3.3.16 - Chromatography

Question 1

Chromatography

Answer 1

An analytical technique used to separate and identify component molecule of a mixture

Question 2

Mobile phase

Answer 2

Substance that allows molecules to move over or through the stationary phase

Question 3

Stationary phase

Answer 3

Substance that has affinity to molecule in the mixture being analysed

Question 4

The greater the affinity of a molecule to the stationary phase…

Answer 4

The shorter the distance it moves with the mobile phase

Question 5

Rf value

Answer 5

Value that is unique to each different component molecule in the mixture being analysed

Question 6

Thin-layer chromatography

Answer 6

A metal plate is coated with a thin layer of silica and solvent moves up the plate. The plate is then dried in a fume cupboard to reduce toxic fumes

Question 7

Viewing of chemical traces in thin-layer chromatography

Answer 7

Using a UV lamp and the distances travelled can be measured. Or, a developing agent such as iodine can be added to allow traces to be visible to the naked eye

Question 8

Column chromatography

Answer 8

A vertical column is packed with a solid, powdered substance which acts as the stationary phase. A solvent containing the mixture being analysed is then added and moves down the column as the mobile phase

Question 9

Varying affinities of molecules present in column chromatography means…

Answer 9

They drain out of the column at different times. The time taken to drain out of the column is measured as the retention time

Question 10

Gas chromatography

Answer 10

A thin tube is packed with a solid, powdered substance which acts as the stationary phase. A high pressure gas is passed through this tube as the mobile phase.

Question 11

Gas chromatography separates mixtures of…

Answer 11

Volatile liquids which are fed into the gas chromatography machine as vapours

Question 12

Gas chromatography analysis machine records…

Answer 12

A retention time for each component molecule in the mixture

Question 13

GC-MS

Answer 13

Combination of analytical techniques, gas chromatography and mass spectrometry, allowing for a more advanced level of molecule analysis

Question 14

Molecules present in GC-MS are first…

Answer 14

Separated using the gas chromatography technique

Question 15

Each molecule present in GC-MS is then…

Answer 15

Fed directly into a mass spectrometer so it can be accurately identified

Question 16

Speed and accuracy of GC-MS

Answer 16

Much faster analytical process that produces more accurate results for molecule analysis and identification