TOPIC 7: Modern analytical techniques

Question 1

What are the steps for mass spectrometry?

Answer 1

1. Place your element in the sample chamber
2. The atom will go through ionization and will lose an electron, making it a positive ion. This happens because it is bombarded with a high energy beam which knocks off an electron.
3. The atom is now attracted to a negatively charged plate, which leads the ions to accelerate towards the plate
4. All of the ions have the same KE.
5. Once passing the negatively charged plate, they stop accelerating and start ion drift. This is where the ions drift to the end of the machine.
6. The lighter ions drift faster and reach the end faster.
7. An electromagnet changes the direction of the drift of the electrons to a side.
8. The one with the smallest weight will curve the most and touch the side, where it gets detected.
9. Once ions reach the end, ion detection takes place which leads to them gaining an electron which creates a current.

Question 2

What conditions must be met for a mass spectrometer to work?

Answer 2

The mass spectrometer must be in a vacuum to avoid air molecules from colliding with the wanted isotopes.

Question 3

How can the results of a mass spectrometer be interpreted?

Answer 3

• Points reached in the machine explain the mass of the atom.
• Current produced is used to find the abundance of an isotope.

Question 4

What does M/Z stand for?

Answer 4

Mass : Charge ratio.

Question 5

What is fragmentation?

Answer 5

Fragmentation occurs during acceleration and it is the breaking of the molecules into fragments due to the breaking of covalent bonds in the molecular ions. A fragment ion can occur and be found in the test that we carry out and appear in the mass spectrometer.

Molecular ion –> Fragment ion + Racidal / Natural species

Question 6

Describe infrared spectrometry?

Answer 6

The infrared radiation is not strong enough to break down the bonds but allows them to vibrate instead.

Question 7

How does infrared spectrometry work?

Answer 7

The infrared spectrum works by having a machine detect all these vibrations in different directions and then getting a value out of them to compare that value to known values of molecules. You can find out what is in the molecule and its functional group, homologous series etc.

Question 8

What is the fingerprint region?

Answer 8

It is where you no longer count peaks and it is just below 1300.