Magnetic analyzer double-focus mass spectrometers

The main advantage of the FAB technique compared to ESI and MALDI is, in fact, not the ionization method itself but the type of mass analyzer it works with. FAB ion sources are usually attached to magnetic sector, double-focusing mass spectrometers, enabling accurate mass measurements and, which is even more important, allowing the study of high-energy collision-induced dissociation (CID) reactions which provide information about the structure of the studied ion (see next section). 

Neir-Johnson geometry. An arrangement for a double-focusing mass spectrometer in which a deflection of nil radians in a radial electrostatic-field analyzer is followed by a magnetic deflection of 7t/3 radians. The electrostatic analyzer uses a symmetrical object-image arrangement, while the magnetic analyzer is used asymmetrically. 

Sputtered tons are collected and their masses analyzed in a double-focusing mass spectrometer in which Ihe velocity dispersions of Ihe magnetic anil electric sectors are matched to permit Ihe acceptance of a wide range of initial energies of the sputtered ions. No entrance slit is used and the bombarded area is stigmatically focused directly onto the resolving slit. 

BE double-focusing mass spectrometer using a magnetic sector analyzer linked to an electrostatic... 

EB double-focusing mass spectrometer using an electrostatic analyzer linked to a magnetic sector... 

Instruments using as analyzer a B,E arrangement are consequently called double-focusing mass spectrometers (see Fig. 2.5). Under these conditions, what are called first-order aberrations are overcome however, further aberrations of the ion optics are still present, due to the fringing fields present either at the magnetic or electrostatic sector levels. To reduce these undesired effects, usually electrostatic lens are placed in the field-free region of the instrument. 

Magnetic deflection mass analyzer Double focusing sector spectrometer Quadrapole mass analyzer Triple quadrapole analyzer... 

Fl/FD-MS ion sources are available from all major magnetic sector instrument manufacturers. Combination Fl/FD/El/CI sources are common. No specialized mass analyzer, such as time-of-flight (TOF-MS) or Fourier transform (FT-MS), is needed. In short, Fl-MS and FD-MS are quite compatible (and in fact are optimal) for use with the normal types of double-focusing mass spectrometers typically used for analysis of organic compounds. Since high electric fields are required in the ion source, commercial Fl/FD ion sources have not been developed for use with "low voltage" mass spectrometers (such as those with quadrupoles and ion traps). 

Calculate the radius of curvature of a [CH3 Ag] ion passing through a 0.5 Tesla magnetic field of a double-focusing mass spectrometer. The accelerating potential of the electrostatic analyzer... 

By combining a magnetic-sector mass analyzer with an electrostatic analyzer (often termed a double-sector or double-focusing mass spectrometer), a significant improvement in resolution is realized. Such a double-focusing instrument can achieve a resolution of the order of 100,OOO.The double-focusing magnetic mass analyzer utilizes two independent sectors. In addition to the... 

The calibration of the analyzer from the ions of a known compound allows the measure of the m/z ratios of the detected ions. As mentioned earlier, the ions accelerated from the source always present a certain distribution in kinetic energy at their arrival in the analyzer after collisions or Coulomb repulsions. Due to this distribution in energy, the focaUzation on the collector s slot is not perfect with ions of the same m/z ratio, which means low resolution. It is thus necessary to combine an electrostatic sector to the magnetic sector to achieve high resolution with this kind of system. The double-focusing mass spectrometer is described below. 

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