Sector analyzer

The double-focusing combination of electrostatic- and magnetic-sector analyzers allows the inherent energy spread of the beam to be compensated for by design and ensures that there is no spread in the beam at the collector. 

This last m/z value is easy to measure accurately, and, if its relationship to the true mass is known (n = 10), then the true mass can be measured very accurately. The multicharged ions have typical m/z values of <3000 Da, which means that conventional quadrupole or magnetic-sector analyzers can be used for mass measurement. Actually, the spectrum consists of a series of multicharged protonated molecular ions [M + nWY for each component present in the sample. Each ion in the series differs by plus and minus one charge from adjacent ions ([M + uH] + n -an integer series for example, 1, 2, 3,. .., etc.). Mathematical transformation of the spectrum produces a true molecular mass profile of the sample (Figure 40.5). 

Momentum spectrum. A spectrum obtained when a beam of ions is separated according to the momentum-to-charge (m/z) ratios of the ionic species present. A magnetic-sector analyzer achieves separation of the various ionic species in this way. If the ion beam is homogeneous in translational energy, as is the case with sector instruments, separation according to the m/z ratios is also achieved. 

The obtained results allow us to advance with the basic assumption the north sector, subject to anthropogenic influence, it showed a carbon stock 23% lower than the south sector, which had less accessibility and a better state of conservation (Table 4). These differences were statistically significant (H = 11.20, p < 0.001) only for the AGB stratum, but not for the other strata studied nor for the total carbon stock. Under similar conditions of climate, soil, geomorphology, altitude, and latitude, the human influence could explain these differences, as the AGB stratum is the easiest to appropriate by humans [10,17,19, 21]. The AGB make the largest contribution in both sectors to the carbon stock (53, 55%), followed by SOC (28-31%) and finally BGB (8-10%) depending on the sector analyzed (Figure 3). 

TI is a very precise and accurate method in stable isotope ratio measurements and quantification of inorganic elements, for example, by isotope dilution mass spectrometry [8]. Because TI is a continuous ion source, it could be coupled to any analyzer that is suitable for such sources. However, because the strength of TI lies in the quantitative precision and accuracy, sector analyzers are preferred to ensure maximum quality. 

Like sector analyzers, quadrupole analyzers are well suited for continuous ion sources such as ESI, but are not well-suited for pulsed ionization methods. Quadmpole mass spectrometers are generally substantially cheaper and smaller than sector instruments and Qq-TOFs. They are very often used in combination with GC and LC, and single or triple quadmpole mass filters are very common benchtop instruments for routine measurements. 

Focal plane detectors are used primarily to detect ions separated in space by, for example, magnetic sector analyzers (see Section 2.2.2). The objective of an ideal focal plane detector is to simultaneously record the location of every ion in the spectrum. In many ways the photoplate (see Section 2.3.1) is the original focal plane detector, but it has today been more or less replaced with designs that rely on EM detectors (see Section 2.3.3). A common arrangement is to allow the spatially disperse ion beams simultaneously to impinge on an MCP (see Section 2.3.3.2). The secondary electrons generated by the ion impacts then strike a one- or two-dimensional array of metal strips and the current from the individual electrodes is recorded. A tutorial on the fundamentals of focal plane detectors is found in Reference 283. Reference 284 provides a relatively recent review of MS detector-array technology. 

Fig. 8.8. FD probe inserted into the vacuum lock. FD probes are generally inserted in axial position to leave the vacuum lock of the DIP free for FI use. The emitter wire is now oriented vertically to comply with the beam geometry of the magnetic sector analyzer.

Mass range is the m/z range of the mass analyzer. For example, quadrupole analyzers typically only scan up to m/z 3000, magnetic sector analyzers can go to m/z 10 000, and time-of-flight analyzers have virtually unlimited m/z. 

Fig. 14. Schematic diagram for XPS measurements with a spherical sector analyzer and electrostatic lenses.

We tested whether it was possible to make long term projections of chemical prices from an understanding of Hkely future reinvestment economics. Historical prices were compared with actual reinvestment economics for leader players in 10 commodity sectors in Western Europe over 20 years from 1980 - a period which contained at least two cycles. The sectors analyzed included major intermediates such as styrene and terephthalic acid, plus polyolefines and polystyrene. 

Molecules that are ionized by electron impact in the ion source are accelerated, sent through a conventional 90° magnetic sector analyzer, postaccelerated by a few thousand volts, and arrive at the electron multiplier detector. The output of the electron multiplier detector consists of pulses of about lO- coulomb per ion. The pulses are amplified and sent through a gated amplifier and an electronic switch which is synchronized with the beam chopper so that one of the ion counters records ions only when the beam chopper is open, the other only when the beam chopper is closed. The difference between the two ion counts represents the ion intensity contributed by the molecular beam, while the square root of the sum of the two ion counts is approximately equal to the standard deviation of the measurement and serves as a useful indicator of the quality of the data being obtained. 

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

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