What is ionisation and why is it needed?
Ionisation is a physical process brought about in the source of the mass spectrometer. There are several possible ionisation methods and techniques in common use today – which technique is used depends on the compound being analysed and the type of information required. The theory section of this web site describes the most common techniques. Strictly speaking you don’t need to ionise compounds to analyse them by MS. You could make use of gravity broadening to separate molecules by their mass, but this would require instruments with flight tubes in the kilometre range! There are huge benefits to ionisation. The most obvious of which is that it allows instruments to be built in the laboratory scale – in fact ‘benchtop’ instruments are very common now. The smallest mass spectrometers actually fit inside a briefcase and just such instruments are used commonly by the military (explosives testing), customs and excise (drugs testing) and the rescue services (testing for toxic fumes in fires)
