How did mass spectrometry originate?

      The technique of mass spectrometry had its beginnings in J.J. Thomson's vacuum tube where in the early part of the century the existence of electrons and "positive rays" was demonstrated. Thomson, the physicist, observed in his book "Rays of Positive Electricity and Their Application to Chemical Analysis" that the new technique could be a used profitably by chemists to analyze chemicals. Despite this far-sighted observation, the primary application of mass spectrometry remain in the realm of physics for nearly thirty years. It was used to discover a number of isotopes, to determine the relative abundance of the isotopes, and to measure their "exact masses", i.e., atomic masses to within a precision of 1 part in 10⁶ or better. These important fundamental measurements laid the foundation for later developments in diverse feilds ranging from geochronology to biochemical research.

      On these Web pages we discuss the basic principles of mass spectrometry and some important applications. We also provide a brief explanation of how a mass spectrometer works, a description of its various component parts, and a discussion of mass spectra and the kind of information they contain. In later sections we will discuss ionization techniques, data presentation as it relates to chromatography, and some highlights of recent breakthroughs.

      Because mass spectrometry is most often used to analyze organic molecules, the examples on these pages are drawn from this group of substances. The principles of mass spectrometry are, however , broadly applicable and our discussion will also include analyses of inorganic substances.