Chromatography
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What is the stationary phase?
molecules cannot move through
What is the mobile phase?
molecules can move through
Describe TLC
• piece of glass coated in silica gel (SP) • sample dropped onto line on TLC plate • TLC plate put into solvent (MP) • when dry observed under UV light.
What is the MP in TLC
the solvent
What is the SP in TLC
silica gel
describe solubility and affinity for TLC
the further up the the sample has travelled the more soluble it is in MP and has low affinity in the SP
adv of TLC
faster works on small samples
disadv of TLC
cannot be use to separate large amounts
How to calculate Rf value
distance moved by component/distance moved by solvent
Describe column chromatography
• column packed with silica (SP) • pour mixture in column. • solvent poured on top (MP) • diff components travel down at diff rates - one reaches the bottom and be collected off (next can be collected off sometime later)
adv of CC
can be used to separate large quantities
what does higher charges mean in terms of polarity of a molecule
molecule is more polar
What is the MP in CC
solvent
What is the SP in CC
silica
what is GLC used for
to separate mixture of volatile components
describe GLC
• carrier gas (helium/nitrogen) flows through capillary column (MP) • Column lined with gel (SP) • sample injected through column • carrier gas transports components along until detector reached where a current is produced • retention time measured
What is the MP in GCL
carrier gas
What is the SP in GCL
coating of gel
what is retention time
how long it takes for the component to move from the point of injection to the detector.
limitations of GCL
Chromatogram produces many peaks