Isotope Ratio Mass Spectrometry

With the separation of two of the three stable isotopes of neon by Sir J.J. Thomson in 1913, mass spectrometers have continued to be the instrument of choice for measuring ratios of isotope abundances. The first magnetic sector mass spectrometer specifically dedicated to this task was designed by A.O. Nier in 1947 and featured simultaneous collection of ion currents. Many diverse instruments have evolved from this design. Decades of development of sample preparation techniques have realized isotope ratio data from many elements in solids, liquids, and gases. Coupling of devices such as gas chromatographs, combustion apparati, and laser probes to mass spectrometers in concert with computer control, have realized features such as unattended operation, compound-specific isotope analyses and isotopic data spatially resolved over distances of a few micrometers on solid surfaces. Today, applications of isotope ratio mass spectrometry (IRMS) embrace many disciplines with topics such as paleodiets, food adulteration, paleoclimatology, migration of birds and animals, pollutant tracing, ore and oil deposits, meteorology, energy expenditure of animals, including astronauts, and the origin of the universe.