Mass double-focussing instrument

The rate of loss of a methyl radical from the molecular ion of diethyl ether has been measured using a single-focussing mass spectrometer [42, 825]. The time resolution here was a few picoseconds. Loss of a methyl radical from the molecular ion of di-isopropyl ether has been investigated using a double-focussing instrument [743]. 

A novel HF-plasma SNMS instrument which can be combined with XPS has recently been developed [3.67]. Detection limits in the nmol/mol range have been achieved with a dedicated HF-plasma instrument attached to a double-focussing mass spectrometer [3.68]. 

A few years ago, we began a research program to develop methods of analysis which would involve the use of FAB and a high performance tandem mass spectrometer. The tandem instrument was the first triple sector mass spectrometer to be designed and built by a commercial instrument company (Kratos of Manchester, U.K.). The first mass spectrometer of the combination is a double focussing Kratos MS-50 which is coupled to a low resolution electrostatic analyzer, which serves as the second mass spectrometer U). This FAB MS-MS combination has been used to verify the structures of an unknown cyclic peptide (2), a new amino acid modified by diphtheria toxin (3), and an ornithine-containing lipid (4). A number of methods have also been worked out which rely on this instrumentation. They Include the structural determination of cyclic peptides (5), nucleosides and nucleotides (6), and unsaturated fatty acids (7) and the analysis of mixtures of both anionic (8) and cationic surfactants (9). 

Although there are many attractive features of Fourier transform mass spectrometry (FTMS), there are problems with current implementations. The FT mass spectrometer is still a relatively young instrument when compared to the double-focussing mass spectrometer, and comparisons of the spectrometers and their... 

Comparison with Sector Instruments. Modern double-focussing mass spectrometers have a long history of development, which was recently reviewed O) The instrument has evolved through a long series of complex and interweaving events beginning with the early experiments of J. J. Thomson (2) and the first mass spectrographs of... 

As already discussed above, Q-ICP-MS may still require matrix removal and preconcentration because the Q mass analyzer is unable to resolve most of the spectral interferences affecting the analytical masses of PGEs. Moreover, the detection power might be inadequate for the performance of reliable measurements in some samples. PGEs determination is hampered by mass interferences and requires high analytical selectivity and sensitivity. Double-focussing SF-ICP-MS with mass resolution capabilities higher than those afforded by Q instruments (currently up to 10,000) can properly deal with most mass interferences that have... 

In commercial instrumentation fairly low-cost quadrupole mass spectrometers and also expensive double-focussing sector field mass spectrometers are usually used (for a survey of mass spectrometers for analytical use, see Ref. [71]) and today new types of mass spectrometers such as time-of-flight mass spectrometers are being find utilized in plasma atomic spectrometry. 

Fig. 10.4 Scheme of a double-focussing magnetic sector instrument with BE configuration. Dependent on the mass-to-charge ratio the ions are distracted by the magnetic field to circular arcs with different radii. 

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