Originally, mass spectrometry was developed as a tool for physico-chemical investigations, e.g. isotope separation. In 1886, EUGEN GOLDSTEIN[24] discovered, that cathodes not only emit cathode rays, but also an other kind of rays in the opposite direction, called canal rays. Ten years later, SIR JOSEPH J. THOMSON[5] recognised that these canal rays must be composed of positively charged material and developed the first mass spectrograph, recording the parabolic deflections of ``positive rays'' with photographic plates. Almost 30 years later, in 1913, FRANCIS ASTON[5] constructed the first mass spectrograph with velocity focusing, focusing the beam of ions with the same mass-to-charge ratio (m/z) at the same spot on the detector (photo plate). Being used mainly for physical investigations, mass spectrometric techniques were introduced into the chemical industry in the 1930s, especially for product analysis and in petrochemistry.
With the development of high resolution mass spectrometers, the technique was introduced into biochemistry and became an established analytical method. The development of soft ionisation techniques (see 1.1.2.1) especially enhanced the range of possible applications.