2.2.10 - Chromatography
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What is chromatography?
a technique used to separate components of a mixture to help identify the components
What are the two phases involved in chromatography?
stationary phase and mobile phase
what differs amungst components for the two phases?
their solubilities and affinities
When does the mixture separate?
as the mobile phase moves through the stationary phase
what affects the solubility of each component in each phase?
intermolecular forces
Why characterizes components for having higher affinity for the mobile phase?
when they have similar intermolecular forces as the solvent
in paper chromatography, what is the stationary phase?
the paper containing 10% water
in paper chromatography, what is the mobile phase?
the solvent which rises up the paper due to capillary action
How are components of a mixture separated in paper chromatography?
the solvent climbs the stationary phase and dissolves the components in the mixture to differing extents, carrying them at different rates and distances across the paper
What is the solvent front?
the line marked where the solvent stopped 1-2cm from the top of the paper
What is the final result once the components of the mixture can be distinguished?
chromatogram
What can each position of the components on a chromatogram be represented mathemtatically by?
Rf (retardation factor)
What is the formula for Rf?
Rf = distance moved by component/distance moved by solvent
In thin layer chromatography, what may be the stationary phase?
silica or alumina
What do the OH- groups in silica and alumina allow for?
hydrogen bonds to form with the components in a sample mixture