33 - Chromatography Flashcards
Give three types of chromatography.
Thin-layer
Column
Gas
Describe thin-layer chromatography.
A plate is coated with a solid, and a solvent moves up the plate.
Describe column chromatography.
A column is packed with a solid and a solvent moves down the column.
Describe gas chromatography.
A column is packed with a solid or with a solid coated by a liquid, and a gas is passed through the column under pressure at high temperature.
What is separation in chromatography controlled by?
Solubility in mobile phase, and retention by stationary phase.
How are different substances identified in chromatography? (2)
Retention times
Rf values
How is the retardation factor calculated in thin-layer chromatography?
Distance moved by sample/distance moved by solvent (should be 0<x<1)
What range should an RF value fall in?
0<Rf<1
How can the results of thin-layer chromatography be seen?
UV light or ninhydrin spray
Why is it essential that the solvent is below the pencil line?
If higher than the pencil line, the mixture dissolves.
Why is the Rf value of 1,2-dinitrobenzene increased when in a solvent of hexane compared to cyclohexane?
Solvent more polar
Stronger affinity to solvent
Suggest a suitable reagent for the hydrolysis of a protein?
Concentrated HCl
