Mass spectrometers LTQ-Orbitrap

Figure 5.6. Schematic of a hybrid LTQ-Orbitrap mass spectrometer (a) transfer octapole (b) curved rf-only quadmpole (C-trap) (c) gate electrode (d) trap electrode (e) ion optics (f) inner orbitrap electrode (g) outer orbitrap electrodes (Makarov et at., 2006a).

Linear Ion Trap-Orbitrap Mass Spectrometer A recent addition to the family of hybrid tandem mass spectrometers is a linear ion trap (LTQ)-orbitrap mass spectrometer [69,70]. Conceptually, this instrument is similar to the LTQ/FT-ICR tandem mass spectrometer discussed above but uses an orbitrap in place of a Penning trap, thus avoiding the complexity and cost of a superconducting magnet. The working principle of an orbitrap was described in Section 3.9 [71,72]. A schematic diagram of the LTQ/orbitrap mass spectrometer is shown in Figure 4.14. This hybrid tandem mass spectrometer consists of an... 

One of the latest mass analyzer is the linear-trap quadrupole (LTQ) Orbitrap mass spectrometer. In this, the commercial LTQ is coupled with an ion trap, developed by Makarov [73, 74]. Due to the resolving power (between 70000 and 800000) and the high mass accuracy (2-5 ppm), Orbitrap mass analyzers, for example, cab be used for the identification of peptides in protein analysis or for metabolomic studies. In addition, the selectivity of MS/MS experiments can be greatly improved. However, the coupling is not useful with UHPLC for rapid chromatographic pre-separation, as the data acquisition rate is too low for a reproducible integration of the narrow signals produced with UHPLC. 

Y. Xu, J.-F. Heilier, G. Madallnski, E. Genin, E. Ezan, J.-C. Tabet, and C. ]unot. Evaluation of accurate mass and relative isotopic abundance measurements in the LTQ-Orbitrap mass spectrometer for further metabolomics database building. Anal. Chem., 82 5490-5501,2010. 

Only a few applications of orbital-trap (orbitrap) high-resolution mass spectrometers have been reported for STA or GUS so far. For the detection of 29 doping agents, an LTQ-orbitrap mass spectrometer equipped with an APCI ion source was used with insource CID and acquisition in the positive ionization scan mode from 100 to 500 Da (35). The mass resolution of60,000 fiill width at half maximum (FWHM) ensured a precision better than 2 ppm (using external calibration), while the limit of detection was better... 

Schuhmann, K., Herzog, R., Schwudke, D., Metelmann-Strupat, W., Bomstein, S.R. and Shevchenko, A. (2011) Bottom-up shotgun lipidomics by higher energy colhsional dissociation on LTQ Orbitrap mass spectrometers. Anal. Chem. 83, 5480—5487. 

Fig. 4.66. The Thermo Scientific LTQ orbitrap mass spectrometer. The front end up to the LIT is identical to the LTQ instrument introduced in Chap. 4.5.3 and Rg. 4.41. Ions axially ejected from the LIT are entering (a) a transfer octopole to (b) a curved RF-only quadm-pole known as C-trap, from where they are injected via (c) gate electrode, (d) trap electrode, and (e) ion optics into the orbitrap comprising (f) the inner electrode and (g) outer electrodes for detection. Note that there are four ports for differential pumping along the LTQ section and another three sideways to reduce the pressure from the C-trap to the orbitrap. Adapted from Ref. [208] with permission. American Chemical Society, 2006.

FIGURE 13.3 Instrument schematics for (a), Waters Synapt QTOF ( Waters), (b) Thermo Finnigan LTQ-Orbitrap, and (c) Thermo Finnegan LTQ FTICR mass spectrometers ( Thermo Finnegan). 

Makarov, A, E. Denisov, O. Lange, and S. Horning. 2006a. Dynamic range of mass accuracy in LTQ Orbitrap hybrid mass spectrometer. J. Am. Soc. Mass Spectrom. 17 977-982. Makarov, A., E. Denisov, A. Kholomeev, W. Balschun, O. Lange, K. Strupat, and S. Homing 2006b. Performance evaluation of a hybrid linear ion trap/orbitrap mass spectrometer. Anal. Chem. 78 2113-2120. 

A. Makarov, E. Denisov, O. Lange, and S. Homing. Dynamic Range of Mass Accuracy in LTQ Orbitrap Hybrid Mass Spectrometer. J. Am. Soc. Mass Spectrom., 17(2006) 977-982. 

The sensitivity of the LTQ-Orbitrap is demonstrated using a mixture of synthetic standards of buspirone metabolites spiked into a rat plasma extract. The samples were analyzed with a standard 4.6-mm HPLC column. LC-MS/MS chromatograms for the five-component mixture obtained using the Orbitrap and the LTQ mass spectrometers are compared in Figs 5.8a and h. Also shown are MS/MS (m/z 402) spectra of the oxa-buspirone metabolite (R, = 7.4 min) at 10 pg on column in the Orbitrap (Fig. 5.8c) and LTQ (Fig. 5.8e). As discussed above, the MS/MS fragmentation spectra, obtained in the Orbitrap (Figs 5.8c and d), are very similar to those from the LTQ (Fig. 5.8e), and even at such low concentrations excellent mass accuracies are maintained. 

Chen, G., Khusid, A., Daaro, I., Irish, P., and Pramanik, B. N. (2007). Structural identification of trace level enol tautomer impurity by on-line hydrogen/deuterium exchange HR-LC/MS in a LTQ-Orbitrap hybrid mass spectrometer. J. Mass Spectrom. 42 967-970. 

Makarov, A., Denisov, E., Lange, O., and Homing, S. (2006b). Dynamic range of mass accuracy in LTQ Orbitrap hybrid mass spectrometer. J. Am. Soc. Mass Spectrom. 17 977-982. 

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],... 

Lim, H.K. et al., Metabolite identification by data-dependent accurate mass spectromet-ric analysis at resolving power of 60,000 in external calibration mode using an LTQ/ Orbitrap, Rapid Commun. Mass Spectrom., 21(12), 1821, 2007. 

Chen, G. et al., Structural characterization of in vitro rat liver microsomal metabolites of antihistamine desloratadine using LTQ-Orbitrap hybrid mass spectrometer in combination with online hydrogen/deuterium exchange HR-LC/MS, J. Mass Spectrom., 44(2), 203, 2009. 

Figure 4.14. Schematic diagram of the LTQ/orbitrap hybrid tandem mass spectrometer a, transfer octopole b, C-trap c, front gate electrode d, rear trap electrode e, ion optics f, inner orbitrap electrode g, outer orbitrap electrode. (Reproduced from ref. 69 by permission of the American Chemical Society, Washington, DC, copyright 2006.)...

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