Mass spectrometry

Question 1

What are the four steps in a mass spectrometer?

Answer 1

Ionisation, acceleration, ion drift and detection

Question 2

Describe what happens in the first step of a mass spectrometer

Answer 2

1. A sample is dissolved in a volatile solution
2. The vaporised solvent is forced through a hollow needle connected to the positive terminal of a high voltage power supply
3. This produces positive droplets as they have lost electrons
4. The solvent then evaporates from the droplets causing them to reduce in size until small positive ions are left

Question 3

Describe what happens in the second step of a mass spectrometer

Answer 3

The positive ions are attracted to a negatively charged plate causing ions to accelerate towards the plate so all the ions have equal kinetic energy therefore larger and heavier particles will have a lower speed and vice versa

Question 4

Describe what happens in the third step of a mass spectrometer

Answer 4

The ions then pass through a hole in the negatively charged plate into the flight tube forming a beam which travels along it

Question 5

Describe what happens in the fourth step of a mass spectrometer

Answer 5

1. The ions are now at the detector where the flight time is recorded as the positive ions pick up an electron causing a current to flow
2. The current then causes a signal to be passed to the computer which generates the mass spectrum