Chromatography

Question 1

Define Chromatography

Answer 1

It is a separation technique in which a mobile phase carrying a mixture moves in contact with a selectively adsorbent stationary phase.

Question 2

What is the principle of chromatography

Answer 2

The principle on which all chromatography separation techniques are based is that separation of a mixture of components occurs as a result of selective adsorbance of the components of the mixture on a stationary phase while carried by a mobile phase.

Question 3

Describe gas chromatography.

Answer 3

gas chromatography uses a gas as the mobile phase. The stationary phase is a non-volatile liquid spread on solid inert particles that are packed into a long coiled tube called a column.

Question 4

What is a carrier gas, give an example.

Answer 4

A gas that carries the vaporised sample in gas chromatography through the column, eg nitrogen, helium, argon.

Question 5

What is the principle of gas chromatography?

Answer 5

The principle of gas chromatography is that a gaseous mobile phase is in contact with a stationary phase (non-volatile liquid) and separation of the mixture occurs as a result of selective adsorbance of the components of the mixture on the stationary phase.

Question 6

What is gas chromatography commonly used for?

Answer 6

To measure the level of alcohol in blood or urine samples or to carry out drug tests on athletes.

Question 7

What is GC-MS used for?

Answer 7

To detect gases from waste dumps and organic pollutants in water/ to monitor the performance of a particular pharmaceutical in the body.

Question 8

What does HPLC stand for?

Answer 8

High performance/Pressure liquid Chromatography

Question 9

Describe HPLC

Answer 9

The substance being analysed is added to a liquid solvent (mobile phase) which is passed over very fine silica particles (stationary phase)

Question 10

What is the principle of HPLC

Answer 10

That a liquid mobile phase is in contact with a stationary phase (fine particles of a solid) and separation of the mixture occurs as a result of selective adsorbance of the components of the mixture on the stationary phase.

Question 11

Is HPLC performed at higher or lower temperature than GC and why

Answer 11

Lower, it can be used to analyse compounds that would decompose at the high temperatures of GC.

Question 12

Name two analytical techniques

Answer 12

infra-red spectrometry and ultraviolet spectrometry

Question 13

What are IR cameras used for ?

Answer 13

To find people buried in collapsed buildings

Question 14

Whats is the principle of infra-red spectrometry?

Answer 14

that organic compounds absorb infra-red radiation of certain frequencies. The combinations of frequencies that are absorbed depend on the bonding within the molecule and are unique to the particular molecule.

Question 15

Summarise the infra-red process

Answer 15

IR radiation is passed through a sample being analysed, IR radiation of certain fixed frequencies is absorbed, an absorption spectrum is obtained which can be used to identify the compound.

Question 16

What is UV spectrometry used for?

Answer 16

to detect the presence of certain functional groups in molecules. Or in quantitative analysis to measure the concentration of certain organic compounds in solution eg plant pigments and drugs. In biochemistry, it can be used to measure the amount of drug metabolite reaching a certain part of the body.

Question 17

What is the principle of UV spectrometry

Answer 17

that absorbance is directly proportional to the concentration of a substance.

Question 18

What is UV spectrometry used for?

Answer 18

In conjunction with HPLC, it can detect the presence of compounds such as transition metals, drug metabolites and plant pigments and to measure their concentrations.