Mass Spectrometer

Mass spectrometry can be used to identify compounds because different compounds all produce a unique pattern of relative abundances of isotopes. It was used by the Viking space probe, which landed on Mars to identify elements on the Martian surface. A mass spectrometer can also be used to calculate the relative atomic/isotopic mass of atoms.

Main stages of a mass spectrometer:

Vaporised

The sample is vaporised by using a high temperature. A low pressure is also necessary to create a vacuum, which ensures only the sample you want to test is present.

Ionisation

The sample is bombarded by high energy electrons from an electron gun to produce positive ions.

Acceleration

An electric field produces negatively charged plates, which accelerates the ions.

Deflection

An electromagnet creates a magnetic field, which defects the ions, with the degree of deflection dependent on the mass/charge ratio (the lower the mass or the greater the charge the greater the degree of deflection).

Detection

Arriving ions produce an electric current that produces a mass spectrum, the greater the area under the peak, the greater the abundance.

Mass Spectrum:

Example: The Relative isotopic mass and percentage abundance of Magnesium: