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As opposed to the other spectrometric methods that have been discussed, mass spectrometry, is not involved with the absorption of electromagnetic radiation and, consequently, is an entirely different type of analytical technique. The pioneers in the development of mass spectrometry were, Thomson (1), Aston (2) and Dempster (3). Basically, mass spectrometry involves first, the production of ions from the sample and these ions can be molecular ions, ion fragments or ion complexes, depending on the ionization process that is used. Second, the ions are then accelerated in a vacuum and, by applying a range of different magnetic and electrical techniques, the ions can be separated into their individual masses and each mass-group sensed and identified. The basic anatomy of the mass spectrometer is shown as a block diagram in figure 1.
The sampled is first
a vacuum, usually by heat, and the molecules in the vapor can be
ionized by one of a number of different processes, which will be
discussed in due course. The charged ions then pass though an
accelerator and into a mass discriminator. Mass discrimination can
also be achieved in a number of different ways most of which will
also be discussed later in this book. Finally, the separated ions
pass into the ion sensor to be measured and their intensity recorded.
The whole system is maintained under high vacuum.
About the Author
RAYMOND PETER WILLIAM SCOTT was born on June 20 1924 in Erith, Kent, UK. He studied at the University of London, obtaining his B.Sc. degree in 1946 and his D.Sc. degree in 1960. After spending more than a decade at Benzole Producers, Ltd. Where he became head of the Physical Chemistry Laboratory, he moved to Unilever Research Laboratories as Manager of their Physical Chemistry department. In 1969 he became Director of Physical Chemistry at Hoffmann-La Roche, Nutley, NJ, U.S.A. and subsequently accepted the position of Director of the Applied Research Department at the Perkin-Elmer Corporation, Norwalk, CT, U.S.A.
In 1986 he became an independent consultant and was appointed Visiting Professor at Georgetown
University, Washington, DC, U.S.A. and at Berkbeck College of the University of London; in 1986 he retired but continues to write technical books dealing with various aspects of physical chemistry and physical chemical techniques. Dr. Scott has authored or co-authored over 200 peer reviewed scientific papers and authored, co-authored or edited over thirty books on various aspects of physical and analytical chemistry. Dr. Scott was a founding member of the British chromatography Society and received the American Chemical society Award in chromatography (1977), the M. S. Tswett chromatography Medal (1978), the Tswett chromatography Medal U.S.S.R., (1979), the A. J. P. Martin chromatography Award (1982) and the Royal Society of Chemistry Award in Analysis and Instrumentation (1988).
Dr. Scott’s activities in gas chromatography started at the inception of the technique, inventing the Heat of Combustion Detector (the precursor of the Flame Ionization Detector), pioneered work on high sensitivity detectors, high efficiency columns and presented fundamental treatments of the relationship between the theory and practice of the technique. He established the viability of the moving bed continuous preparative gas chromatography, examined both theoretically and experimentally those factors that controlled dispersion in packed beds and helped establish the gas chromatograph as a process monitoring instrument. Dr. Scott took and active part in the renaissance of liquid chromatography, was involved in the development of high performance liquid chromatography and invented the wire transport detector. He invented the liquid chromatography mass spectrometry transport interface, introduced micro-bore liquid chromatography columns and used them to provide columns of 750,000 theoretical plates and liquid chromatography separations in less than a second. Dr. Scott has always been a “hands-on” scientist with a remarkable record of accomplishments in chromatography ranging from hardware design to the development of fundamental theory. He has never shied away from questioning “conventional wisdom” and his original approach to problems has often produced significant breakthroughs.