Orthogonal Acceleration TOF Mass Spectrometer

GC/MS system gas chromatograph Agilent 6890N, equipped with automatic injector, Agilent 7683 with a 100-vial tray, and split/splitless injector with electronic pressure control (EPC) up to 150 psi combined with orthogonal acceleration TOF mass spectrometer, model GCT premier (Waters Corp., Milford, MA). 

Figure 10.11. Orthogonal acceleration TOF mass spectrometers, (a) Original design of Dawson and Guilhaus using lens focusing, (b) An oaTOF shown with an electrospray source and RF ion guide.

Hieftje and co-workers first reported a design for ICP-ToF mass spectrometric systems with both orthogonal acceleration (oa) and axial acceleration (aa) geometry.39 11 The different experimental setups of ICP-ToF mass spectrometers with orthogonal and axial acceleration are compared in Figures 5.10 and 5.11. Both instruments possess a time-of-flight analyzer with a reflectron to improve the mass resolution. 

M. GUILHAUS [55] and A.F. DODONOV [56] describe the orthogonal acceleration time-of-flight (oa-TOF) mass spectrometer. The concept of this technique was initially proposed in 1964 by G.J. O Halloran of Bendix Corporation [57],... 

Hoyes, J. B., Jones, C., Langridge, J. I., Miliar, A., Vissers, J. P. (2002). A novel precursor ion discovery method on a hybrid quadrupole orthogonal acceleration time-of-flight (Q-TOF) mass spectrometer for studying protein phosphorylation. 

Time-of-fiight instruments are configured as either a stand-alone TOF mass analyzer (TOF MS) or as a hybrid quadrupole time-of-fiight (QqTOF) mass spectrometer the latter consists of a quadmpole front-end and an orthogonal acceleration TOF back-end for MS/MS experiments (Fig. 6.10). The orthogonal design minimizes the ions initial velocity spread as they are accelerated into the TOF by a pulsed potential. A QqTOF can be operated as a TOF mass analyzer (QqTOF MS, full-scan) or a quadmpole TOF tandem mass spectrometer (QqTOF MS/MS, product ion scan). Compared to a TOF MS, the... 

Perhaps an encouraging sign is the recent commercialization by MicroMass of a new benchtop orthogonal acceleration time-of-flight (oa-TOF) mass spectrometer that offers field ionization as an accessory. This is the first commercial FI-MS system that is not coimected to a magnetic sector instrument. Hopefully this may open up the FI-MS technique to a new generation of users. 

Fig. 6.9 Schematic view of the lA-TOF system. Gas-phase sample molecules are ionized by alkali metal ion attachment and become adduct ions in the lA ion source. The adduct ions are extracted through the aperture into the differential pumping region, pass through the skimmer, and are introduced into the TOF mass spectrometer. Because 100 Pa of gas is introduced into the lA ion source, a differential pumping system is used to evacuate the gas since the TOF mass spectrometer must be kept in a high vacuum condition. The orthogonal acceleration reflector TOF mass spectrometer realizes mass spectrometry with a high mass resolution over a wide mass range. (Reprinted with permission from Ref [88]. 2007, John Wiley and Sons)...

Principle of the combination of a mass spectrometer with an oa-TOF spectrometer. Ions coming from the mass spectrometer are directed to the detector. When a pulse voltage is applied to the orthogonal acceleration repeller, the ions are analysed by the TOF instrument. 

The conceptual simplicity of TOF-MS disappears when one considers actual instrumentation design. A good understanding of this issue is important in the selection and use of TOP mass spectrometers because there is a good deal of confusion about the true significance of terms like hnear, reflectron, orthogonal acceleration, delayed extraction, and so forth. This may lead to poor selection and use of instriunents. 

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