Double focusing sector mass spectrometers

Table 6.29 Main characteristics of double-focusing sector mass spectrometers...

When a double-focusing sector mass spectrometer is used for GC-HRMS of the ionic species in entire spectra, the mass spectrometer has to be scanned... 

Subsequent work proved this point, while also profiting from new instrumental developments. For instance, Ulrich et al. [4] compared the performances of quadrupole-based ICP-MS and sector field (SF)-ICP-MS for the isotopic analysis of Pb in the context of two real crime scene investigations. They concluded that the latter showed better performance in terms of precision. This aspect is well known and is due to the fiat-topped (trapezoidal) peaks obtained at low mass resolution with a double-focusing SF mass spectrometer (see also Chapter 2). The authors also stressed that, although qualitative comparison of isotope ratios could be achieved without proper instrument calibration, it is better practice to measure absolute ratios by normalizing the measured raw ratios to an isotope ratio standard, preferably an isotopic reference material (IRM). 

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. 

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

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

The dwelltime of ions within the ion source is defined by the extraction voltages applied to accelerate and focus them into an ion beam and by the dimensions of that ion source. In standard El ion sources the freshly formed ions dwell about 1 ps before they are forced to leave the ionization volume by action of the accelerating potential. [41] As the ions then travel at speeds of some 10 m s they pass the mass analyzer in the order of 10-50 ps (Fig. 2.9). [9] Even though this illustration has been adapted for a double focusing magnetic sector mass spectrometer, an ion of m/z 100, and an acceleration voltage of 8 kV, the effective time scales for other types of instruments (quadrupole, time-of-flight) are very similar under their typical conditions of operation (Table 2.4). 

Combination of Magnetic and Electric Sector Fields - Double-focusing Sector Field Mass Spectrometer... 

Figure 3.5 Double-focusing sector field mass spectrometer with Nier-johnson geometry. (77. Kienitz (ed.), Massenspektrometrie (1968), Verlag Chemie, Weinheim. Reproduced by permission ofWiley-VCH)...

Figure 4.4 Schematic (a) and photograph of ion detector with extended dynamic range (b) in the double-focusing sector field mass spectrometer Element. (Reproduced by permission of Thermo Fisher Scientific, Bremen.)...

Double-focusing sector field mass spectrometer... 

An overview of commercial ICP mass spectrometers from different companies (quadrupole based ICP-MS with and without collision/reaction cell, double-focusing sector field instrumentation with single and multiple ion collectors, time-of-flight (ToF), ICP-ion trap-MS and non-commercial ICP-Fourier transform ion cyclotron resonance (FTICR) mass spectrometers is given in Figure 5.2. By using ion traps and FTICR mass spectrometers in ICP-MS isobaric interferences of atomic ions... 

Double-focusing Sector Field ICP Mass Spectrometers with Single Ion Collector (ICP-SFMS)... 

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