Mass spectrometry

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Mass spectrometry (MS) is an analytical chemistry technique that helps identify and quantify chemical compounds in a sample by measuring the mass-to-charge ratio and abundance of gas-phase ions.


Francis William Aston
From Thomson's Rays of Positive Electricity and Their Application to Chemical Analyses (1913)
  • I was fortunate enough to hit on the focussing principle used in the mass spectrograph
  • It has long been known that the chemical atomic weight of hydrogen was greater than one-quarter of that of helium, but so long as fractional weights were general there was no particular need to explain this fact, nor could any definite conclusions be drawn from it.
    • Francis W. Aston, Nobel Lecture (1922)
  • Since it is a close analogue of the ordinary spectrograph and gives a spectrum depending upon mass alone, the instrument is called a mass spectrograph and the spectrum it produces a mass spectrum.
    • Francis W. Aston, Nobel Lecture (1922)
  • Should the research worker of the future discover some means of releasing this [atomic] energy in a form which could be employed, the human race will have at its command powers beyond the dreams of scientific fiction
    • Francis W. Aston, Nobel Lecture (1922)
  • We learned to make elephants fly.
  • In small-molecule mass spectrometry, molecules are first ionized by collision with a high-energy electron beam. The ions then fragment into smaller pieces, which are magnetically sorted according to their mass-to-charge ratio (m/z). The ionized sample molecule is called the molecular ion, M1, and measurement of its mass gives the molecular weight of the sample. Structural clues about unknown samples can be obtained by interpreting the fragmentation pattern of the molecular ion. Mass-spectral fragmentations are usually complex, however, and interpretation is often difficult. In biological mass spectrometry, molecules are protonated using either electrospray ionization (ESI) or matrix-assisted laser desorption ionization (MALDI), and the protonated molecules are separated by time-of-flight (TOF).
    • John McMurry, Organic Chemistry 8th ed. (2012), Ch. 12. Structure Determination: Mass Spectrometry and Infrared Spectroscopy
  • I feel sure that there are many problems in Chemistry which could be solved with far greater ease by this than by any other method. The method is surprisingly sensitive — more so even than that of Spectrum Analysis, requires an infinitesimal amount of material, and does not require this to be specially purified: the technique is not difficult if appliances for high vacua are available.
    • Joseph John Thomson, Rays of Positive Electricity and Their Application to Chemical Analyses (1913)
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