Hybrid sector instruments

Also in general terms, the TOF part of the hybrid is used mostly for MS/MS studies in which ions produced in the magnetic sector are collided with neutral gas molecules to induce decomposition (see Chapter 23). In this mode the instrument produces more highly resolved product ion spectra than can be attained in simple magnetic-sector instruments. 

The AutoSpec -TOF hybrid mass spectrometer combines the advantages of a magnetic/electric-sector instrument with those of time-of-flight to give a versatile instrument capable of MS or MS/MS at high or low resolution. 

Scanning techniques are carried out differently with such hybrid instruments as the triple quadrupole analyzer, the Q/TOF (quadrupole and time-of-flight), and double magnetic-sector instruments. 

Mass spectrometer configuration. Multianalyzer instruments should be named for the analyzers in the sequence in which they are traversed by the ion beam, where B is a magnetic analyzer, E is an electrostatic analyzer, Q is a quadrupole analyzer, TOP is a time-of-flight analyzer, and ICR is an ion cyclotron resonance analyzer. For example BE mass spectrometer (reversed-geometry double-focusing instrument), BQ mass spectrometer (hybrid sector and quadrupole instrument), EBQ (double-focusing instrument followed by a quadrupole). 

Various tandem MS instrument configurations have been developed, e.g. sector instruments, such as CBCE, CBCECB or CECBCE, and hybrid instruments, e.g. BCECQQ (B = magnetic sector analyser, E = electrostatic analyser, C = collision cell, Q = quadrupole mass spectrometer), all with specific performance. Sector mass spectrometers have been reviewed [168],... 

With linked scan MS/MS, another analyzer is not required, but this mode gives either limited precursor selectivity with unit product-ion resolution, or unit precursor selection with poor product-ion resolution. Four-sector instruments can give very high quality data, but are costly, very space demanding, and complex. Hybrids like sector-TOF or sector-QFT are good (and cheaper) alternatives. High-energy CID MS/MS spectra are very reproducible (see Chapter 3). 

Fig. 4.15. Tandem-in-space setups for different beam instruments magnetic four-sector instrument (a), magnetic sector-quadmpole hybrid (b), triple quadmpole (c), and ReTOF (d).

Geometries composing of an oaTOF as MS2 bear the advantage that advanced TOFs offer accurate mass measurements close the the accuracy of magnetic sector instruments. Currently, QqTOF systems can be regarded as the commercially most successful hybrid. While the linear quadrupole serves as MSI in MS/MS experiments, it is operated in RF-only mode when tandem MS is not intended, because... 

The most common types of MS/MS instruments available to researchers in food chemistry include triple quadrupole mass spectrometers and ion traps. Less common but commercially produced tandem mass spectrometers include magnetic sector instruments, Fourier transform ion cyclotron resonance (FTICR) mass spectrometers, and quadrupole time-of-flight (QTOF) hybrid instruments (Table A.3A.1). Beginning in 2001, TOF-TOF tandem mass spectrometers became available from instrument manufacturers. These instruments have the potential to deliver high-resolution tandem mass spectra with high speed and should be compatible with the chip-based chromatography systems now under development. 

Bean, M. F., Carr, S. A., Thorne, G. C., Reilly, M. H. and Gaskell, S. J. Tandem mass spectrometry of peptides using hybrid and four-sector instruments a comparative study. Anal. Chem. 63 1473-1481, 1991. 

MS/MS techniques can be performed on double-focusing sector instruments as well as on quadrupole or hybrid instruments. For the purpose of this discussion will concentrate on a condensed survey of double focusing sector instruments. References that provide substantial accounts on quadrupole and hybrid instruments used for MS/MS can be found in the bibliography at the end of this chapter. 

Sector instruments and hybrid quadrupole-scctor instruments have also been u>od in a tandem manner. The first tandem mass spectrometers were sector instruments that combined an electric sector speciromc-ler with a magnetic sector spccironieier. cither in forward geometry (electric sector followed by magnetic... 

All four scan modes can be implemented with magnetic sector- and quadrupole-based true or hybrid tandem instruments. Time-of-flight (TOF) and tandem-in-time devices are also suitable for product scan experiments, but they are unable to perform the other three scans. 

Figure 3 Design of a hybrid sector-quadrupole instrument with the configuration BEqQ. FFR = field-free region.

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