Mass Spectrometer

Mass Spectrometer

1. Vaporisation

   • Atoms must be vaporised to be to be turned into their gaseous state, if not in it's gaseous state already.
   • Ionisation
     • A beam of e- from an "e- gun" knocks out e-'s from atoms or molecules so they can become +ve ions
     • Acceleration
       • The +ve ions are attracted towards -vely charged plates and are accelerated to a high speed. The lighter the ions, the faster they go. Some ions pass through slits in the plates, forming the ions into a beam.
       • Deflection
         • Beam of ions moves into magnetic field at right angles to the direction of travel. Magnetic field deflects beam of ions into an arc of a circle. The deflection of an ion depends on the mass to charge (m/z). Heavier ions are deflected less than lighter ones. The deflection also depends on the magnetic field strength. The stronger the field, the greater the deflection.
         • Detection
           • The magnetic field is gradually increased, so the ions of increasing mass enter the detector one after another. Ions strike the detector, accept electrons, lose their charge, and create a current - proportional to the abundance of each ion.