Orbitrap Fourier transform mass

Technological advances of ion-trap mass spectrometers are the ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and the recently released technique, the Orbitrap Fourier transform mass spectrometry (Hu et al., 2005), which enable the determination of molecular formulae with a high mass resolution and mass accuracy in mixtures. Today these ion-trap mass spectrometers are most frequently coupled with atmospheric pressure ionization (API) techniques such as electrospray ionization (ESI) (e.g., Fievre et al., 1997 Qian et al., 2001 Kujawinski et al., 2002 Llewelyn et al., 2002 Stenson et al., 2002,2003 Fard et al., 2003) or matrix-assisted laser desorption/ionization (MALDI) (e.g., Solouki et al.,... 

Kamleh A, et al. Metabolomic profiling using Orbitrap Fourier transform mass spectrometry with hydrophilic interaction chromatography A method with wide applicability to analysis of biomolecules. Rapid Commun Mass Spectrom 2008 22 1912-1918. 

Along with advances in various ionization sources, significant improvements have been made in the area of mass analyzers. Mass analyzers can be differentiated based on several attributes such as scan speed, duty cycle, mass resolution, mass range, and cost [126], The most common analyzers used for metabonomics analyses include the quadrupole and TOF-based analyzers [125-127], Some other analyzers that have been reported for use in MS-based metabonomics analyses are the ion traps, Orbitraps, and Fourier transform mass spectrometers [128,129],... 

These developments [together with the availability of high-performance instruments, e.g., Fourier transform-mass spectrometry (FT-MS) and Orbitrap] make possible the application of MS in many different fields. The problem is to individualize the best instrumental choices and the related parameterization to obtain the analytically more valid results, which allows to propose new, highly specific analytical methods. 

Fourier Transform Mass Spectrometer (FTMS) Fourier transformation (FT) of time-dependent image from the detector to m/z intensity is utilized for two types of mass spectrometers ion cyclotron resonance (ICR) and Orbitrap. FTICR mass spectrometers operate based on the ion cyclotron resonance principle ions in a magnetic field (B) move in circular orbits at frequencies (ft>c) characteristic of their m/z values as shown below (Marshall et al., 1998,2002) ... 

Full Fourier transform mass spectrometric (FTMS) data are acquired at various resolving power settings, from 7,500 to 100,000 w/z400 seel and 8 for Orbitrap analyzer operation details). FTMS acquisitions are done using a 30 xm raster. 

The second set of instruments concerns the high resolution (HR) instruments such as TOP, orbitrap, Fourier transform ion cyclotron resonance (FT-ICR), from which accurate full-scan MS data can be obtained. Accurate mass data are essential for the identification of the appropriate elemental composition and the elucidation of unknown chanical structures can be obtained by using powerful software to mine the recorded chromatogram. 

LC-TOF MS offers fuU-scan high sensitivity, high mass accuracy close to that provided by high-resolution Fourier-transform mass spectrometry (FT-MS) instruments (orbitrap and FT-ICR-MS). 

Once ions are produced, they are typically directed into a mass analyzer, where the ions are separated by their mass-charge ratios and detected. The types of mass analyzers vary widely.By far, the most common is the time-of-flight mass analyzer due to its simplicity and the pulsed nature of ion extraction from the ion source, which makes it especially compatible with pulsed laser excitation, but laser desorption/ionization sources have been coupled to quadrupoles, electromagnetic sector instruments, orthogonal time-of-flight mass spectrometers, quadmpole ion traps, Fourier transform mass spectrometers, and even the recently introduced Orbitrap. Detailed discussion of these mass analyzers is beyond the scope of this chapter but is not out of the scope of other chapters in this volume and elsewhere. However, laser desorption ion sources produce ions with a particular momentum and temperamre, and great care must be taken in coupling these ion sources to the mass spectrometers so that the ions momentum and temperature parameters are compatible with the instrument at hand. 

Ion detection is carried out using image current detection with subsequent Fourier transform of the time-domain signal in the same way as for the Fourier transform ion cyclotron resonance (FTICR) analyzer (see Section 2.2.6). Because frequency can be measured very precisely, high m/z separation can be attained. Here, the axial frequency is measured, since it is independent to the first order on energy and spatial spread of the ions. Since the orbitrap, contrary to the other mass analyzers described, is a recent invention, not many variations of the instrument exist. Apart from Thermo Fischer Scientific s commercial instrument, there is the earlier setup described in References 245 to 247. 

Capillary electrophoresis (CE) either coupled to MS or to laser-induced fluorescence (LIF) is less often used in metabolomics approaches. This method is faster than the others and needs a smaller sample size, thereby making it especially interesting for single cell analysis [215] The most sensitive mass spectrometers are the Orbitrap and Fourier transform ion cyclotron resonance (FT-ICR) MS [213]. These machines determine the mass-to-charge ratio of a metabolite so accurate that its empirical formula can be predicted, making them the techniques of choice for the identification of unknown peaks. 

With time of flight instruments, a mass accuracy better than 5 ppm can be achieved, while with Fourier transform ion cyclotron resonance or orbitrap mass spectrometers mass accuracies better than 1 ppm have been reported. It is obvious that, for good mass accuracies, the peaks must be baseline resolved and resolution plays an essential role. For the present example, a mass resolving power of 5000 seems to be quite acceptable. In the case of the [M+H]+ + 1 isotope peak, the situation becomes somewhat more complex for molecules containing nitrogen, sulfur or carbon. Figure 1.5 D illustrates at a mass resolving power of 500000 the contribution of... 

Orbitrap The newest of the major mass analyzers, the Orbitrap is a hybrid MS consisting of a LIT mass analyzer, or transmission quadmpoles connected to the high-resolution Orbitrap mass analyzer. The Orbitrap utilizes electrical fields between sections of a roughly egg-shaped outer electrode and an inner (spindle) electrode (Chapter 5). Ions orbit between the inner and outer electrodes and their oscillation is recorded on detector plates (Hardman and Makarov, 2003 Hu et al., 2005). As with the FTICR, fast Fourier transform of the raw data is used to convert the data for mass analysis, making the Orbitrap the second major type of FTMS instrument. The resolving power of the Orbitrap is intermediate... 

Nevertheless, even with accurate mass measurement by Q-TOF, LTQ-Orbitrap, or LTQ-Fourier transform ion cyclotron resonance (LTQ-FTICR) MS, it is not always possible to fully characterize certain metabolites based solely on mass spectrometric... 

However, most modem highly accurate time-of-flight (TOF), Fourier-transform ion cyclotron resonance (FT-ICR) and Orbitrap mass analysers [107] have not been reported for TA analysis so far and are thus not discussed in this chapter. 

The orbitrap is an electrostatic ion trap that uses the Fourier transform to obtain mass spectra. This analyser is based on a completely new concept, proposed by Makarov and described in patents in 1996 [26] and 2004 [27], and in Analytical Chemistry in 2000 [28], A third patent describes a complete instrument including an atmospheric pressure source [29], Another article was also published with Cooks in 2005 [30]. The first commercial instrument was introduced on the market by the Thermo Electron Corporation in June 2005. 

Orbitrap analyser a mass analyser that store the ions in a quadro-logarithmic field. The ions are selectively detected according to their m/z values using their induced current. The treatment of this current by a Fourier transform yields their mass-to-charge ratios. It is an analyser with very high-resolution capacity. 

ToF analyzers as well as hybrid instruments that combine two or more mass-resolving components, such as quadrupole-ToF (Q-ToF), ion-mobility ToF, and ion-trap-ToF, as well as the high-resolving Fourier transform (FT) analyzer Orbitrap and ion cyclotron resonance (ICR). For targeted analysis, a multiple-reaction monitoring instrument based on triple-quadrupole technologies (QQQ) has provided unrivaled sensitivity for MSI of pharmaceuticals, yet its targeted nature renders it unsuitable for discovery-based research. 

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