C4.2.4 - Instrumental methods of analysis

Question 1

What is an instrumental method of analysis?

Answer 1

A technique for analysing a substance that depends upon a machine

Question 2

What are advantages of using instrumental methods?

Answer 2

Sensitivity - They can analyse small amounts of substances
Accuracy - They are very accurate and can be calibrated using internationally accepted standards
Speed - They can carry out analyses quickly and can run all the time

Question 3

What is a gas chromatogram?

Answer 3

A chart that represents the difference substances in a mixture

Question 4

How do you interpret gas chromatograms?

Answer 4

• each peak represents a substance present in the mixture
• the areas under each peak show the relative amount of each substance in the mixture
• the retention time show the the time take for a substance to travel through the chromatography column

Question 5

What is a mass spectrometer?

Answer 5

A machine that can measure masses of atoms and molecules

Question 6

Where is mass spectrometer used?

Answer 6

In many fields of science, such as in environmental science, for which scientist use it to detect toxic substances

Question 7

What are molecular ions?

Answer 7

Positive ions formed in a mass spectrometer when an electron is removed from an atom or molecule

Question 8

How do you interpret mass spectra?

Answer 8

• Each peak represents a fragment of the molecule
• The peak on the far right represents the molecular ion
• The mass to charge ratio of the molecular ion peak is equal to the relative formula mass of the molecule

Question 9

What is retention time?

Answer 9

The time taken for a substance to travel through a gas chromatography column