6.6 - Chromatography Flashcards
1
Q
What is chromatography used for?
A
to separate individual components from a mixture of substances
e.g analysis of drugs, plastics, flavourings, air samples
2
Q
What is the stationary phase?
A
doesn’t move (usually solid/liquid supported on solid)
3
Q
What is the mobile phase?
A
moves (usually liquid/gas)
4
Q
How to carry out TLC
A
- draw baseline with pencil on TLC plate
- spot small amount of solution on line with capillary tube
- pour solvent in beaker to depth below base line and add TLC plate, covering with watch glass on top
- leave solvent to rise until 1cm from top
- remove plate and mark solvent front with pencil
- allow plate to dry, then draw circles around visible spots
- calculate retention factor = distance moved by component/solvent
5
Q
Benefits of TLC
A
- quick
- inexpensive
- indicates no. components in mixture
6
Q
How is separation achieved in TLC?
A
different components have different affinities for adsorbent and bind w/ different strength to surface
7
Q
Describe how gas chromatography works
A
- small amount of mixture injected into gas chromatograph and carried by mobile phase through capillary column
- it slows down as interacts with liquid stationary phase
- more soluble in stationary phase = moves more slowly through tube so larger retention time
- each component produces a peak of gas chromatogram
- compare to known values to determine concs
8
Q
What is gas chromatography used for?
A
to separate/identify volatile organic compounds
