Hybrid tandem mass spectrometers

The TOF mass analyzer has a low duty cycle, and the combination with an ion accumulation device such as an ion trap is therefore very advantageous. It offers also MS capabilities with accurate mass measurement. In all acquisition modes, the ions are accelerated into the time of flight for mass analysis. Various other hybrid mass spectrometers with TOF have been described, including quadrupole ion trap [70] and linear ion trap [58]. High energy tandem mass spectrometry can be performed on TOF-TOF mass spectrometers [71, 72]. 

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. 

Figure 4. Effects of ion kinetic energy on the MS/MS of 5-indanol (a) MS/MS obtained on MIKES instrument with 7000 eV translational energy (b) spectrum obtained on hybrid BQ (magnet followed by quadrupole) mass spectrometer 95 eV (c) spectrum obtained with QQ (tandem quadrupole) mass spectrometer at 35 eV...

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. 

Hybrid mass spectrometer a mass spectrometer that combines analysers of different types to perform tandem mass spectrometry. 

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. 

Commercial LITs were introduced in 2002 as either a stand-alone mass spectrometer (LTQ) [318] or as part of a triple quadrupole (Q-Trap) [319] or in 2005 as part of hybrid tandem mass spectrometers (LTQ-Orbitrap and LTQ-FTICR) [88,90], Application of LTQ-FTICR for metabolism studies has been reviewed by Shipkova et al. [90], In comparison to other mass analyzer types, FTICR-based mass spectrometers are not very popular for metabolite identification studies due to availability of less expensive and more user-friendly LTQ-Orbitrap and Q-TOF-based systems. Another limitation associated with the FTICR-based hybrid mass spectrometers is the TOF effect, which results in efficient trapping of only the high-mass ions [90],... 

Glish, G.L. Burinsky, D.J. Hybrid Mass Spectrometers for Tandem Mass Spectrometry. /. Am. Soc. Mass Spectrom. 2008,19, 161-172. 

Mass spectrometers which have the capability of analysing samples by a FAB or FIB/LSIMS-source tend to be fitted with either one alternative or the other such mass spectrometers have either a magnetic sector or a quadrupole analyser (or hybrid or tandem combinations). 

Thermospray ionisation sources are usually outfitted with a quadrupole or magnetic sector mass spectrometer (including hybrids or tandem forms). Thermospray operation allows a reversed-phase solvent system, e.g. a 50 50 (v/v) water-methanol or acetonitrile mix containing 0.1 M ammonium acetate. This ensures compatibility with the universal HPLC procedures available in many industrial research laboratories. 

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],... 

It should be pointed out that FAB, MALDI, and ESI can be used to provide ions for peptide mass maps or for microsequencing and that any kind of ion analyzer can support searches based only on molecular masses. Fragment or sequence ions are provided by instruments that can both select precursor ions and record their fragmentation. Such mass spectrometers include ion traps, Fourier transform ion cyclotron resonance, tandem quadrupole, tandem magnetic sector, several configurations of time-of-flight (TOF) analyzers, and hybrid systems such as quadrupole-TOF and ion trap-TOF analyzers. 

The instrumental analysis for the identification of UV filters degradation products formed during the fungal treatment process was performed by means of HPLC coupled to tandem mass spectrometry using a hybrid quadrupole-time-of-flight mass spectrometer (HPLC-QqTOF-MS/MS). Chromatographic separation was achieved on a Hibar Purospher STAR HR R-18 ec. (50 mm x 2.0 mm, 5 pm, from Merck). In the optimized method, the mobile phase consisted of a mixture of HPLC grade water and acetonitrile, both with 0.15% formic acid. The injection volume was set to 10 pL and the mobile phase flow-rate to 0.3 mL/min. 

TOF analyzers are especially compatible with MALDI ion sources and hence are frequently coupled in aMALDI-TOF configuration. Nevertheless, many commercial mass spectrometers combine ESI with TOF with great success. For proteomics applications, the quadrupole TOF (QqTOF) hybrid instruments with their superior mass accuracy, mass range, and mass resolution are of much greater utility than simple TOF instruments.21,22 Moreover, TOF instruments feature high sensitivity because they can generate full scan data without the necessity for scanning that causes ion loss and decreased sensitivity. Linear mode TOF instruments cannot perform tandem mass spectrometry. This problem is addressed by hybrid instruments that incorporate analyzers with mass selective capability (e.g., QqTOF) in front of a TOF instrument. 

Fig. 8.1.1 Simple illustrations of a various mass spectrometers, a The triple-quadrupole tandem mass spectrometer (top panel). The middle set of quadrupoles are part of the collision cell (CC) and do not perform mass separation. MSI and MS2 indicate the first and second quadrupole mass separation devices, respectively. The bold arrow shows the path of ions, b Ion-trap mass spectrometer (middle left). The charged sections of the ion trap are not elliptical as drawn, but rather hyperbolic. The diagram is also two-dimensional, whereas the ion trap is three-dimensional. The ion path is such that ions enter the device and are trapped until a specific voltage ejects these ions, c Time of Flight mass spectrometer with a Reflectron (middle left). Ions are separated by the time it takes to pass through the instrument. The Reflectron improves/focuses the ions, d Hybrid Tandem mass spectrometer (bottom). The diagram shows that a quadrupole instrument can be combined with a different type of mass spectrometer, forming a tandem hybrid instrument...

Finally, it is important to note there are many other instruments and configurations that are often referred to as tandem mass spectrometers. There are hybrid instruments that use another form of mass separation, time-of-flight (TOF) mass spectrometry. TOF mass spectrometry separates ions based on the time it takes to... 

Instruments that incorporate two or three mass analysers in a series have been developed to study ion fragmentation. Several of the same type of mass analyser can constitute a tandem mass spectrometer, or they can be constructed using different mass analysers (hybrids). Hybrid spectrometers include the combination of magnetic sector followed by quadrupole, multiple quadrupole, quadrupole TOF, etc. In these instruments, a collision cell is placed between each analyser (Fig. 16.23). Tandem instruments have different scanning modes. 

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. 

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