Time-of-flight tandem mass spectrometers

B. Warscheid, K. Jackson, C. Sutton, and C. Fenselau. MALDI Analysis of Bacilli in Spore Mixtures by Applying a Quadrupole Ion Trap Time-of-Flight Tandem Mass Spectrometer. Anal. Chem., 75(2003) 5608-5617. 

Xia, Y. Thomson, B.A. McLuckey, S.A. Bi-directional ion transfer between quadrupole arrays MS" ion/ion reaction experiments on a quadrupole/time-of-flight tandem mass spectrometer. Anal. Chem. 2007, 79, 8199-8206. 

C. Borchers, C. E. Parker, L. J. Deterding, and K. B. Tomer, Preliminary comparison of precursor scans and liquid chromatography on a hybrid quadrupole time-of-flight tandem mass spectrometer, J. Chromatogr. A 854, 119-130 (1999). 

Nakanishi T, Ohtsu I, Furuta M, Ando E, Nishimura O. Direct MS/MS analysis of proteins blotted on membranes by a matrix-assisted laser desorption/ionization-quadrupole ion trap-time-of-flight tandem mass spectrometer. J Proteome Res 2005 4 743-747. 

Warscheid B, Jackson K, Sutton C, Fenselau C. MALDI analysis of Bacilli in spore mixtures by applying a quadrupole ion trap time-of-flight tandem mass spectrometer. Anal Chem. 2003 75 5608-17. 

Quadrupole Time-of-Flight Tandem Mass Spectrometers... 

Morelle, W. Slomianny, M.-C. Diemer, H. Schaeffer, C. van Dorsselaer, A. Michalski, J.-C. Structural characterization of 2-aminobenzamide-derivatized oligosaccharides using a matrix-assisted laser desorption/ionization two-stage time-of-flight tandem mass spectrometer. Rapid Commun. Mass Spectrom. 2005, 19, 2075-2084. 

Figure 2.3. A. Mass spectrometer consisting of an ionization source, a mass analyzer and an ion detector. The mass analyzer shown is a time-of -flight (TOF) mass spectrometer. Mass-to-charge (m/z) ratios are determined hy measuring the amount of time it takes an ion to reach the detector. B. Tandem mass spectrometer consisting of an ion source, a first mass analyzer, a collision cell, a second mass analyzer and a detector. The first mass analyzer is used to choose a particular peptide ion to send to the collision cell where the peptide is fragmented. The mass of the spectrum of fragments is determined in the second mass analyzer and is diagnostic of the amino acid sequence of the peptide. Figure adapted from Yates III (2000).

A linear time-of-flight (TOP) mass spectrometer is not suited to MS/MS experiments. Considering the wide popularity of TOP instruments, it was natural that a tandem MS instrument based on this geometry is developed. Some of the developments in this field are described below. 

The TOF mass analyzer has a low duty cycle, and the combination with an ion accumulation device such as an ion trap is therefore very advantageous. It offers also MS capabilities with accurate mass measurement. In all acquisition modes, the ions are accelerated into the time of flight for mass analysis. Various other hybrid mass spectrometers with TOF have been described, including quadrupole ion trap [70] and linear ion trap [58]. High energy tandem mass spectrometry can be performed on TOF-TOF mass spectrometers [71, 72]. 

Finally, it is important to note there are many other instruments and configurations that are often referred to as tandem mass spectrometers. There are hybrid instruments that use another form of mass separation, time-of-flight (TOF) mass spectrometry. TOF mass spectrometry separates ions based on the time it takes to... 

Tandem mass spectrometry (MS/MS) is a method for obtaining sequence and structural information by measurement of the mass-to-charge ratios of ionized molecules before and after dissociation reactions within a mass spectrometer which consists essentially of two mass spectrometers in tandem. In the first step, precursor ions are selected for further fragmentation by energy impact and interaction with a collision gas. The generated product ions can be analyzed by a second scan step. MS/MS measurements of peptides can be performed using electrospray or matrix-assisted laser desorption/ionization in combination with triple quadruple, ion trap, quadrupole-TOF (time-of-flight), TOF-TOF or ion cyclotron resonance MS. Tandem... 

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.

It should be pointed out that FAB, MALDI, and ESI can be used to provide ions for peptide mass maps or for microsequencing and that any kind of ion analyzer can support searches based only on molecular masses. Fragment or sequence ions are provided by instruments that can both select precursor ions and record their fragmentation. Such mass spectrometers include ion traps, Fourier transform ion cyclotron resonance, tandem quadrupole, tandem magnetic sector, several configurations of time-of-flight (TOF) analyzers, and hybrid systems such as quadrupole-TOF and ion trap-TOF analyzers. 

The instrumental analysis for the identification of UV filters degradation products formed during the fungal treatment process was performed by means of HPLC coupled to tandem mass spectrometry using a hybrid quadrupole-time-of-flight mass spectrometer (HPLC-QqTOF-MS/MS). Chromatographic separation was achieved on a Hibar Purospher STAR HR R-18 ec. (50 mm x 2.0 mm, 5 pm, from Merck). In the optimized method, the mobile phase consisted of a mixture of HPLC grade water and acetonitrile, both with 0.15% formic acid. The injection volume was set to 10 pL and the mobile phase flow-rate to 0.3 mL/min. 

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