Mass Spectrometry (TOF)

Mass Spectrometry (TOF)

1. Ionisation Chamber

   • VAPOURISED atoms enter through sample inlet
   • Atoms are bombarded with a beam of electrons
   • Each atom loses and electron from its outer energy level to become a POSITIVE ION
     • They must be ions so that they can create a current on the ion detector
     • This allows them to be accelerated

2. Acceleration Area

   • All the ions are given the same energy by an electric field
   • The magnetic field is adjusted so that each isotope can be detected in turn
     • Changes the amount of deflection as the mass of each isotope is different

3. Drift Region

   • All the ions have the SAME KE
   • Their speed of travel is INVERSELY PROPORTIONAL to their mass
   • Ions are SEPARATED according to their mass
     • Heavier ions travel slower

4. Ion Detector

   • The ions hit the detector at different times depending on their mass
   • A CURRENT is created when they hit the detector
   • The HEAVIER that the ion is, the GREATER THE CURRENT

5. The mass spectra is within a vacuum so that none of the ions collide with air molecules

6. Spectra

   • The abundance of each ion is recorded
   • Relative Atomic Mass
     • The average mass of an atom of on type of element