Mass spectrometer magnetic

FIGURE 1 A schematic drawing of a large magnet mass spectrometer. 

R. S. Annan, H. J. Kochling, J. A. Hill, and K. Biemann. Matrix-Assisted Laser Desorption Using a Fast-Atom Bombardment Ion Source and a Magnetic Mass Spectrometer. Rapid Commun. Mass Spectrom., 6(1992) 298-302. 

Mouget, Y. Bertrand, M.J. Graphical Method for Artefact Peak Interpretation, and Methods for Their Rejection, Using Double and Triple Sector Magnetic Mass Spectrometers. Rapid Commun. Mass Spectrom. 1995,9,387-396. 

A schematic view of a magnetic mass spectrometer is shown in Figure 9.1. 

In the geometric separation method, ions having different m/e ratios are separated according to their geometric position at the collecting spot. The magnetic mass analyzer, the quadrupole mass analyzer, and the ion trap are based on these principles of operation. The magnetic mass spectrometer will not be discussed in this chapter as it has not been used for the detection of explosives. 

B = magnetic sector E = electric sector. Six types of magnetic mass spectrometers are displayed. Instruments 4, 5 and 6, with double focusing, are most frequently used. Instrument 4 is dispersive, while 5 and 6 are scanning types. The photographic plate in 4 can be replaced by an array detector for limited mass ranges. Reproduced from Finnigan MAT documentation, with permission. 

We had previously used this technique for studying several alkali halides, including Nal, (23) the cesium halides (2A) and the rubidium halides. (25) The apparatus consisted of a one-meter normal incidence monochromator and a magnetic mass spectrometer. In these earlier studies, ionic species attributable to dimer and monomer were studied, but the intensity of trimer was too weak for measurement. With our more recent interest in trimer, we once again turned to the lithium halides. This time, our apparatus consisted of a three-meter normal incidence monochromator and a quadrupole mass spectrometer. (7 )... 

An example of a similar spectrometer is the one used by Champion et al.9 Primary ions were produced by electron bombardment, accelerated and mass analysed by a 60°, 13-3 cm magnetic mass spectrometer. The ions were then retarded to the desired energy and energy selected by a 127° electrostatic cylindrical velocity selector. The energy resolution was 5 %. The beam half angle is reported to be 18°. The ions then entered a reaction chamber at a pressure of about 10 4torr. The chamber had an exit slit which could be rotated with the detecting system which consisted of another 127° velocity selector, a quadrupole mass spectrometer and an electron multiplier. 

Fig. 12. Sdiematic drawing of an FD ion source for fast and simple analysis of trace metals in a single focusing magnetic mass spectrometer ...

Probably the first pyrolysis-mass spectrometer was described by Meuzelaar and Kistemaker. This instrument was based on a Riber quadrupole mass spectrometer and used the Curie-point pyrolysis method first described by Giacobbo and Simon. This development eventually produced two commercial instruments — the Extra-nuclear 5000 (Extranuclear Laboratories, Pittsburgh, PA), effectively a copy of the FOM machine, and the Pyromass 8-80 (VG Gas Analysis, Middlewich, England), based on the same principles but using a small magnetic mass spectrometer. 

An alternative method of filtering is based on the use of a magnetic field. Magnetic mass spectrometers were developed and improved by the fathers of mass spectrometry, Thompson, Aston, and Bainbridge, in the early part of the twentieth century. An ion with velocity v travelling in a perpendicular magnetic field of flux density B will follow a circular trajectory of radius r. 

FIG. 3. Interactive data system for magnetic mass spectrometer (Courtesy of Varian/MA.T, Sprinfield, New Jersey). 

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