Mass spectrometry

Mass spectrometry

1. 1) Ionisation

   • Electron Impact
     • Sample injected into the spectrometer and vaporised
       • High energy electrons from an electron gun are fired at the sample
         • The high energy electrons knock off an electron from each particle to form positive ions
   • Electrospray Ionisation
     • The sample is disolved in a polar solvent
       • and the injected through a fine hypodermic needle to give a fine mist
         • The tip of the needle is attached to the positive end of a high voltage supply
           • Particles gain a Proton (H+ ion) from the solvent to form postive ions

2. 2) Acceleration

   • An electric field is applied to accelerate the positive ion
     • This gives ions with the same charge the same kinetic energy
       • This means that the velocety at which an ion travels depends on its mass
         • Lighter ions travel faster
         • Heavier ions travel slower

3. 4) Detection

4. 3) Sepreration of ions

   • The positive ions travel through a mass spectrometer to reach the detector
     • The whole chamber is kept under vacuum conditions to prevent the positive ions colliding with molecules in the air