A-level Chromatography

What is the mobile phase in paper chromatography?

solvent

What is the stationary phase in paper chromatography?

Absorbent paper

If a stronger affinity for mobile phase ...

moves quickly

If a stronger affinity for the stationary phase ...

moves slowly

What is the stationary phase in column chromatography?

SiO2/Al2O3 powder

What is the mobile phase in column chromatography?

Solvent

What is the stationary phase in TLC chromatography?

SiO2/Al2O3 powder on glass/plastic plate

What is the mobile phase in TLC chromatography?

Solvent

What is the stationary phase in Gas chromatography?

SiO2/Al2O3 powder

What is the mobile phase in Gas chromatography?

Inert gas

What is the solvent used for the mobile phase called?

Eluent

Give an example of a non-polar solvent

Alkanes

Give examples of polar solvents

Water, alcohols

What are the advantages of TLC chromatography?

Smaller amounts of mixtures can be separated

Plates are more robust than paper

What can TLC chromatography be used for?

Colourless samples

Results can be viewed using UV light

What is a benefit of using ninhydrin when analysing amino acid using TLC chromatography?

Don't need UV light to see samples

How is RF calculated?

distance moved by spot/distance moved by solvent

What is an advantage of using Column chromatography?

Can use large amounts

What kinds of liquids would use Gas chromatography?

Volatile liquids

What is the retention time?

Time taken to travel through the tube

What is the process?

Long coiled tube packed with powder

Inert gas passed through tube

Sample analysed by mass spec

Why does separation occur in chromatography?

Different substances have different polarities and different relative affinities for the stationary and mobile phase

What factors affect the Rf value in TLC chromatography?

Temperature

solvent

What factors affect the retention time in column chromatography?

Length of column

temperature

Solvent

How does column chromatography work?

glass column is packed silica/alumina

mixture to be separated is added to the top of the column

solvent is added to top of column and continuously run through

Different substances leave the column at different times and can be collected in different flasks at the bottom

What is the key measurement in gas and column chromatography?

Retention time

What factors affect the retention time in gas chromatography?

Length of column

Temperature

Gas pressure

Give an example of an inert gas used for gas chromatography

Hydrogen