Mass spectrometry

Question 1

What are the 4 stages in Mass Spectrometry

Answer 1

Ionisation
Acceleration
Ion drift
Detection

Question 2

Explain what happens in the Ionisation stage (2 types)

Answer 2

Electrospray ionisation - sample is dissolved in a solvent and pushed through nozzle at high pressure. High voltage is applied, making each particle gain a H+ ion

Electron impact - sample is vaporised and electron gun fires high energy electrons at it. This knocks one electron off so it becomes +1 ions

Question 3

Explain what happens in the Acceleration stage

Answer 3

Positive ions are accelerated by an electric field. The electric field gives the same kinetic energy to all ions. Lighter ions have a greater acceleration

Question 4

Explain what happens in the Ion Drift stage

Answer 4

Ions enter region with no electric field. Drift through at the same speed as they least the electric field so lighter ions will drift at higher speeds than heavier ones

Question 5

Explain what happens in the Detection stage?

Answer 5

Lighter ions will hit the detector first creating a current which records how long it took to travel through spectrometer which will then be used to calculate mass/charge values for a mass spectrum

Question 6

What does TOF mass spectrometry detect?

Answer 6

The mass and relative abundances of isotopes

Question 7

How do you work out kinetic energy?

Answer 7

Half the mass times the velocity squared

Question 8

What is Hunds rule?

Answer 8

Electrons occupy empty orbitals before pairing to minimise repulsion