Hybrid mass spectrometer 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. 

The term Q/TOF is used to describe a type of hybrid mass spectrometer system in which a quadrupole analyzer (Q) is used in conjunction with a time-of-flight analyzer (TOP). The use of two analyzers together (hybridized) provides distinct advantages that cannot be achieved by either analyzer individually. In the Q/TOF, the quadrupole is used in one of two modes to select the ions to be examined, and the TOF analyzer measures the actual mass spectrum. Hexapole assemblies are also used to help collimate the ion beams. The hybrid orthogonal Q/TOF instrument is illustrated in Figure 23.1. 

Hybrid mass spectrometer An MS-MS instrument combining magnetic sector and quadrupole mass analysers. 

Hybrid Mass Spectrometer A tandem mass spectrometer comprised of multiple mass analyzers of different types. A Q-TOF is a hybrid, but a triple quadmpole is not. Ideally, a hybrid instrument harnesses the best features of each mass analyzer type to produce a system perhaps greater than the sum of the parts. 

Use of Mass Analyzer Scan Types Depending on the configuration of the instrument, tandem and hybrid mass spectrometers are capable of far more than simply identifying the mass of a species that emerges from the source. The following is a brief list of relevant terminology and scan types that can be useful in generating additional information to support the identification of an unknown. Note that not all scan types are feasible on all types of instrument. 

Recent innovations in mass spectrometry have provided incorporation of two, three, and four analyzers into commercially available tandem instruments. In addition, different mass analyzers may be combined to form a hybrid mass spectrometer such as the quadrupole-TOF (Q-TOF). Various types of tandem mass spectrometers include the quadruopole-TOF, time-of-flight-time-of-hight (TOF-TOF), triple-quadrupole, and Orbitrap-FTICR configurations. 

So-called hybrid mass spectrometers include a combination of two different types of mass spectrometers in a tandem arrangement. The combination of a magnetic sector mass spectrometer with a quadrupole mass spectrometer was an early instrument of this type. More popular is the combination of a quadrupole for MSI and a TOF for MS2, As with TOF/TOF, these instruments are presently used mainly for proteomics research but could eventually find applications in the clinical lab. These mstruments are unable to perform true precursor ion scans or constant neutral loss scans. Commercial examples of this type of instrument include the qTOF by Waters Micromass and the QSTAR by Apphed Biosystems/MDS Sciex. 

One of the most efficient ways to perform mass analysis with an LIT is to eject ions radially. However, this approach requires that holes be drilled into the quadrupoles and limits the possibility to operate the instrument in RF/dc mode. Hager (2002) has demonstrated the use of fringe filed effects so that ions can be mass selectively ejected in the axial direction. A hybrid mass spectrometer was developed based on a triple quadrupole platform where Q3 can be operated either in normal RF/dc mode or in the LIT ion trap mode (Fig. 8.15). 

Although there is no clear definition of a high-resolution mass spectrometer, it is generally accepted that S-MS, FT-MS, and TOF-MS devices and the related hybrid mass spectrometers are high-resolution instruments. For example, the maximum mass resolving power of a double-focusing S-MS system is roughly 60 000, and in a TOF-MS... 

For some kinds of analyses, it is convenient to have two combined mass spectrometers. This combination naturally increases costs therefore purchase of such hybrid instruments tends to require much... 

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). 

Each type of mass spectrometer has its associated advantages and disadvantages. Quadrupole-based systems offer a fairly simple ion optics design that provides a certain degree of flexibility with respect to instrument configuration. For example, quadrupole mass filters are often found in hybrid systems, that is, coupled with another surface analytical method, such as electron spectroscopy for chemical analysis or scanning Auger spectroscopy. 

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