Quadrupole-linear ion trap instrumentation

Hager, J. W., and Le Blanc, J. C. (2003). High-performance liquid chromatography-tandem mass spectrometry with a new quadrupole/linear ion trap instrument. J. Chromatogr. A 1020 3-9. 

Li, A. C., Gohdes, M. A., and Shou, W. Z. (2007). N-in-one strategy for metabolite identification using a liquid chromatography/hybrid triple quadrupole linear ion trap instrument using multiple dependent product ion scans triggered with full mass scan. Rapid Commun. Mass Spectrom. 21 1421-1430. 

Many similar applications of quadrupole linear ion trap instruments have been reported [320-322,329,330], As discussed above, the Q-Trap is a triple quadrupole mass spectrometer capable of performing QMF type and 2D ion trapping experiments. This mass spectrometer can be operated exclusively in the QMF mode, as with a conventional QMF, or it can be operated exclusively in the ion trapping mode similar to a conventional 2D ion trap mass spectrometer. Advantages of using a Q-Trap mass spectrometer over a conventional QMF mass spectrometer come into play when one is attempting to perform both quantitative and qualitative metabolite detection/identification experiments from a single injection rather than separate... 

Since this original description of the ETD/CID MS/MS scan type (ETcaD), it has been implemented on commercial instruments, applied toward biologically-relevant samples, and expanded upon [28,85,91,92]. For example, Han et al. [92] coupled ETD with beam-type CID on their QTRAP hybrid triple quadrupole/linear ion trap instrument (Figure 3.4). An advantage of both this implementation, and beam-type CID in general, is that the spectra do not suffer from the low mass cut-off that is... 

FIGURE 3.4 Schematic diagram of the QTRAP hybrid triple quadrupole/linear ion trap instrument that has been modified to conduct ion/ion reactions in Q2. (Reproduced from Han, H.L. Xia, Y. McLuckey, S.A., Rapid Commun. Mass Spectrom. 2007, 21, 1567-1573. With permission from John Wiley Sons, Inc.)... 

Electron-Transfer Dissociation A new technique, electron-transfer dissociation (ETD), has been introduced for fragmentation of multiply charged peptide ions [29-31], The process is similar to BCD but uses an ion-ion reaction to transfer an electron to the peptide ion. Anthracene anions generated in a Cl source are employed as electron donors. ETD methodology has been adapted in a quadrupole linear ion-trap instrument. Analogous to the ECD process, the transfer of an electron induces fragmentation in the peptide backbone to produce sequence-specific c- and z -type ions. 

Li AC, Gohdes MA, Shou WZ. iV-in-one strategy for metabolite identification using a liquid chromatography/hybrid triple quadrupole linear ion trap instrument using... 

Mass spectrometric analysis was performed with a hybrid triple quadrupole/ linear ion trap Applied Biosystem MSD Sciex 4000QTRAP (Applied Biosystems, Foster City, USA) instrument equipped with a Turbospray ESI interface. For target quantitative analyses, data acquisition was performed in SRM, recording the transitions between the precursor ion and the two most abundant fragment ions. The developed instrumental method display excellent LODs in SRM mode between 0.5 and 1.2 pg (Table 2). 

A new generation of linear ion trap mass spectrometers has been developed and exhibits increased performance compared to traditional three-dimensional (3D) ion traps (Hopfgartner et al., 2003 Douglas et al., 2005). A further evolution of the triple-quadrupole family and ion trap class of instruments is the production of the hybrid triple-quadrupole/linear ion trap (QQQ/LIT) platform. Hybrid instruments of this nature allow for operation in space and not just in time when performing MS/MS analysis. This feature allows for increased performance compared to classical ion traps. A powerful combination possible on a hybrid LIT/QQQ instrument is the ability to use highly sensitive and selective precursor ion, constant neutral loss, and multi-MRM as a survey scan for dependent LIT MS/MS. Compared to a simple MS experiment, these comprehensive triple-quadrupole and LIT modes can be more complex to setup. 

S uzuki et al. report a hybrid triple quadrupole/linear ion trap MS/MS technique. The triple quad-rupole-linear ion trap LC/MS combines the scan speed and sensitivity of ion trap MS while retaining the selective scanning modes of triple quadrupole MS. The ability to perform both types of MS on a single instrument reduces the time required for analysis while eliminating the chance of errors due to analyzing different samples in multiple MS runs. The method, coupled with LC separation, was demonstrated to be usefuUy applied to the structure elucidation of YTX analogues. ... 

A mass analyzer separates and mass-analyzes the ionic species. Magnetic and/or electric fields are used in mass analyzers to control the motion of ions. A magnetic sector, quadrupole, time-of-fiight, quadrupole ion trap, quadrupole linear ion trap, orbitrap, and Fourier transform ion cyclotron resonance instrument are the most common forms of mass analyzers currently in use (discussed in Chapter 3). 

Linear Ion Trap-oa-TOF Instrument A useful alternative design combines a quadrupole linear ion trap (LIT) with an oa-TOF mass analyzer [62]. This instrument consists of a short rf quadrupole ion guide, a quadrupole mass filter that operates in the rf-only mode, and an oa-TOF mass analyzer. The quadrupole mass filter is operated as an LIT to serve as an ion-accumulation and precursor-ion selection device. The mass-selected precursor is activated via a resonant excitation mode in the LIT, while the TOF instrument provides high-speed mass analysis of the resulting product ions. MS experiments have also been demonstrated with this hybrid system. A combination of QIT with an oa-TOF mass analyzer has also proven to be an effective tandem MS system [63,64]. The QIT performs tasks similar to those performed by an LIT in the LIT-oa-TOF design (i.e., its functions are ion accumulation, mass separation, and ion activation. 

In 2002, two linear ion traps were reported they had the basic structure of a quadrupole mass filter. The first linear ion trap instrument was described by J.W. Hager of MDS SCIEX and a second linear ion trap instrument was described by J.C. Schwartz, M.W. Senko, and J.E.P. Syka of Thermo Einnigan. Both instruments employ mass-selective ion ejection. Axial ion ejection is employed in the SCIEX instrument while in the Thermo Einnigan instrument ion ejection occurs radially. In addition, ion trapping in the SCIEX instrument can occur either in a pressurized collision cell region or in a low-pressure quadrupole rod array downstream of the collision cell. 

Currently, four types of mass analyzers are commonly utilized for qualitative and quantitative DMPK applications triple quadrupole, ion trap and linear ion trap, triple quadrupole linear ion trap, and high-resolution mass spectrometers (Table 6.1) [13-15]. Scan functions, major applications, and significant limitations of these instruments are included in Table 6.1. 

The use of analyzers like quadrupole (Q), time of flight (TOP) and ion trap (IT) evolved towards combinations of them to achieve tandem instruments, as triple quadrupole (QqQ), hybrid quadrupole linear ion trap (QqLIT) and quadrupole time of flight (QqTOF). In the last few years due to the improved characteristics of sensitivity and selectivity and to the need to collect a great amount of information for identification and elucidation pnrposes, we assisted to a rapid evolution of different analyzer designs. 

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