33 Chromatography

Question 1

Rf value

Answer 1

Distance travelled by solute / distance travelled by solvent

Question 2

TLC advantage over paper chromatography

Answer 2

Runs faster
Small amounts of mixture can be separated
Spots spread out less
Plates are more robust

Question 3

Column chromatography

Answer 3

Uses a powder ( scilia and aluminium oxide )
Stationary phase
Packed into a narrow tube
Runs down the column ( moving an different rates and can be collected separately )
More than one can be used / large amount can be separated / better separation
(column chromatography (CC) – a column is packed with a solid and a solvent moves down the column)

Question 4

Gas chromatography

Answer 4

Stationary phase = powder coated in oil (packed in a long capillary tube)
Mobile phase = unreactive gas (nitrogen / helium)

Sample is carried along by the gas and mixture separated the compounds because they have different retention times
Different detectors can be used
Automated and computer controlled / can separated mixture traces of substance in food stuff
Identification of a component is done by matching the retention time with one of the known substances
(gas chromatography (GC) – 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)

Question 5

Gas chromatography-mass spectrometry

Answer 5

Two techniques at once ( mass spectrometer and gas chromatography)

Rention time noted

Automatically into mass spectrometer which enables the compound to be identified either by its fragmentation or measuring its accurate mass

Question 6

High-pressure liquid chromatography

Answer 6

Forced through a column containing stationary phase
Many materials can be worked out including chiral
Can be detected by UV light

Question 7

Chromatography basic

Answer 7

The sample is dissolved in a solvent ( solution is now the mobile phase ) and passed over a solid such as filter paper or silica power

Substance in the sample will have a varying affinity to the stationary phase, with the one with the strongest attraction taking the longest to move

Question 8

TLC

Answer 8

thin-layer chromatography (TLC) – a plate is coated with a solid and a solvent moves up the plate

Question 9

separation

Answer 9

Separation depends on the balance between solubility in the moving phase and retention by the stationary phase.

Question 10

RF

Answer 10

Retention times and Rf values are used to identify different substances.