The Mass Spectrometer

Question 1

Stages of the mass spectrometer

Answer 1

1) Vaporisation.2) Ionisation.3) Acceleration.4) Separation in a magnetic field.5) Detection.

Question 2

Stage 1: Vaporisation

Answer 2

The liquid sample is injected into the instrument.There is a vacuum inside the chamber so the liquid turns into a gas - it becomes vaporised.

Question 3

Stage 2: Ionisation

Answer 3

The vaporised sample passes into the ionisation chamber.The particles in the sample are bombarded with a stream of electrons.The collisions will knock one or more electrons out of the sample particles to make positive ions.

Question 4

Stage 3: Acceleration

Answer 4

Negatively charged plates in the accelerator attract the positively charged ions out of the ionisation chamber and into the accelerator.As the ions pass through the plates they accelerate and an ion beam passes into the separator.

Question 5

Stage 4: Separation in a magnetic field

Answer 5

A single beam of mixed ions passes into the electromagnet.Different ions are deflected by the magnetic field by different amounts.The amount of deflection depends on the mass of the ion (lighter ions are deflected more than heavier ions).

Question 6

Stage 5: Detection

Answer 6

By changing the strengths of the magnetic field, ions of different masses are focused on the detector.The signal is amplified and can be viewed on a computer screen.The signal is sent to a recorder which traces out a mass spectrum.

Question 7

Uses of the mass spectrometer

Answer 7

Identify the presence of isotopes.Measure the relative abundances of isotopes.Measure relative atomic masses and relative molecular masses.Identify unknown compounds.