A machine for performing mass spectrometry on chemical samples

A mass spectrometer consists of sample chamber, in which the sample is heated by untill it is gaseous, and then bombarded with electrons from an electron gun. The gun "knocks" electrons off the sample, turning the molecules into charged ions. The ions are then accelerated by an electric field and deflected by a magnetic field. Heavier ions are deflected less than lighter ions, and so the exact mass of the ions is determined by where they hit the detector. This produces a mass spectrum, which shows the mass and relative proportion of the different ions that were in the sample enabling the exact contents of the sample to be determined

A more recent innovation is the use of "time of flight" mass spectrometry, which measures the time of flight taken by each of the ions. Since heavier ions accelerate less, they will take longer and the mass spectrum can be determined by the time taken by each ion.

A major problem with mass spectrometry is that it can fragment molecules, breaking large molecules into smaller ones. Although this can be useful, most of the time it confuses the mass spectrum. The major advantage of time of flight spectrometry is that it produces less fragmentation.

More advanced spectrometers can perform a number of aditional functions, such as protein mass spectrometers, which actually use two spectrometers, to fragment the protein and analyse the amino acid fragments or mass spectrometers linked into a gas chromagraph, which separates samples prior to analysis