Mass Spectrometer

Chemical Ideas 6.5

Mass spectrometry is used to measure the atomic or molecular mass of different particles, as well as their relative abundance. It takes place in a (time of flight) mass spectrometer.

The mass spectrometer is a vacuum chamber, allowing the ions to travel from one end to the other without any hindrance by collisions with air molecules.

There are five key parts to the mass spectrometer: the sample inlet, ionisation area, acceleration area, drift region and the ion detector.

Sample Inlet, where:

• gases or liquids are injected into the ionisation area
• solids are heated to vaporise sample

Ionisation Area, where:

• heated filament produces high-energy electrons
• high-energy electrons bombard atoms or molecules in the sample (electron impact)
• sample is ionised, forming CATIONS
• X (g) + e- --> X+ (g) + 2e-
• fragments are formed.

Acceleration Area, where:

• …