Qtof

Different options are available for LC-MS instruments. The vacuum system of a mass spectrometer typically will accept liquid flows in the range of 10-20 p,L min-1. For higher flow-rates it is necessary to modify the vacuum system (TSP interface), to remove the solvent before entry into the ion source (MB interface) or to split the effluent of the column (DLI interface). In the latter case only a small fraction (10-20 iLrnin ) of the total effluent is introduced into the ion source, where the mobile phase provides for chemical ionisation of the sample. The currently available commercial LC-MS systems (Table 7.48) differ widely in characteristics mass spectrometer (QMS, QQQ, QITMS, ToF-MS, B, B-QITMS, QToF-MS), mass range m/z 25000), resolution (up to 5000), mass accuracy (at best <5ppm), scan speed (up to 13000Das-1), interface (usually ESP/ISP and APCI, nanospray, PB, CF-FAB). There is no single LC-MS interface and ionisation mode that is readily suitable for all compounds... 

QToF-MS >20 000 ESI, APCI, MALDI Mass accuracy <5 ppm (m/z 150-900) resolution 5000 nanoflow... 

High vacuum and high accelerating voltages QToF-MS for true MS/MS resolution (Am) decreases with increasing mass... 

Vonderheide, A.P., Mounicou, S., Meija, J., Henry, H.F., Caruso, J.A., and Shann, J.R., Investigation of selenium-containing root exudates of Brassica juncea using HPLC-ICP-MS and ESI-qTOF-MS, Analyst, 131, 33-40, 2006. 

Different mass analysers can be combined with the electrospray ionization source to effect analysis. These include magnetic sector analysers, quadrupole filter (Q), quadrupole ion trap (QIT), time of flight (TOF), and more recently the Fourrier transform ion cyclotron resonance (FTICR) mass analysers. Tandem mass spectrometry can also be effected by combining one or more mass analysers in tandem, as in a triple quadrupole or a QTOF. The first analyzer is usually used as a mass filter to select parent ions that can be fragmented and analyzed by subsequent analysers. 

Chlamydia trachomatis Phosphate/KCl RP trap QTOF Global Ultima MassLynx (Skipp et al., 2005)... 

The ability to resolve and characterize complicated protein mixtures by the combination of 2DLC and online mass spectrometry permits the combination of sample fractionation/simplification, top-down protein mass information, and bottom-up peptide level studies. In our lab, the simplified fractions generated by 2D(IEX-RP)LC are digested and analyzed using common peptide-level analysis approaches, including peptide mass fingerprinting (Henzel et al., 1993 Mann et al., 1993), matrix-assisted laser desorption/ionization (MALDI) QTOF MS/MS (Millea et al., 2006), and various capillary LC/MS/MS methodologies (e.g., Ducret et al., 1998). 

Sectors(EB 8E EBE Quadnipole (Q, QqQ) Ion trap, Orbitrap Time of flight (TOP) Hybrids (BEqQ QTOF.)... 

Farag M.A. Wessjohann L A. Metabolome classification of commercial hypericum perforatum (StJohn s Wort) preparations via UPLC-qTOF-MS and chemometrics. PlantaMedica, 2012, 78 (5), 488-496. 

Metelmann, W. Peter-Katalinic, J. Mtithing, J. Ganghosides From Human Granulocytes a Nano-ESl QTOF-MS Fn-cosylation Study of Low Abundance Species in Complex Mixtures. J. Am. Soc. Mass Spectrom. 2001,12, 964-973. 

Reverse-phase columns with a gradient elution in combination with UV-Vis spectrophotometers using photodiode-array (PDA) (Fig. 1.6) and spectrofiuorimeters are common devices employed in this technique. In a lesser extent, MS, tandem mass spectrometry (MS-MS), and nano liquid chromatography-electrospray ionization-quadrupole time-of-flight tandem mass spectrometry (nanoLC-nanoESI-Q-qTOF-MS-MS) has been used as detection system. This instrumentation has been mainly used in the analysis of dyes and proteinaceous media, and in some extent, in the analysis of drying oils and terpenoid varnishes [47,48],... 

All major mass spectrometer manufacturers produce suitable instruments for steroid analyses. Typical instruments used in steroid assays are the Applied Biosystems API 2000-5000 series (www.appliedbiosytems.com), the Finnigan TSQ quantum (www. thermo.com), Agilent QQQ or QTof instruments (www.Agilent.com), and Micromass Quattro instruments (www.waters.com). 

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. 

In addition to MS/MS with CID to obtain structural information, it is also useful to use high-resolution exact mass measurements to confirm the elemental compositions of ions. Essentially, exact mass measurements permit the unambiguous composition analysis of low-molecular-weight compounds (mol. wt. <500) through precise and accurate mlz measurements. The types of mass spectrometers capable of exact mass measurements include magnetic sector mass spectrometers, QTOF hybrid... 

FTICR, Fourier transform ion cyclotron resonance QTOF, quadropole time-of-flight TOF, time-of-flight. 

Arora, V. K., Li, Y., Philip, T., Yeola, S., and Mayol, R. F. (2001). Automated high-throughput metabolite identification using quadrupole time-of-flight (QTOF 2) mass spectrometer. In Proceeding of the 49th ASMS Conference on Mass Spectrometry and Allied Topics, Chicago, IL. 

K. Alving, H. Paulsen, and J. Peter-Katalinic, Characterization of O-glycosylation sites in MUC2 glycopeptides by nanoelectrospray QTOF mass spectrometry, J. Mass Spectrom., 34 (1999) 395-407. 

Figure 4.5 NCE/ESI QTOF-MS and tandem MS electropherograms of DNA-binding domain of human TTAGGG repeat binding factor 2 (hTRF2 DBD) protein. (A) Mass electropherogram of hTRF2 DBD [M+ 5H]S+ ion at m/z 1509, and (B) top-down by CID MS/MS of ion corresponding to the peak number 5 at 10.88 min [8],...

The quadrupole/time-of-flight analyzer (QToF) has become a key option in the qualitative and quantitative analytical arena. Instruments with resolving power of 20000 (50% valley definition) can provide <5ppm mass accuracy for parent and product ion identification and for 20mda mass selection windows quantitation. While the triple quadra-pole retains the lead in sensitivity for quantification, the QToF has a decided edge on specificity (Micromass, 1999) and qualitative analysis. 

The ESI-LC/MS-based approaches that feature ion trap (Gatlin et al, 1998 Washburn et ah, 2001) and quadrupole time-of-flight (QTOF) (Blackburn and Moseley, 1999) mass spectrometers are routinely used for the identification and characterization of proteins. Nanoelectrospray LC/MS formats (Figure 6.3) are used to provide lower limits of detection and fully automated sample preconcentration and desalting. On-line LC/MS approaches for protein expression profiling are also used with ESI-TOF (Banks and Gulcicek, 1997 Chong et al., 2001) and ESI-Fourier transform (FT) (Kelleher... 

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