Mass spectrometry is an art of measuring the weights of atoms and molecules. It has emerged as a powerful micro analytical technique not only in determining the molecular weight but also in structural elucidation. Mass spectrum of a compound is its “chemical fingerprint” as each class of compound possesses its own characteristic spectrum.
The origin of mass spectrometry is from the discovery of positive rays in gas discharge tube experiments to study the conduction of electricity by gases at very low pressure. Eugen Goldstein in his experiments on discharge tube using perforated cathode found that there are a beam of positively charged particles originating from the anode, moving towards the cathode. He called these as “Kanalstrahlen” meaning Canal rays. Wilhem Wien found that these rays can be deflected by electric and magnetic fields according to their mass to charge (m/z) ratio. The m/z ratio of the particles in the canal rays were found to depend on the nature of the gas taken in the discharge tube.
J.J. Thomson carried out further experiments on these positive rays to find out the particle responsible for the positive charge. He found that each element possesses its own characteristic positive ion and some possess more than one. This led to the discovery of isotopes. Thomson discovered two isotopes of neon, 20Ne and 22Ne. He isolated these isotopes using his positive ray parabolae apparatus, the first mass spectrometer in history. He applied electric and magnetic fields to the positive rays generated in the discharge tube in a perpendicular fashion, which separated the ions according to the m/z ratio.
Later on Francis William Aston improved the positive ray parabolae apparatus and built his mass spectrograph, the ancestor of modern spectrometers. He subjected the ions to electric and magnetic fields separately making the ions to deflect and focus on a particular point on the photographic plate. Thus he could scan a particular mass range by adjusting the fields.
Earlier the mass spectrometers were predominantly used by inorganic chemists to discover and characterize different isotopes of elements. It was observed that there were background spectra which were characteristic of the lubricants and other organic fluids associated with the instrument. There begins organic mass spectrometry.
Now there has been an explosion of knowledge in the field of mass analysis. Mass spectrographs became mass spectrometers. Now it can be used to get structural information of a wide range of molecules including biomolecules which is made possible by the development of different ionization techniques. The first application of mass spectrometry to amino acids and polypeptides was reported in 1958 by Carl-Ove Andersson.
Nowadays mass spectrometers are used as detecting systems in chromatographic techniques in the so called hyphenated techniques- GC-MS, LC-MS etc. Being the combination of two micro analytical techniques, they are superior to the conventional mass spectrometry. By the advent of tandem mass spectrometry, it is now possible to take the mass spectrum of a mass spectrum.