Orthogonal acceleration

Orthogonal TOF is the name commonly given to what should properly be called orthogonally accelerated TOF mass spectrometry. Therefore, it is sometimes referred to by the acronym oa-TOF, especially in official publications, but it is more usual to hear it referred to simply as orthogonal TOF. 

Py/GC/MS. pyrolysis, gas chromatography, and mass spectrometry used as a combined technique Py/MS. pyrolysis and mass spectrometry used as a combined technique oa-TOF. orthogonally accelerated time of flight Q. quadrupole field or instrument... 

Figure 5.45 Structures of (1) Bosentan (C27H29N5O6S [M + H]+ 552.1917) and three of its metabolites, formed by (2) oxidation (C27H29N5O7S [M + H]+ 568.1866), (3) demethylation (C26H27N5O6S [M- -H]+ 538.1760), and (4) demethylation-oxidation (C26H27N5O7S [M + M]+ 554.1709). Reprinted by permission of Elsevier Science from Exact mass measurement of product ions for the structural elucidation of drug metabolites with a tandem quadrupole orthogonal-acceleration time-of-flight mass spectrometer , by Hopfgartner, G., Chemushevich, I. V., Covey, T., Plomley, 1. B. and Bonner, R., Journal of the American Society for Mass Spectrometry, Vol. 10, pp. 1305-1314, Copyright 1999 by the American Society for Mass Spectrometry.

Henry, C. M., Electrospray in Flight. Orthogonal acceleration brings the advantages of time of flight to electrospray, Anal. Chem. News Features, 71(5), 197A, 1999. 

Hogenboom A.C. et al., 1999b. Accurate mass determination for the confirmation and identification of organic microcontaminants in surface water using online solid-phase extraction liquid chromatography electrospray orthogonal-acceleration time-of-flightmass spectrometry. Rapid Commun Mass Spectrom 13 125. 

Continuous ion sources, such as ESI, can be connected to the TOF analyzers through orthogonal acceleration (oa-TOF) [205-209]. In oa-TOF, the ions generated by the source enter the TOF analyzer perpendicular to its main axis (Fig. 2.11). The acceleration potential is initially set to zero and the start pulse is generated instantaneously as the potential is raised and the ions are accelerated into the field-free flight tube. 

J. H. J. Dawson and M. Guilhaus. Orthogonal-Acceleration Time-of-Flight Mass Spectrometer. Rapid Commun. Mass Spectrom., 3(1989) 155-159. 

Morris H.R., Paxton T., Dell A., Langhome J., Berg M., Bordoli R.S., Hoyes J., and Bateman R.H. (1996), High sensitivity collisionally-activated decomposition tandem mass spectrometry on a novel quadrupole/orthogonal-acceleration time-of-flight mass spectrometer, Rapid Commun. Mass Spectrom. 10, 889-896. 

Up to here, the discussion has focused on MALDI-TOF equipment, because MALDI is a pulsed ionization method. MALDI initiated tremendous improvements of TOF analyzers which makes it attractive to combine such compact but powerful analyzers with any other non-pulsed ionization method desirable. The major breakthrough came from the design of the orthogonal acceleration TOF analyzer (oaTOF), i.e., a TOF analyzer into which pulses of ions are extracted or-... 

Fig. 4.14. Schematic of an orthogonal acceleration reflector TOP instrument. See text for discussion. Reproduced from Ref. [47] by permission. John Wiley Sons, 2000.

Coles, J. Guilhaus, M. Orthogonal Acceleration - a New Direction for TOF-MS Fast, Sensitive Mass Analysis for Continuous Ion Sources. Trends Anal. Chem. 1993,12, 203-213. 

Selby, D.S. Mlynski, V. Guilhaus, M. A 20 KV Orthogonal Acceleration Time-of-Flight Mass Spectrometer for Matrix-Assisted Laser Desorption/Ionization. Int. 

Laser desorption intrinsically is a pulsed ionization process, which is therefore ideally combined with time-of-flight (TOF) analyzers (Chap. 4.2). [16,49] Ever since the first MALDI experiments, MALDI and TOF have been forming a unit, and the majority of MALDI applications are MALDI-TOF measurements. Vice versa, it was the success of MALDI that pushed forth the tremendous delevopment of TOF mass analyzers. More recently, MALDI has also been adapted to orthogonal acceleration TOF analyzers. [147]... 

Magnetic sector instruments (Chap. 4.3) were used first to demonstrate the beneficial effects of resolution on ESI spectra of biomolecules. [96,103,104] Fourier transform ion cyclotron resonance (FT-ICR, Chap. 4.6) instruments followed. [105-107] The more recently developed orthogonal acceleration of time-of-flight (oaTOF, Chap. 4.2 and 4.7) analyzers also present an effective means to resolve all or at least most peaks. [108-110]... 

Guilhaus, M. Selby, D. Mlynski, V. Orthogonal Acceleration Time-of-Flight-MS. Mass Spectrom. Rev. 2000,19, 65-107. 

Jarvis, S. A., Bateman, R. H., Carruthers, R., Doorbar, P., and Green, M. (1998). A new atmospheric pressure ionization orthogonal acceleration time of flight mass spectrometer. Adv. Mass Spectrom. 14, B044120/1-B044120/7. 

In general the commercial TOP instruments have two detectors one for the linear mode and one for the reflectron mode. The combination of MALDI with TOP is ideal because both techniques are pulsed techniques. However, it is also possible to arrange a continuous beam as generated by electrospray ionization. Por that purpose orthogonal acceleration was developed [65]. The ion beam is introduced perpendicularly to the TOP and packets are accelerated orthogonally (oa-TOP) at similar frequencies improving the sensitivity. While a packet of ions is analyzed, a new beam is formed in the orthogonal acceleration. 

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. 

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