Mass spectrometry (MS) is an analytical technique that ionizes chemical species and sorts the ions based on their mass to charge ratio.
In simpler terms, a mass spectrum measures the masses within a sample.
These spectra are used to determine the elemental or isotopic signature of a sample, the masses of particles and of molecules, and to elucidate the chemical structures of molecules, such as peptides and other chemical compounds.In a typical MS procedure, a sample, which may be solid, liquid, or gas, is ionized, for example by bombarding it with electrons.This may cause some of the sample's molecules to break into charged fragments.These ions are then separated according to their mass-to-charge ratio, typically by accelerating them and subjecting them to an electric or magnetic field: ions of the same mass-to-charge ratio will undergo the same amount of deflection.The ions are detected by a mechanism capable of detecting charged particles, such as an electron multiplier.
Results are displayed as spectra of the relative abundance of detected ions as a function of the mass-to-charge ratio.The atoms or molecules in the sample can be identified by correlating known masses to the identified masses or through a characteristic fragmentation pattern.In 1886, Eugen Goldstein observed rays in gas discharges under low pressure that traveled away from the anode and through channels in a perforated cathode, opposite to the direction of negatively charged cathode rays (which travel from cathode to anode).Goldstein called these positively charged anode rays "Kanalstrahlen"; the standard translation of this term into English is "canal rays".Wilhelm Wien found that strong electric or magnetic fields deflected the canal rays and, in 1899, constructed a device with parallel electric and magnetic fields that separated the positive rays according to their charge-to-mass ratio (Q/m). Thomson later improved on the work of Wien by reducing the pressure to create the mass spectrograph.Wien found that the charge-to-mass ratio depended on the nature of the gas in the discharge tube. Early spectrometry devices that measured the mass-to-charge ratio of ions were called mass spectrographs which consisted of instruments that recorded a spectrum of mass values on a photographic plate.