Mass Spectrometry

Mass Spectrometry

1. Uses

   • Relative atomic mass
   • Relative molecular mass
   • relative isotopic abundance
   • Molecular structure

2. Step 1- Vaporisation

   • The sample is vaporised by an electrical heater

3. Step 2- Ionisation

   • The gas particles are bombarded with high energy electrons to ionise them by knocking off electrons, leaving positive ions.

4. Step 3- Acceleration

   • The positive ions are accelerated by an electric field

5. Step 4- Deflection

   • The positive ions' paths are altered with a magnetic field. Lighter ions have less momentum so are deflected more than heavier ions. For a given magnetic field, only ions with a particular mass/charge ratio make it to the detector.

6. Step 5- Detection

   • The magnetic field strength is slowly increased. As this happens, different ions can reach the detector. As they hit the detector they release a current.The bigger the current the more of that isotope is present in the sample. A mass spectrum is produced.

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