add fluorescent dye to silica/alumina that glows under UV
- Expose chromatogram to iodine vapour - brown/purple
6
Q
How do you identify the substance?
A
Work out Rf value = distance travelled by spot/distance travelled by solvent
Compare to standard Rf values
7
Q
Outline how to carry out column chromatography + when to use it
A
- Purifying organic products
- Stationary: packing glass column w/ aluminium oxide coated w/ water
- Mixture added to top of column + drain into slurry, solvent run through column - mobile
- As mixture is washed through column, components seperate out depending on solubility in mobile + retention in stationary
8
Q
Outline how to carry out gas chromatography + when to use it
A
- Seperate volatile liquid (level of alcohol in blood/urine)
- Stationary: solid/solid coated w/ viscous liquid packed into longtube, coiled to save space
- Mobile: unreactive carrier gas - N
- Each component take diff amount of retention time - from injection to being recorded
