mass spectrometry

ionisation
1. the samples hit with a high energy stream of electrons from the electron gun.
  1. these electrons 'knock off' the electrons in the outer shell.
    1. this causes the atom of molecule to form a postivly charged ion
2. IF the electron from the electron gun has a high enough energy ANOTHER electron will be removed
  1. this causes a doubly charged ion
    1. eg;
heres the basic principle;
ACCELERATIOn
1. ions are now accelerated by an electric field caused by the positive charged plates.
  1. the slits in the plates narrow the beam
    1. the ions are accelerated towards the magnetic field.
      1. the rate at which they're accelerated is proportional the the m/z ratio.
deflection
1. accelerated ions are deflected by an electromagnetic field
  1. for each ion the degree of deflection depends on the m/z ratio
    1. DEFLECTIONS GREATER IF
      1. the mass of the ions smaller
      2. the charge of the ions greater
      3. the strength of the field greater
    2. DEFLECTIONS LESS IF;
      1. the mass of the ions larger
      2. charged of +ve ions lower
      3. the strength of magnetic fields less
detection
1. as an ion reaches a detector it produce a tiny current.
  1. the number of electrons realised and the current produced is proportional to the number of ions striking the detector
    1. the detectors linked to an amplifier
      1. then to a recorder which converts the current into a peak which is shown on mass spectrum.
interpreting the mass spectra;
1. mass spectra are graphs which give info about each ion produced in the sample
  1. it shows m/z ratio of each ion
  2. shows abundance of each ion
  3. infos used to work out relative atomic mass

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mass spectrometry

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