Analyzer double-focus mass spectrometers

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. 

The most recent metastable defocusing technique, which is referred to as mass-analyzed ion kinetic spectroscopy (MIKES) by Beynon (77, 270, 277) and as direct analysis of daughter ions (DADI) by Maurer (278) requires the interchange of the source and collector positions in a double-focusing mass spectrometer of Nier-Johnson geometry. With... 

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. 

In 1967 Liebl reported the development of the first imaging SIMS instrument based on the principle of focused ion beam scanning [24]. This instrument, the ion microprobe mass analyzer, was produced by Applied Research Laboratories (Fig. 4.5). It used an improved hollow cathode duoplasmatron [25] ion source that eliminated filaments used in earlier sources and allowed stable operation with reactive gases. The primary ion beam was mass analyzed for beam purity and focused in a two-lens column to a spot as small as 2 pm. The secondary ions were accelerated from the sample surface into a double focusing mass spectrometer of Mattauch-Herzog geometry. Both positive and negative secondary ions were de-... 

Kemp, D. L., Cooks, R. G. and Beynon, J. H. Simulated mass-analyzed ion kinetic energy (MIKE) spectra from a conventional double focusing mass spectrometer. Int.. Mass Spectrom. Ion Phys. 21 93-101, 1976. 

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. 

Digital ion trap 64,85 Digital waveform 65 Double-focusing mass analyzers 47 Double-focusing mass spectrometers 50 Dried droplet method 39 Droplet radius 18... 

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

In this method, a sample is mounted in a vacuum chamber and bombarded with noble-gas ions at 0.5 to 3 keV. The primary ions scattered at 90° pass into an electrostatic analyzer identical in principle with those used in double-focusing mass spectrometers. By scanning the voltage to the ESA, velocity analysis is accomplished. 

Describe two methods for ionizing liquid samples for mass spectral analysis. Diagram a transmission quadrupole mass analyzer. What are the advantages and disadvantages of this mass analyzer compared with a double focus mass spectrometer ... 

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). 

Finally we should keep in mind one very important principle The mass spectrometer is a separating system itself. Thus, a double focusing mass spectrometer is a double separating system one may be used as mass separator and the other one as ion spectrometric device as it is realized in DADI/MIKE spectrometry. Trends for the improvement of this type of mass spectrometry ( MS/MS ) by the addition of a third or even a fourth analyzer are going on Many applications have shown its excellent analytical potential (see Chapter g 67.68,82.83)... 

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). 

The quadrupole analyzer has the advantages of simphcity, small size, moderate cost, and rapid scanning which make it ideal for GC-MS systems. It is restricted to about 2,000 Daltons and has low resolution when compared to double focusing mass spectrometers. 

---