Single-focusing magnetic sector

Example The metastable decay of the o-nitrophenol molecular ion, m/z 139, by loss of NO to yield the [M-NO] ion, m/z 109, has been studied on a single-focusing magnetic sector instrument (Fig. 2.11. [45] The mass spectrum shows a... 

The ions formed are extracted by the extraction lens, EL, perpendicular to the electron beam. Due to the low energy spread of ions formed in an electron ionization source (< 1 eV) one single-focusing magnetic sector field mass spectrometer or quadrupole analyzer is sufficient for... 

Figure 2. Schematic of a nonfocusing LMI source attached to the ion source of a single-focusing magnetic-sector mass spectrometer.

Samples weighing 2-5 mg are then dissolved in 5-molar nitric acid. The strontium fraction is purified using ion-specific resin and eluted with nitric acid followed by water. This solution is loaded onto a titanium filament for placement in the instrument (Fig. 4.20). Isotopic compositions are obtained on the strontium fraction thermal ionization mass spectrometer (TIMS). This is a single focusing, magnetic sector instrument equipped with multiple Faraday collectors. Strontium is placed on a thin filament and measured. Sr/ Sr ratios are corrected for mass fractionation using an exponential mass fractionation law. Sr/ Sr ratios are reported relative to a value of 0.710250 for the NIST 987 standard (e.g., if the Sr/ Sr ratios for the standards analyzed with the samples average 0.710260, a value of 0.000010 is subtracted from the ratio for each sample). 

Different mass spectrometer-Knudsen cell systems are used at various laboratories. Single-focusing magnetic sector field or quadrupole mass spectrometers are used in most cases for the analysis of the molecular beam. 

Half a century ago a mass spectrometer was a single focusing magnetic sector instrument its console contained a clock to facilitate reproducible measurements, since it was mainly used for analyses of hydrocarbon mixtures. Very often an analog computer was associated with the instrument in order to permit the solution of the linear equations needed to... 

Special mass spectrometry systems are built for isotope ratio measurements. Most isotope ratio mass spectrometers consist of a single-focusing magnetic sector instrument and a multiple Faraday cup detection system. Because the Faraday cup exhibits a stable response, it is an ideal detector for isotope ratio measurements. Simultaneous collection of relevant ion beams from all isotopes provides high-precision isotopic measurements. A three-Faraday cup detection system is shown in Figure 7.9. The multicup assembly is placed at the focal plane of the mass analyzer and can be used for the simultaneous detection of each isotopic form of the analyte species (e.g., m/z 44, 45, and 46 from CO2). Commercial instruments with up to nine collectors are available. 

ESA s Giotto mission to Comet P/Halley in 1986 carried three single-focusing magnetic sector mass spectrome-... 

Figure 22 EI( +) mass spectra obtained from aS-OH-Dj as (a) per-trimethylsilyl (TMS) ether on a single focusing magnetic sector GC-MS (LKB 2091) (b) per-TMS ether on a benchtop quadrupole system tuned to high mass and (c) mixed TMS ether/t-butyldimeth-ylsUyl ether on a magnetic sector GC-MS (LKB 2091). (From Ref. 208.)...

Due to the low spatial and energetic spread of ions from TI, the method can be combined with single-focusing magnetic sector mass analyzers or quadrupoles [35], Nonetheless, TI ion sources require dedicated instrumentation, frequently equipped with multicollector (MC) systems to insure the highest accuray for the isotope ratios measured (Chaps. 3.3.2 and 7.2 in [3]). 

The mass dispersion coefficient (D ) of a single focusing magnetic sector is proportional to the radius of curvature (r j ) of the ion beam trajectory in the magnetic field. The spatial separation (y) of two similar masses with mean mass (m) and mass difference (Am) is related to the mass dispersion coefficient by ... 

Figure 1 Single-focusing magnetic sector, with focusing inFigure 2 Single-focusing magnetic sector, with stigmatic direction only. focusing in V and Z directions.

Figure 1.4. Single-focusing, magnetic-sector mass spectrometer.

The mass to charge ratio for a single focusing magnetic sector is given by ... 

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