Sector mass spectrometer

Figure Bl.7.4. Schematic diagram of a reverse geometry (BE) magnetic sector mass spectrometer ion source (1) focusing lens (2) magnetic sector (3) field-free region (4) beam resolving slits (5) electrostatic sector (6) electron multiplier detector (7). Second field-free region components collision cells (8) and beam deflection electrodes (9).

In the FFR of the sector mass spectrometer, the unimolecular decomposition fragments, and B, of tire mass selected metastable ion AB will, by the conservation of energy and momentum, have lower translational kinetic energy, T, than their precursor ... 

Ion Optics of Magnetic/Electric-Sector Mass Spectrometers... 

In a sector instrument, which acts as a combined mass/velocity filter, this difference in forward velocity is used to effect a separation of normal and metastable mj" ions (see Chapter 24, Ion Optics of Magnetic/Electric-Sector Mass Spectrometers ). However, as discussed above, the velocity difference is of no consequence to the quadmpole instrument, which acts only as a mass filter, so the normal and metastable mj ions formed in the first field-free region (Figure 33.1) are not differentiated. 

Peak matching can be done on quadrupole and magnetic-sector mass spectrometers, but only the latter, particularly as double-focusing instruments, have sufficiently high resolution for the technique to be useful at high mass. 

The ion optics of a magnetic-sector mass spectrometer cause the ion beam leaving the ion source to arrive at a collector after being separated into individual m/z values and focused. 

Sectors. In a sector mass spectrometer, ions are formed in an ion source that is at a potential V, usually 8 to 10 kV. Upon leaving the ion source they undergo acceleration to a velocity v, where eU = y rriv, and then enter a magnetic sector which separates the beam of ions according to their corresponding momenta. The transmission of ions through such a device is described by... 

Fig. 1. Schematic diagram of a double-focusing Nier-Johnson magnetic sector mass spectrometer where ( " ) represents paths of ions having slightly...

Fig. 6. Schematic diagram of a four-sector mass spectrometer of EBEB geometry where ESA = electrostatic analyzer (30). The flexiceU is the coUision...

Secondary Ion Mass Spectrometry Dynamic Secondary Ion Mass Spectrometry Static Secondary Ion Mass Spectrometry SIMS using a Quadruple Mass Spectrometer SIMS usii a Magnetic Sector Mass Spectrometer See Magnetic SIMS... 

Tandem quadrupole and magnetic-sector mass spectrometers as well as FT-ICR and ion trap instruments have been employed in MS/MS experiments involving precursor/product/neutral relationships. Fragmentation can be the result of a metastable decomposition or collision-induced dissociation (CID). The purpose of this type of instrumentation is to identify, qualitatively or quantitatively, specific compounds contained in complex mixtures. This method provides high sensitivity and high specificity. The instrumentation commonly applied in GC/MS is discussed under the MS/MS Instrumentation heading, which appears earlier in this chapter. 

Reactions of D with D20 and of 0 with 02, N20, and N02 have been studied with a magnetic sector mass spectrometer. Competition between electron transfer and ion-atom interchange has been observed in the production of 02 by reaction of 0 with 02, an endothermic reaction. The negative ion of the reacting neutral molecule is formed in 02, N2Of and N02 but not in D20. Rate constants have been estimated as a function of repeller potential. 

The reactions were studied with a 6-inch 60°-sector mass spectrometer. The ion source is of the Nier type (11), machined from a block of... 

The four-sector mass spectrometer is the ultimate in MS-MS instrumentation and consists of two high-resolution mass spectrometers in series. The strength of these instruments is in terms of their high-mass and high-resolution capabilities for both precursor-ion selection and product-ion analysis. Their cost, however, precludes their primary use for LC-MS and therefore they will not be considered any further here [12]. 

Four-sector mass spectrometer A mass spectrometer used for MS-MS studies consisting of two double-focusing mass spectrometers in series. 

Tri-sector mass spectrometer A mass spectrometer consisting of an electrostatic analyser (ESA), a magnetic sector and a second ESA in series. 

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