FT-Orbitrap

FT-Orbitrap Metabolites, lipids, peptides Very high mass resolution accurate mass leading MS/MS capabilities Imaging sources provided by third-party companies... 

For general purpose instruments (scenario 2), the most important parameters are resolution and accurate mass measurement for the identification and characterization of unknowns. Typical are MS/MS systems based on TOE or FT (orbitrap or ICR). The major categories here are TOF/TOF, QTOF, LT-TOF, LT-orbitrap, and LT-FT-ICR. For analytes of >1 kDa, TOF/TOF systems in combination with MALDI sources are straightforward and should be evaluated where multiple users are involved. QTOF, LT-TOF, and LT-orbitrap are all suited to LC operation at regular or nanoflow rates. The resolution of orbitraps is much higher (250,000) than that of TOF instruments (20,000 to 60,000), although available resolution on the former is subject to duty cycle limitations. Table 3.13 lists representative examples of the types of instruments one might consider for common applications. 

The resolution of a mass analyzer is typieally quoted as the unitiess quantity m/Am, where Am is the mass difference between two adjacent peaks that are just resolved and m is the mass of the first peak in the spectrum. TOF-MS can achieve a resolution of up to 50000 (meaning that it can resolve peaks occurring at, e.g., 500.00 and 500.01 atomic mass units (Da), or 50.000 and 50.001 Da], FT-orbitrap up to 500000, and FTICR-MS as much as 500000-1000000. In fact, the latter two mass analyzers offer such high mass accuracy that experiments can even account for the masses of individual electrons (around 0.00054 Da). 

Mass Spectrometric Conditions In the present work, a linear ion trap—FT Orbitrap mass spectrometer (Thermo Electron, Bremen, Germarty) was used. The ion trap part of this system was equipped with an ion max electrospray ionization (ESI) probe that can be apphed in the positive- and negative-ion mode for the compormds investigated. The present chapter only presents results of the positive-ion mode. 

Hogenboom, A. C., J. A. van Leerdam, and P. de Voogt. 2009. Accurate mass screening and identification of emerging contaminants in environmental samples by liquid chromatography-LTQ FT Orbitrap ms. J. Chromatogr. A 1216 510-519. 

FT-ICR and the Orbitrap belong to this group. In these analyzers the m/z values of the ions are not directly measured, but they are obtained by Fourier transform treatment of the signal (Figure 2.12). 

The Orbitrap allows very high resolution to be achieved (the resolving power in commercial instruments is 100000, rivalling that of FT-ICR instruments) and routine mass measurement accuracies less than 2 ppm. It finds applications in many fields, such as biology, proteomics, food chemistry and cultural heritage. 

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. 

The particularity of the LIT-orbitrap instrument is the independent operation of the orbitrap and the LIT. Because high resolution requires longer transient time, further data can already be collected in the LIT at the same time. As an example accurate mass measurements of the precursor ion can be performed in the orbitrap while MS and MS spectra are recorded with the linear ion trap. The LIT-orbitrap has less resolution than a FT-ICR instrument with similar duty cycle, but its maintenance costs are far lower than for the FT-ICR. Both instruments will have a major impact in mainly qualitative analysis of low molecular weight compounds and macromolecules. 

Advances in high resolution mass analyzers (TOF, FT-ICR, orbitrap) have greatly improved the detection and identification of metabolites based on accurate mass measurements. In single MS mode accurate mass determination is mainly used to differentiate between isobaric ions. Combined with LC-MS, it allows the detection of predicted metabolites by performing extracted ion current profiles... 

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.,... 

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. 

Accordingly, Gordon et al. used synthetic reference compounds for metabolites of bemesetron (MDL 72,222) to evidence proposed structures (Table 7) [37], However, in contrast to the IT and SQ analysers Chen et al., He et al. and Gordon et al. used, more modem mass spectrometers providing high-resolution equipment, e.g. Orbitrap, FT-ICR or double time-of-flight (TOF-TOF), would allow more adequate and precise identification by determination of the accurate mass. 

With respect to MS equipment significant performance improvements are promised by the use of most modem mass analysers (e.g. Orbitrap, FT-ICR, TOF-TOF) that provide highest resolution and mass accuracy important for, e.g. in-depth elucidation of biotransformation. 

This equation shows that the frequency is directly linked to the m/q ratio and is independent of the kinetic energy of the injected ions. This is a very important property of the orbitrap. The broadband current induced by the oscillating ions is measured and converted by an FT to the individual frequencies and intensities, yielding the mass spectrum. 

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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