Associated Electrical Industries (AEI), Manchester, England, Mass Spectrometer 9 (MS 9). Thomas Aczel (left) reading chart and H. E. Lumpkin (right) at the operations console, June 1974. CHF Collections.

Critical Mass: A History of Mass Spectrometry

The Center for Oral History at CHF holds a growing collection of mass spectrometry–related oral histories that provides a window into the chronicle of this complex scientific world through personal stories and recollections. The accounts given by interviewees document the work of pioneers in the field and in the vibrant research community, an area that has evolved from a fringe field to a technology and specialization at the heart of several disciplines. But what is mass spectrometry? Few can elaborate further than to call it an extremely technical field related to chemistry and physics, an area full of jargon and science-speak indecipherable to the average person. But mass spectrometry is many things: a field of study, a line of instrumentation, and a community of people. In this online exhibit, we show how this complicated science has played a role in many ways: in the Manhattan Project, in the petroleum industry, in building a community, in biochemical applications, and in the various outstanding technological developments.  

To truly define mass spectrometry, we consulted a professional: “About the best, short, non-technical description of the mass spectrometer is that it weighs molecules, sorts them according to weight, then counts the number of each weight” (Harold Wiley, 1949). In a more technical sense mass spectrometry determines the mass of a molecule by measuring the mass-to-charge ratio of an ion—an atom or molecule carrying a charge as a result of a gain or loss of electrons created from the breaking up of a molecule—and passing it through an electromagnetic field. Molecules are ionized, separated, and detected so that information about molecular mass and even the structure of that molecule can be identified. The instrument and its ability to determine not only mass but the relative abundance of elements and their isotopes (atoms with the same atomic number but different atomic masses owing to differences in the number of neutrons) was groundbreaking in the first half of the 20th century, and intrepid engineers, physicists, and chemists saw opportunities for extending this tool into other areas. And scientists continue to find innovative ways to use these instruments and the data they provide. The technology has become so prevalent that it even appears in cameos on television shows like Star Trek: The Next Generation and CSI.

The meaning of the phrase “mass spectrometry” has changed dramatically over the last 100 years. Today, the technique is embodied by high-tech, computerized instrumentation, but its roots took hold in the 19th century, when gaining knowledge about the substances around us—including, at the most basic level, understanding their mass—became a key factor in understanding the physical world. Comprehending the building blocks of the universe—the elements—required precise mass measurement.

Mass Spectrometry’s origins

J. J. Thomson, a British physicist, brought electrons, isotopes, and mass spectrometry into the scientific conversation beginning in 1897. While other physicists had theorized that there were smaller particles that composed atoms, Thomson, who studied cathode rays, was the first to propose that negatively charged particles 1,000 times smaller than an atom were the smallest building blocks of matter—what we know today to be the electron. About a decade later Thomson took his study of these new particles, which he called corpuscles, and of another topic of interest, canal rays (anode rays, or beams of positive ions), a step farther. Working with an assistant, Francis W. Aston, Thomson channeled ionized neon through both electric and magnetic fields and measured how far the particles were deflected. The particles reflected differently, Aston concluded, because they were different isotopes of neon, meaning they had two different masses. This experiment formed the root of mass spectrometry, and Aston as well as others would expand on these initial studies in the coming decade.

Working in Cambridge, England, Aston improved both Thomson’s methodology and his instrumentation; he is credited with the creation of the first mass-spectrograph instrument in 1919. Using his new device, Aston identified isotopes of mercury and chlorine. He would go on to identify 212 of the 278 naturally occurring isotopes. Concurrently, Arthur Dempster, at the University of Chicago, was investigating isotopes. In 1918 he developed what is considered the first modern mass spectrometer and, like Aston, identified isotopes at a fast pace, including those of magnesium, palladium, gold, and iridium. This early period of innovation, exemplified by the work of Thomson, Aston, and Dempster, provided the groundwork for the incredibly complex and earth-shattering work that would soon follow.

By the 1930s, when isotope separation and identification was standard with the newer models of mass spectrometers, the threat of war would demonstrate mass spectrometry’s use within the scientific community. The 1939 discovery that the nucleus of uranium could be split, releasing an extraordinary amount of energy, was an amazing one. However, it was a discovery that prompted questions only the mass spectrometer could answer. Could this energy be harnessed? Which isotope of uranium was responsible for fission? Young physicist Alfred Nier and his knowledge of mass spectrometry were called upon to determine which isotope of uranium could be split and thus used practically. Nier built a new mass spectrometer for the task and quickly determined that U-235 was the fissionable isotope. The mass spectrometer was a vital piece of early Manhattan Project research.

A page from the manual for the CEC Type 21-104 Mass Spectrometer. Vincent Coates  Instrumentation Ephemera Collection, CHF Collections. Click here for full size.

The dramatic wartime uses of mass spectrometry in the Manhattan Project proved mass spectrometry’s possibilities were only just beginning. Clearly, scientific research that required specific knowledge about the elements required the new technology of mass spectrometry. If the instrumentation could determine the molecular weights of things like isotopes and elements, astute users of the instrumentation predicted that it could also do similar measurements for other areas of chemistry by determining the type of chemicals in a certain sample or compound and the structure of molecules. Frank Field saw the technology go from wartime necessity to commercial success:

But it really started, in my opinion, with the invention of these—or the construction of—these mass spectrometers by the commercial firms. That would be Westinghouse on the one hand and CEC [Consolidated Engineering Corporation] on the other. Of course, for a while, General Electric was in it, and Bendix was in it. But, it was easy to get a mass spectrometer. You could buy it, and it had some instructions as to how to use it. First, the petroleum industry discovered its utility. Mass spectrometry wouldn’t be anywhere without the petroleum industry. (50)

Various companies determined that mass-spectrometry instrumentation was something many labs would want and need. These commercial mass-spectrometry instruments found a large body of customers quickly—initially in the petrochemical industry. Always pursuing faster means of research and testing as well as better profits, oil companies rushed to purchase the latest model, which could assist in determining the contents of a petroleum sample. Chemistry and physics labs nationwide—and worldwide—were turning their attention to mass spectrometry.


Postwar Advances

CEC 21-103

Glyn R. Taylor, operator, prepares a sample for introduction into the heated inlet system of Consolidated Engineering Corporation Model 21-103 Mass Spectrometer, May 1974. CHF Collections.

The work of the post–World War II generation of mass-spectrometry pioneers built on the fundamental discoveries and research of the first half of the 20th century. In the next 50 years the instrumentation would become even more complex and computerized owing to the work of these pioneers. The field was definitively “hands-on”: as young chemists and engineers were given a mass spectrometer to work with, users could make it their own and tailor the equipment for their lab or their company’s own needs. These scientists would often build the instrumentation by hand and modify it by trial and error to achieve the results they wanted. Many of these individuals had no idea what mass spectrometry was until given an instrument. Take, for example, John Beynon’s first exposure to mass spectrometry in 1947:

I went to ICI [Imperial Chemical Industries] and arrived for my first morning, was shown to my desk, and on my desk there was a note that said, “Remit for Mr. Beynon, build a mass spectrometer,” which came as a huge shock to me, because I didn’t really know what a mass spectrometer was.  (19)

But the work of Beynon and others in the field transformed them from chemists or physicists into the first group to call themselves mass spectrometrists, and the field became a vibrant community of collaborators.

New Horizons

As mass spectrometry reached into new fields like biology, new technological advancements also propelled the instrumentation’s capabilities. With medical breakthroughs happening at a fast pace in the second half of the 20th century and developments in biology that revealed the building blocks of life, mass spectrometry again was able to provide new groups—biochemists and biologists—with vital information. Complex biological structures, like nucleic acids, proteins, and carbohydrates, could be identified quickly with mass spectrometry; and the field of proteomics grew at a fast pace with the assistance of mass spectrometry.

Frank Field discusses mass spectrometry's evolution over the years.

For over a century individuals working within an interdisciplinary environment—chemistry, physics, engineering, even mathematics—have built mass spectrometers. Computers have opened quicker, more reliable ways of analyzing the data. Instruments have improved and been combined with various new technologies, amplifying their usefulness. But other aspects of mass spectrometry have been built as well: the community has grown from a small, fledgling collection of individuals developing and working with their own instrumentation into a field that boasts its own professional society and specialists. Today, mass spectrometry’s reach is wide. Fields as diverse as environmental science, biology, astronomy, and geology, among others, rely on mass spectrometry when complex calculations or identification of molecules are necessary. Developments in mass spectrometry have led to Nobel prizes, and a mass spectrometer even made it into space. In 1964, only a few decades removed from the introduction of the first commercial mass spectrometer Alfred Nier explained, "In spite of the furious pace at which research is proceeding these days, the frontiers always seem to grow. In other words, the more we learn, the more we discover needs to be learned." (Nier, The Practicality of the Impractical, 12)  The Center for Oral History’s body of interviewees from mass spectrometry has seen the field evolve from a mysterious technique used only by a select group of physicists to an inexpensive piece of equipment present in nearly every chemistry and biochemistry lab. The Center for Oral History at CHF tells the story of how this discipline was built—and how it helped build other disciplines as well.