Unit Three, Chapter Thirty Seven - Chromatography Flashcards
What is chromatography?
A technique used to separate the components present within a mixture
How does chromatography work?
Separates substances by making use of differences in their polarity or molecular size
Describe the stages of TLC
(1) A small sample of the mixture being tested is spotted onto the base line of the chromatogram
(2) A solvent dissolves the compounds in the spot and carries the compounds up the chromatogram
(3) How far the compounds are carried depends on solubility in the chosen solvent and how well they adhere to the plate
(4) A developing agent or UV light is often required to visualise the spots
What is the main piece of equipment required for TLC?
Fine film of silica or aluminium oxide spread over glass
How to calculate Rf values
Rf = distance travelled by the sample/distance travelled by the solvent
What is TLC used for?
To assess the purity of substances by determining what substances are present
The presence of only one spot indicates…
That the substance is pure
The presence of more than one spot indicates…
That impurities are present
