Mass spectrometry | Definition, Applications, Principle, & Facts

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class="md-content"> <div class="md-article-container template-desktop infinite-pagination"> <div class="infinite-scroll-container article last"> <article class="article-content container-lg qa-content px-0 pt-0 pb-40 py-lg-20 content md-expanded" data-topic-id="368325"> <div class="grid gx-0"> <div class="col-auto"> <div class="topic-left-rail md-article-drawer position-relative d-flex border-right-sm border-left-sm open"> <div class="drawer d-flex flex-column open"> <div class="left-rail-section-content"> <div class="topic-left-rail-header text-truncate bg-gray-50 position-relative text-right d-flex align-items-center"> <div class="tlr-title px-20 py-15 text-left"> <em class="material-icons text-gray-400 d-lg-none" data-icon="toc"></em> <a class="font-serif font-weight-bold text-black link-blue" href="https://www.britannica.com/science/mass-spectrometry">mass spectrometry</a> </div> <button aria-label="Close" class="js-sections-close-button btn-link btn-sm btn d-lg-none position-absolute top-0 p-10 right-0" > <em class="material-icons font-26" data-icon="close"></em> </button> </div> <div class="section-content pl-10 pr-20 pl-sm-50 pr-sm-60 pl-lg-5 pr-lg-10 pt-10 pt-lg-0 bg-gray-50 clear-catfish-ad"> <div class="toc mb-20"> <div class="font-serif font-14 font-weight-bold mx-15 mb-15 mt-20"> Table of Contents </div> <ul class="list-unstyled my-0" data-level="h1"><li data-target="#ref1"><div class="pl-25"><a class="link-gray-900 w-100" href="/science/mass-spectrometry">Introduction</a></div><div class="ml-40 toc-drawer sub-toc-drawer"></div></li><li data-target="#ref80533"><div class="d-flex align-items-center"><button class="h1-link-drawer-button btn btn-xs btn-circle d-flex rounded" type="button" aria-label="Toggle Heading"><em class="material-icons font-18" data-icon="keyboard_arrow_right"></em></button><a class="w-100 link-gray-900" href="/science/mass-spectrometry#ref80533">History</a></div><div class="ml-40 toc-drawer sub-toc-drawer"><ul class="list-unstyled" data-level="h2"><li data-target="#ref80534"><a class="w-100 link-gray-900" href="/science/mass-spectrometry#ref80534">Focusing spectroscopes</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref80535"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Ion-velocity-spectrometers">Ion-velocity spectrometers</a></li></ul></div></li><li data-target="#ref80536"><div class="d-flex align-items-center"><button class="h1-link-drawer-button btn btn-xs btn-circle d-flex rounded" type="button" aria-label="Toggle Heading"><em class="material-icons font-18" data-icon="keyboard_arrow_right"></em></button><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Ion-velocity-spectrometers#ref80536">General principles</a></div><div class="ml-40 toc-drawer sub-toc-drawer"><ul class="list-unstyled" data-level="h2"><li data-target="#ref80537"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Ion-velocity-spectrometers#ref80537">Ion sources</a><ul class="list-unstyled" data-level="h3"><li data-target="#ref80538"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Ion-velocity-spectrometers#ref80538">Direct-current arc</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref80539"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Ion-velocity-spectrometers#ref80539">Electron bombardment</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref80540"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Thermal-ionization">Thermal ionization</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref80541"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Thermal-ionization#ref80541">Spark discharge</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref80542"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Thermal-ionization#ref80542">Secondary-ion emission</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref80543"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Thermal-ionization#ref80543">Field ionization</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref80544"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Thermal-ionization#ref80544">High-frequency-produced plasma</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref80545"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Thermal-ionization#ref80545">Photoionization</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref80546"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Thermal-ionization#ref80546">Resonance photoionization</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref80547"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Negative-ions">Negative ions</a></li></ul></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref80548"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Negative-ions#ref80548">Sample introduction</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref80549"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Negative-ions#ref80549">Ion-beam analysis</a><ul class="list-unstyled" data-level="h3"><li data-target="#ref80550"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Negative-ions#ref80550">General objectives</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref80551"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Negative-ions#ref80551">Magnetic field analysis</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref80552"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Electrostatic-field-analysis">Electrostatic field analysis</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref80553"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Electrostatic-field-analysis#ref80553">Combined electric and magnetic field analysis</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref80554"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Electrostatic-field-analysis#ref80554"><em>z</em>-axis focusing</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref80555"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Electrostatic-field-analysis#ref80555">Time of flight</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref80556"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Ion-trap-methods">Ion-trap methods</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref80557"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Ion-trap-methods#ref80557">Tandem spectrometry</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref80558"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Ion-trap-methods#ref80558">Quadrupole spectrometer</a></li></ul></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref80559"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Ion-trap-methods#ref80559">Ion beam detection</a><ul class="list-unstyled" data-level="h3"><li data-target="#ref80560"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Ion-trap-methods#ref80560">Photographic plates</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref80561"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Ion-trap-methods#ref80561">Faraday cup</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref80562"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Electron-multipliers">Electron multipliers</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref80563"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Electron-multipliers#ref80563">Daly detector</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref80564"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Electron-multipliers#ref80564">Multiple detectors</a></li></ul></li></ul></div></li><li data-target="#ref80565"><div class="d-flex align-items-center"><button class="h1-link-drawer-button btn btn-xs btn-circle d-flex rounded" type="button" aria-label="Toggle Heading"><em class="material-icons font-18" data-icon="keyboard_arrow_right"></em></button><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Important-technical-adjuncts">Important technical adjuncts</a></div><div class="ml-40 toc-drawer sub-toc-drawer"><ul class="list-unstyled" data-level="h2"><li data-target="#ref80566"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Important-technical-adjuncts#ref80566">Vacuum</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref80567"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Important-technical-adjuncts#ref80567">Electronics</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref80568"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Important-technical-adjuncts#ref80568">Computers</a></li></ul></div></li><li data-target="#ref80569"><div class="d-flex align-items-center"><button class="h1-link-drawer-button btn btn-xs btn-circle d-flex rounded" type="button" aria-label="Toggle Heading"><em class="material-icons font-18" data-icon="keyboard_arrow_right"></em></button><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Important-technical-adjuncts#ref80569">Applications</a></div><div class="ml-40 toc-drawer sub-toc-drawer"><ul class="list-unstyled" data-level="h2"><li data-target="#ref80570"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Important-technical-adjuncts#ref80570">Atomic</a><ul class="list-unstyled" data-level="h3"><li data-target="#ref80571"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Important-technical-adjuncts#ref80571">Atomic masses</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref80572"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Important-technical-adjuncts#ref80572">Geochronology and geochemistry</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref80573"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Hydrogen-carbon-nitrogen-oxygen-and-sulfur-in-nature">Hydrogen, carbon, nitrogen, oxygen, and sulfur in nature</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref80574"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Hydrogen-carbon-nitrogen-oxygen-and-sulfur-in-nature#ref80574">Trace element analysis</a></li></ul></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref80575"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Hydrogen-carbon-nitrogen-oxygen-and-sulfur-in-nature#ref80575">Molecular</a><ul class="list-unstyled" data-level="h3"><li data-target="#ref80576"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Hydrogen-carbon-nitrogen-oxygen-and-sulfur-in-nature#ref80576">Ion-molecule reactions</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref80577"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Hydrogen-carbon-nitrogen-oxygen-and-sulfur-in-nature#ref80577">Organic chemistry</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref80578"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Hydrogen-carbon-nitrogen-oxygen-and-sulfur-in-nature#ref80578">Space probes</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref80579"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Hydrogen-carbon-nitrogen-oxygen-and-sulfur-in-nature#ref80579">Leak detection</a></li></ul></li></ul></div></li><li data-target="#ref80580"><div class="d-flex align-items-center"><button class="h1-link-drawer-button btn btn-xs btn-circle d-flex rounded" type="button" aria-label="Toggle Heading"><em class="material-icons font-18" data-icon="keyboard_arrow_right"></em></button><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Accelerator-mass-spectrometry">Accelerator mass spectrometry</a></div><div class="ml-40 toc-drawer sub-toc-drawer"><ul class="list-unstyled" data-level="h2"><li data-target="#ref80581"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Accelerator-mass-spectrometry#ref80581">Development</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref80582"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Accelerator-mass-spectrometry#ref80582">Operation of the tandem electrostatic accelerator</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref80583"><a class="w-100 link-gray-900" href="/science/mass-spectrometry/Accelerator-mass-spectrometry#ref80583">Applications</a></li></ul></div></li></ul> <a class="toc-extra-link link-gray-900" href="https://www.britannica.com/science/mass-spectrometry/additional-info">References & Edit History</a> <a class="toc-extra-link link-gray-900" href="/facts/mass-spectrometry">Quick Facts & Related Topics</a> </div> <div class="tlr-media-slider pb-10 mb-30"> <a class="section-header link-gray-900 font-serif font-14 font-weight-bold mb-10 mx-10" href="https://www.britannica.com/science/mass-spectrometry/images-videos">Images & Videos</a> <div class="slider js-slider position-relative d-inline-flex align-items-center mw-100 "> <div class="slider-container js-slider-container overflow-hidden d-flex overflow-hidden text-nowrap ml-15"> <a href="https://cdn.britannica.com/91/5691-004-D2E7DF72/electron-bombardment-ion-source-cross-section-region.jpg" data-href="/media/1/368325/3141" class="media-overlay-link d-inline-block mr-5"> <img loading="lazy" src="https://cdn.britannica.com/91/5691-004-D2E7DF72/electron-bombardment-ion-source-cross-section-region.jpg" alt="Figure 1: An electron bombardment ion source in cross section. An electron beam is drawn from the filament and accelerated across the region in which the ions are formed and toward the electron trap. An electric field produced by the repeller forces the ion beam from the source through the exit slit." height="50" /> </a> <a href="https://cdn.britannica.com/93/5693-004-5CA0AE48/Paths-ions-magnetic-field-plane-perpendicular-B.jpg" data-href="/media/1/368325/3137" class="media-overlay-link d-inline-block mr-5"> <img loading="lazy" src="https://cdn.britannica.com/93/5693-004-5CA0AE48/Paths-ions-magnetic-field-plane-perpendicular-B.jpg" alt="Figure 2: Paths of monoenergetic ions moving in a plane perpendicular to a magnetic field, passing through focal point B after originating at point A (see text)." height="50" /> </a> <a href="https://cdn.britannica.com/95/5695-004-86D5D4EC/action-field-ions-beam-electrodes-focus-point.jpg" data-href="/media/1/368325/3138" class="media-overlay-link d-inline-block mr-5"> <img loading="lazy" src="https://cdn.britannica.com/95/5695-004-86D5D4EC/action-field-ions-beam-electrodes-focus-point.jpg" alt="Figure 3: Focusing action of a radial electrostatic field produced by two semicylindrical charged electrodes on a monoenergetic beam of ions. The ions diverging from point A are brought to a focus at point B." height="50" /> </a> <a href="https://cdn.britannica.com/96/5696-004-DDAD36CA/Arrangement-sectors-mass-spectrometer-Mattauch-Herzog-ions-beam.jpg" data-href="/media/1/368325/3139" class="media-overlay-link d-inline-block mr-5"> <img loading="lazy" src="https://cdn.britannica.com/96/5696-004-DDAD36CA/Arrangement-sectors-mass-spectrometer-Mattauch-Herzog-ions-beam.jpg" alt="Figure 4: Arrangement of the electrostatic and magnetic sectors in the Mattauch-Herzog double-focusing mass spectrometer. The ions are deflected in opposite directions in the electrostatic and magnetic fields. The divergent monoenergetic beam contains two ion species of different mass-to-charge ratio. All ions are brought to a focus along the plane AB." height="50" /> </a> <a href="https://cdn.britannica.com/97/5697-004-E0FD514B/Arrangement-direction-sectors-mass-spectrometer-Nier-sector.jpg" data-href="/media/1/368325/3140" class="media-overlay-link d-inline-block mr-5"> <img loading="lazy" src="https://cdn.britannica.com/97/5697-004-E0FD514B/Arrangement-direction-sectors-mass-spectrometer-Nier-sector.jpg" alt="Figure 5: Arrangement of the electrostatic and magnetic sectors in the Nier double-focusing mass spectrometer. The angle of the electrostatic sector is 90° and that of the magnetic sector 60°. The direction of deflection of the ion beam is the same in both sectors." height="50" /> </a> <a href="https://cdn.britannica.com/98/5698-004-D4574C38/diagram-quadrupole-mass-spectrometer-electrodes-pairs-radio.jpg" data-href="/media/1/368325/3142" class="media-overlay-link d-inline-block mr-5"> <img loading="lazy" src="https://cdn.britannica.com/98/5698-004-D4574C38/diagram-quadrupole-mass-spectrometer-electrodes-pairs-radio.jpg" alt="Figure 6: Schematic diagram of a quadrupole mass spectrometer. The pairs of opposing electrodes are electrically connected to a balanced voltage source having a radio frequency component superimposed on a constant potential. Combinations of values for the amplitude and frequency exist that allow ions of a given mass from a beam of constant energy to emerge undeflected." height="50" /> </a> <a href="https://cdn.britannica.com/99/5699-004-CB000B59/spectrum-osmium-Os-recorder-trace-electron-multiplier.jpg" data-href="/media/1/368325/3143" class="media-overlay-link d-inline-block mr-5"> <img loading="lazy" src="https://cdn.britannica.com/99/5699-004-CB000B59/spectrum-osmium-Os-recorder-trace-electron-multiplier.jpg" alt="Figure 7: The mass spectrum of osmium. This recorder trace was obtained with an electron multiplier detecting OsO3−. The leftmost and rightmost peaks were recorded with the detector gain set at a value 100 times that used for the rest of the spectrum; this change is marked by the change in the baseline position. The small satellite peaks to the left are those of the low abundance oxygen isotopes 17O and 18O; the osmium isotopes are, from left to right, 184Os, 186Os, 188Os, 189Os, 190Os, and the satellite peaks of 192Os." height="50" /> </a> <a href="https://cdn.britannica.com/00/5700-004-86C755A2/diagram-application-accelerator-mass-spectrometer-ion-trajectories.jpg" data-href="/media/1/368325/3148" class="media-overlay-link d-inline-block mr-5"> <img loading="lazy" src="https://cdn.britannica.com/00/5700-004-86C755A2/diagram-application-accelerator-mass-spectrometer-ion-trajectories.jpg" alt="Figure 8: Schematic diagram showing the ion trajectories in an accelerator mass spectrometer with application to 10Be. Negative ions of BeO leave the source and are mass analyzed with 10BeO− directed into the accelerator and 9BeO− into a Faraday cup. The molecular ions are broken up by gas and a thin carbon foil in the high-voltage terminal with much of the 10Be ionized to the 3+ charge state. The emerging ions pass through a velocity selector, are again analyzed for mass, and pass to the detector. Velocity selection is attained by a magnetic field and an electric field that are orthogonal to one another and to the beam direction; they are adjusted so that no deflection takes place for ions of the desired velocity." height="50" /> </a> <a href="https://cdn.britannica.com/09/7409-004-FC74091C/Mass-spectrometry-structure-compounds-2-butanone-ions-compound.jpg" data-href="/media/1/368325/69" class="media-overlay-link d-inline-block mr-5"> <img loading="lazy" src="https://cdn.britannica.com/09/7409-004-FC74091C/Mass-spectrometry-structure-compounds-2-butanone-ions-compound.jpg" alt="mass spectrum of 2-butanone" height="50" /> </a> <a href="/video/research-fingerprints/207679" data-href="/media/1/368325/207679" class="media-overlay-link d-inline-block mr-5"> <div class="position-relative --aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/17/187017-138-9CF1485B/research-fingerprints.jpg?w=400&h=225&c=crop" alt="A real-life forensic technique: Aging fingerprints" class="col-100" /> <div class="btn btn-sm btn-white btn-circle position-absolute shadow" style="top: 50%; left:50%; transform: translate(-50%, -50%)"> <em class="material-icons font-14" data-icon="play_arrow" > </em> </div> </div> </a> </div> <button disabled class="prev-button js-prev-button position-absolute btn btn-circle shadow btn-blue " aria-label="Previous"> <span class="material-icons md-24" data-icon="keyboard_arrow_left"></span> </button> <button disabled class="next-button js-next-button position-absolute btn btn-circle shadow btn-blue " aria-label="Next"> <span class="material-icons md-24" data-icon="keyboard_arrow_right"></span> </button> </div> </div> <div class="mb-30 tlr-student-links"> <div class="text-gray-900 p-5 font-serif font-14 font-weight-bold mx-10 mb-10"> For Students </div> <div class="imagelink-with-image-on-the-side card card-horizontal tlr-img-with-side-link ml-15 link-gray-900 mb-10" > <div class="position-relative card-media" style="flex: 0;"> <a class="ilf-image position-relative" href="/summary/mass-spectrometry"> <img loading="lazy" src="https://cdn.britannica.com/mendel-resources/3-130/images/shared/default3.png?v=3.130.14" class="default " height="200" width="200"/> </a> </div> <div class="card-body ilf-content"> <a class="font-weight-semi-bold d-block mb-5 font-16 ilf-title" href="/summary/mass-spectrometry" >mass spectrometry summary</a> </div> </div> </div> <div class="mb-30 tlr-discover"> <div class="text-gray-900 p-5 font-serif font-14 font-weight-bold mx-10 mb-10"> Discover </div> <div class="imagelink-with-image-on-the-side card card-horizontal tlr-img-with-side-link ml-15 link-gray-900 mb-10" > <div class="position-relative card-media" style="flex: 0;"> <a class="ilf-image position-relative" href="/list/10-greatest-baseball-players-of-all-time"> <img loading="lazy" src="https://cdn.britannica.com/35/146135-131-BC5E7D00/Baseball-grass-arts-Homepage-blog-entertainment-sports-2010.jpg?w=200&h=200&c=crop" alt="Baseball laying in the grass. 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Author of <i>Mass Spectrometry and Its Application to Organic Chemistry.</i></div> </a> <div data-popper-arrow></div> </div> <span class="btn btn-link editor-link p-0 qa-byline-link gtm-byline font-12 byline-contributor text-decoration-underline"> John Herbert Beynon</span>, <div class="editor-popover popover p-0"> <a class="d-block p-20 gtm-byline font-12 byline-contributor" href="/contributor/Louis-Brown/3914" > <div class="editor-title font-16 font-weight-bold">Louis Brown</div> <div class="editor-description font-12 font-serif mt-5 clamp-description text-black">Emeritus staff member, Department of Terrestrial Magnetism, Carnegie Institution of Washington, D.C.</div> </a> <div data-popper-arrow></div> </div> <span class="btn btn-link editor-link p-0 qa-byline-link gtm-byline font-12 byline-contributor text-decoration-underline"> Louis Brown</span><span class="text-gray-700 mx-5">•</span><a class="see-all border-gray-700 gtm-byline" rel="nofollow" href="https://www.britannica.com/science/mass-spectrometry/additional-info#contributors">All</a> </div> <div class="font-serif font-12 text-gray-700"> <span class="qa-fact-checked-by">Fact-checked by</span> <div class="editor-popover popover p-0"> <a class="d-block p-20 font-12" href="/editor/The-Editors-of-Encyclopaedia-Britannica/4419" > <div class="editor-title font-16 font-weight-bold">The Editors of Encyclopaedia Britannica</div> <div class="editor-description font-12 font-serif mt-5 text-black">Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree. They write new content and verify and edit content received from contributors.</div> </a> <div data-popper-arrow></div> </div> <span class="btn btn-link editor-link p-0 qa-byline-link font-12 "> The Editors of Encyclopaedia Britannica</span></div> <div class="last-updated font-12 font-serif"> <span class="text-gray-700"> Last Updated: <time datetime="2024-10-18T00:00:00CDT" >Oct 18, 2024</time> •</span> <a class="byline-edit-history" href="https://www.britannica.com/science/mass-spectrometry/additional-info#history" rel="nofollow">Article History</a> </div></div> </div> <button class="d-flex d-lg-none btn btn-outline-blue border rounded-sm shadow-sm mobile-toc-button gtm-mobile-toc-inline-button d-none d-sm-block js-sections-inline-button module-spacing btn d-lg-none"> <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="toc"></em> Table of Contents </button> <div class="d-flex d-sm-none flex-row"> <button class="d-flex d-lg-none btn btn-outline-blue border rounded-sm shadow-sm mobile-toc-button gtm-mobile-toc-inline-button js-sections-inline-button module-spacing"> <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="toc"></em> Table of Contents </button> <button class="ai-ask-button btn border-2 ai-ask-button btn border-2 module-spacing btn-sm js-inline-ai-ask-button btn-outline-red-400 border-red-400 p-10 ml-5"> Ask the Chatbot a Question </button> </div> <div class="js-qf-module qf-module px-40 px-sm-20 py-15 mx-auto module-spacing font-14 bg-gray-50 rounded"> <div class="facts-list mt-10"> <div class=""> <div class="js-fact mb-10 line-clamp clamp-3"> <dl> <dt>Also called: </dt> <dd>mass spectroscopy</dd> </dl> <button class="js-more-btn d-none btn btn-unstyled font-12 bg-gray-50" aria-label="Toggle more/less fact data"> <em class="js-content link-blue">(Show more)</em> </button> </div> </div> <div class=""> <div class="js-fact mb-10 line-clamp clamp-3"> <dl> <dt>Key People: </dt> <dd><a href="/biography/John-Fenn" topicid="891299">John B. Fenn</a></dd> <dd><a href="/biography/Tanaka-Koichi" topicid="891322">Tanaka Koichi</a></dd> <dd><a href="/biography/Francis-William-Aston" topicid="39838">Francis William Aston</a></dd> <dd><a href="/biography/Arthur-Jeffrey-Dempster" topicid="157489">Arthur Jeffrey Dempster</a></dd> </dl> <button class="js-more-btn d-none btn btn-unstyled font-12 bg-gray-50" aria-label="Toggle more/less fact data"> <em class="js-content link-blue">(Show more)</em> </button> </div> </div> <div class=""> <div class="js-fact mb-10 line-clamp clamp-3"> <dl> <dt>Related Topics: </dt> <dd><a href="/science/ion-trap-mass-spectrometry" topicid="292854">ion-trap mass spectrometry</a></dd> <dd><a href="/science/secondary-ion-mass-spectrometry" topicid="531734">secondary ion mass spectrometry</a></dd> <dd><a href="/science/resonance-ionization-mass-spectrometry" topicid="499442">resonance-ionization mass spectrometry</a></dd> <dd><a href="/science/mass-spectroscope" topicid="368354">mass spectroscope</a></dd> <dd><a href="/science/mass-spectrum" topicid="368362">mass spectrum</a></dd> </dl> <button class="js-more-btn d-none btn btn-unstyled font-12 bg-gray-50" aria-label="Toggle more/less fact data"> <em class="js-content link-blue">(Show more)</em> </button> </div> <div class="text-center"> <a class="btn btn-sm btn-link p-0" href="/facts/mass-spectrometry"> See all related content </a> </div> </div> </div> </div><span class="marker before-article"></span><section data-level="1" id="ref1"><span class="marker PREMOD1 mod-inline"></span><p class="topic-paragraph"><strong><span id="ref619838"></span>mass spectrometry</strong>, <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="analytic" href="https://www.merriam-webster.com/dictionary/analytic" data-type="MW">analytic</a> technique by which chemical substances are identified by the sorting of gaseous <span id="ref619839"></span><a href="https://www.britannica.com/science/ion-physics" class="md-crosslink " data-show-preview="true">ions</a> in electric and magnetic fields according to their <span id="ref619840"></span><a href="https://www.britannica.com/science/mass-to-charge-ratio" class="md-crosslink ">mass-to-charge ratios</a>. The <span id="ref619841"></span><a href="https://www.britannica.com/technology/instrumentation-technology" class="md-crosslink " data-show-preview="true">instruments</a> used in such studies are called <span id="ref619842"></span><a href="https://www.britannica.com/science/mass-spectrometer" class="md-crosslink ">mass spectrometers</a> and <span id="ref619843"></span><a href="https://www.britannica.com/science/mass-spectrograph" class="md-crosslink ">mass spectrographs</a>, and they operate on the principle that moving ions may be deflected by electric and magnetic fields. The two instruments differ only in the way in which the sorted charged particles are detected. In the mass <a href="https://www.britannica.com/science/spectrometer" class="md-crosslink autoxref " data-show-preview="true">spectrometer</a> they are detected electrically, in the mass spectrograph by photographic or other nonelectrical means; the term <span id="ref619844"></span><a href="https://www.britannica.com/science/mass-spectroscope" class="md-crosslink ">mass spectroscope</a> is used to include both kinds of devices. Since electrical detectors are now most commonly used, the field is typically referred to as mass spectrometry.</p><span class="marker MOD1 mod-inline"></span><span class="marker PREMOD2 mod-inline"></span><p class="topic-paragraph">Mass spectroscopes consist of five basic parts: a high vacuum system; a sample handling system, through which the sample to be investigated can be introduced; an <a href="https://www.britannica.com/science/ion-physics" class="md-crosslink autoxref " data-show-preview="true">ion</a> source, in which a <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="beam" href="https://www.britannica.com/dictionary/beam" data-type="EB">beam</a> of charged particles characteristic of the sample can be produced; an analyzer, in which the beam can be separated into its components; and a detector or receiver by means of which the separated ion beams can be observed or collected.</p><span class="marker MOD2 mod-inline"></span><span class="marker PREMOD3 mod-inline"></span><p class="topic-paragraph">Many investigations have been conducted with the help of mass spectrometry. These include the identification of the isotopes of the chemical elements and determination of their precise masses and relative abundances, the dating of geologic samples, the analysis of inorganic and organic chemicals especially for small amounts of impurities, structural formula determination of complex organic substances, the strengths of chemical bonds and energies necessary to produce particular ions, the identification of products of ion decomposition, and the analysis of unknown materials, such as lunar samples, for their chemical and isotopic <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="constituents" href="https://www.merriam-webster.com/dictionary/constituents" data-type="MW">constituents</a>. Mass spectroscopes also are employed to separate isotopes and to measure the abundance of concentrated isotopes when used as tracers in <a href="https://www.britannica.com/science/chemistry" class="md-crosslink autoxref " data-show-preview="true">chemistry</a>, biology, and <a href="https://www.britannica.com/science/medicine" class="md-crosslink autoxref " data-show-preview="true">medicine</a>.</p><span class="marker MOD3 mod-inline"></span></section> <span class="marker h2"></span><section data-level="1" id="ref80533"> <h2 class="h1">History</h2> <span class="marker PREMOD4 mod-inline"></span><p class="topic-paragraph">The foundation of mass spectroscopy was laid in 1898, when <a href="https://www.britannica.com/biography/Wilhelm-Wien" class="md-crosslink autoxref " data-show-preview="true">Wilhelm Wien</a>, a German physicist, discovered that beams of charged particles could be deflected by a <span id="ref619846"></span><a href="https://www.britannica.com/science/magnetic-field" class="md-crosslink " data-show-preview="true">magnetic field</a>. In more refined experiments carried out between 1907 and 1913, the British physicist <span id="ref619847"></span><a href="https://www.britannica.com/biography/J-J-Thomson" class="md-crosslink " data-show-preview="true">J.J. Thomson</a>, who had already discovered the <span id="ref619848"></span><a href="https://www.britannica.com/science/electron" class="md-crosslink " data-show-preview="true">electron</a> and observed its deflection by an <span id="ref619849"></span><a href="https://www.britannica.com/science/electric-field" class="md-crosslink " data-show-preview="true">electric field</a>, passed a beam of positively charged <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="ions" href="https://www.britannica.com/dictionary/ions" data-type="EB">ions</a> through a combined electrostatic and magnetic field. The two fields in Thomson’s tube were situated so that the ions were deflected through small angles in two perpendicular directions. The net result was that the ions produced a series of parabolic curves on a photographic plate placed in their paths. Each parabola corresponded to ions of a particular mass-to-charge ratio with the specific position of each ion dependent on its velocity; the lengths of the parabolic curves provided a measure of the range of ion energies contained in the beam. Later, in an attempt to estimate the relative abundances of the various ion species present, Thomson replaced the photographic plate with a <a href="https://www.britannica.com/science/metal-chemistry" class="md-crosslink autoxref " data-show-preview="true">metal</a> sheet in which was cut a parabolic slit. By varying the magnetic field, he was able to scan through a <span id="ref619850"></span><a href="https://www.britannica.com/science/mass-spectrum" class="md-crosslink ">mass spectrum</a> and measure a <a href="https://www.britannica.com/science/electric-current" class="md-crosslink autoxref " data-show-preview="true">current</a> corresponding to each separated <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="ion" href="https://www.britannica.com/dictionary/ion" data-type="EB">ion</a> species. Thus he may be credited with the construction of the first mass spectrograph and the first mass spectrometer.</p><span class="marker MOD4 mod-inline"></span> <span class="marker PREMOD5 mod-inline"></span><p class="topic-paragraph">The most noteworthy observation made with the parabola spectrography was the spectrum of rare gases present in the atmosphere. In addition to <span id="ref619851"></span><a href="https://www.britannica.com/science/spectral-line" class="md-crosslink ">lines</a> due to helium (mass 4), neon (mass 20), and argon (mass 40), there was a line corresponding to an ion of mass 22 that could not be attributed to any known <a href="https://www.britannica.com/science/gas-state-of-matter" class="md-crosslink autoxref " data-show-preview="true">gas</a>. The existence of forms of the same element with different masses had been suspected since it had been found that many pairs of radioactive materials could not be separated by chemical means. The name <span id="ref619852"></span><a href="https://www.britannica.com/science/isotope" class="md-crosslink " data-show-preview="true">isotope</a> (from the Greek for “same place”) was suggested by the British chemist <span id="ref619853"></span><a href="https://www.britannica.com/biography/Frederick-Soddy" class="md-crosslink " data-show-preview="true">Frederick Soddy</a> in 1913 for these different radioactive forms of the same chemical species, because they could be classified in the same place in the <a href="https://www.britannica.com/science/periodic-table" class="md-crosslink autoxref " data-show-preview="true">periodic table of the elements</a>. The ion of mass 22 was, in fact, a stable heavy isotope of neon.</p><div class="module-spacing"> </div><span class="marker MOD5 mod-inline"></span> <section data-level="2" id="ref80534"> <h2 class="h2"><span id="ref619854"></span>Focusing spectroscopes</h2> <span class="marker PREMOD6 mod-inline"></span><p class="topic-paragraph">The spectroscopes discussed so far are <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="analogous" href="https://www.merriam-webster.com/dictionary/analogous" data-type="MW">analogous</a> to the pinhole camera in optics, because no focusing of the ion beams is involved. The introduction of focusing types of mass spectroscopes came in the years 1918–19 and was due to the British chemist and physicist <span id="ref619855"></span><a href="https://www.britannica.com/biography/Francis-William-Aston" class="md-crosslink " data-show-preview="true">Francis W. Aston</a> and to the American physicist <span id="ref619856"></span><a href="https://www.britannica.com/biography/Arthur-Jeffrey-Dempster" class="md-crosslink " data-show-preview="true">Arthur J. Dempster</a>.</p><span class="marker MOD6 mod-inline"></span> <span class="marker PREMOD7 mod-inline"></span><p class="topic-paragraph">In Aston’s version, successive electric and magnetic fields were arranged in such a way that all perfectly collimated ions of one mass were brought to a focus independent of their <a href="https://www.britannica.com/science/velocity" class="md-crosslink autoxref " data-show-preview="true">velocity</a>, thus giving rise to what is known as <span id="ref619857"></span>velocity focusing. Aston’s design was the basis of his later instruments with which he systematically and accurately measured the masses of the isotopes of many of the elements. He chose <sup>16</sup>O (the isotope of oxygen of mass 16) as his standard of mass.</p><div class="module-spacing"> <DIV class="marketing-INLINE_SUBSCRIPTION marketing-content" data-marketing-id="INLINE_SUBSCRIPTION"><style> .student-promo-banner-wrapper { container-type: inline-size; margin-bottom: 15px; } @container (min-width: 475px) { .student-promo-banner { flex-direction: row; } .student-promo-banner-img-wrapper { margin-bottom: 0; margin-right: 10px; justify-content: flex-start; } .student-promo-banner-text-wrapper { text-align: left; margin-bottom: 0px; margin-left: 10px; } .student-promo-banner-button-wrapper { margin-right: 0; } }</style> <div class="student-promo-banner-wrapper"> <div class="student-promo-banner d-flex flex-column align-items-center bg-blue rounded p-20"> <div class="student-promo-banner-img-wrapper mb-20 mr-0 d-flex justify-content-center"> <img class="rounded" style="max-width: 100px; min-width: 80px" src="https://cdn.britannica.com/marketing/BlueThistle.webp" /> </div> <div class="student-promo-banner-text-wrapper ml-0 mb-10 text-center text-white"> <div class="h2 mb-10">Get Unlimited Access</div> <div class="h4 font-weight-semi-bold">Try Britannica Premium for free and discover more.</div> </div> <div class="student-promo-banner-button-wrapper d-flex justify-content-center align-items-center ml-auto mr-auto"> <a class="btn btn-m btn-orange" href="https://premium.britannica.com/premium-membership/?utm_source=premium&utm_medium=inline-cta&utm_campaign=black-friday-2024">Subscribe</a> </div> </div> </div> </DIV></div><span class="marker MOD7 mod-inline"></span> <span class="marker PREMOD8 mod-inline"></span><p class="topic-paragraph">Dempster’s spectrometer utilized only a magnetic field, which deflected the ion beam through an arc of 180°. In Dempster’s machine, an ion beam <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="homogeneous" href="https://www.merriam-webster.com/dictionary/homogeneous" data-type="MW">homogeneous</a> in mass and energy but diverging from a slit could be brought to a direction focus. This spectrometer was employed by Dempster to make accurate determinations of the abundances of the isotopes of magnesium, lithium, potassium, calcium, and zinc, laying the foundation for similar measurements of the isotopes of all the elements.</p><div class="one-good-fact-module"> </div><span class="marker MOD8 mod-inline"></span> <span class="marker PREMOD9 mod-inline"></span><p class="topic-paragraph">The resolving power, or <span id="ref619858"></span><a href="https://www.britannica.com/science/resolution-physics" class="md-crosslink ">resolution</a>, of a mass spectroscope is a measure of its ability to separate <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="adjacent" href="https://www.merriam-webster.com/dictionary/adjacent" data-type="MW">adjacent</a> masses that are displayed as peaks on the detector. If two peaks due to mass <em>m</em> and (<em>m</em> + Δ<em>m</em>) can just be separated, the resolving power is <em>m</em>/Δ<em>m</em>. The early machines had resolving powers of only a few hundred. In 1935 and 1936, Dempster, Kenneth T. Bainbridge, both working in the <a href="https://www.britannica.com/place/United-States" class="md-crosslink autoxref " data-show-preview="true">United States</a>, and <span id="ref619859"></span><a href="https://www.britannica.com/biography/Josef-Heinrich-Elizabeth-Mattauch" class="md-crosslink ">Josef Mattauch</a>, in Germany, independently developed instruments with electric and magnetic fields arranged in <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="tandem" href="https://www.britannica.com/dictionary/tandem" data-type="EB">tandem</a> in such a way that ion beams that emerged from the source slits in divergent directions and with different velocities were refocused. Such focusing is termed <span id="ref619860"></span><a href="https://www.britannica.com/science/double-focusing-mass-spectrometer" class="md-crosslink ">double focusing</a>. It was thus possible to achieve a resolving power of about 60,000.</p><span class="marker MOD9 mod-inline"></span> </section> </section><span class="marker end-of-content"></span><span class="marker after-article"></span></div> <div id="chatbot-root"></div> </div> </div> </div> <div class="ai-dialog-placeholder"></div> </div> </div> <aside class="col-md-da-320"></aside> </div> </div> </div> </div> </article></div> </div></div> </div> </main> <div id="md-footer"></div> <noscript><iframe src="//www.googletagmanager.com/ns.html?id=GTM-5W6NC8" height="0" width="0" style="display:none;visibility:hidden"></iframe></noscript> <script type="text/javascript" id="_informizely_script_tag"> var IzWidget = IzWidget || {}; (function (d) { var scriptElement = d.createElement('script'); scriptElement.type = 'text/javascript'; scriptElement.async = true; scriptElement.src = "https://insitez.blob.core.windows.net/site/f780f33e-a610-4ac2-af81-3eb184037547.js"; var node = d.getElementById('_informizely_script_tag'); node.parentNode.insertBefore(scriptElement, node); } )(document); </script>  <script> window.ap3c = window.ap3c || {}; var ap3c = window.ap3c; ap3c.cmd = ap3c.cmd || []; ap3c.cmd.push(function() { ap3c.init('ZO4siT4cLwnykPnzZWJtd3Byb2Q', 'https://engage.email.britannica.com/'); ap3c.track({v: 0}); }); ap3c.activity = function(act) { ap3c.act = (ap3c.act || []); ap3c.act.push(act); }; var s, t; s = document.createElement('script'); s.type = 'text/javascript'; s.src = "https://engage.email.britannica.com/app.js"; t = document.getElementsByTagName('script')[0]; t.parentNode.insertBefore(s, t); </script> <script class="marketing-page-info" type="application/json"> {"pageType":"Topic","templateName":"DESKTOP","pageNumber":1,"pagesTotal":10,"pageId":368325,"pageLength":1053,"initialLoad":true,"lastPageOfScroll":false} </script> <script class="marketing-content-info" type="application/json"> [] </script> <script src="https://cdn.britannica.com/mendel-resources/3-130/js/libs/jquery-3.5.0.min.js?v=3.130.14"></script> <script type="text/javascript" data-type="Init Mendel Code Splitting"> (function() { $.ajax({ dataType: 'script', cache: true, url: 'https://cdn.britannica.com/mendel-resources/3-130/dist/topic-page.js?v=3.130.14' }); })(); </script> <script class="analytics-metadata" type="application/json"> {"leg":"C","adLeg":"C","userType":"ANONYMOUS","pageType":"Topic","pageSubtype":null,"articleTemplateType":"PAGINATED","gisted":false,"pageNumber":1,"hasSummarizeButton":false,"hasAskButton":false} </script> <script type="text/javascript"> EBStat={accountId:-1,hostnameOverride:'webstats.eb.com',domain:'www.britannica.com', json:''}; </script> <script type="text/javascript"> ( function() { $.ajax( { dataType: 'script', cache: true, url: '//www.britannica.com/webstats/mendelstats.js?v=1' } ) .done( function() { try {writeStat(null,EBStat);} catch(err){} } ); })(); </script> <div id="bc-fixed-dialogue"></div> </body> </html>

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Mass spectrometry | Definition, Applications, Principle, & Facts | Britannica