Mass Spectrometry

• • The sample is vaporised, turning it into a gas.
  • When an organic compound id placed in the mass spectrometer, an electron beam is fired at the gaseous molecules, knocking out an electron to form a positive molecular ion.
  • The detector detects the mass-to-charge ratio (m/z) of the molecular ion which gives the molecular mass of the compound which is shown on a mass spectrum.
• • The molecular ion peak is the clear peak at the highest m/z value on the mass spectrum.
• • In the mass spectrometer, some molecular ions break down into smaller pieces known as fragments in a process called fragmentation.
  • The other peaks in the mass spectrum are cased by fragmentation.
• • The simplest fragmentation breaks a molecular ion into two species - a positively charged fragmentation and a radical.
  • The positive ions formed will be detected by the detector of the mass spectrometer, but any uncharged radicals will not be detected.
  • The mass spectrum of each compound is unique as molecules will all fragment in slightly different ways depending on the structure.