TOF-reflectron

Figure 6.4 Expanded portion of the MALDI-TOF mass spectra of two different clinical isolates (by region) of Vibrio parahaemolyticus obtained on a reflectron TOF/MS, showing a single change in mass of a protein from m/z 9479 to mtz 9587 giving rise to the strain and geography-related differences observed in Figure 6.3 and reported in Wilkes et al.54...

Both collisional activation (in ion traps) and post source decay (in curved field reflectron TOF analyzers) have been used successfully to obtain sequence ions from peptides prepared in situ on the sample holder. Single Dalton mass windows are advantageous for precursor selection, as are realized in ion-trap and trap-TOF configurations. Publicly available search algorithms can be used... 

The advent of ultrafast pump-probe laser techniques62 and their marriage with the TOF method also enables study of internal ion-molecule reactions in clus-ters.21,63-69 The apparatus used in our experiments is a reflectron TOF mass spectrometer coupled with a femtosecond laser system. An overview of the laser system is shown in Figure 4. Femtosecond laser pulses are generated by a colliding pulse mode-locked (CPM) ring dye laser. The cavity consists of a gain jet, a... 

Figure 14. Reflectron-TOF spectra of acetone (T) cluster ions. Am (T)mH+, Bm (T)mCH5, Cm = (T)mC2H30+. (a) 0.4% water in the acetone sample, (T)i C6HnO+ (mass 157) and (T)2-C6HnO+ (mass 215) are seen, whereas ion signal corresponds to (T)3-H30+ (mass 193 is not found), (b) 0.7% water in the acetone sample, all peaks corresponding to masses 157, 215, and 193 are observed, (c) 1.0% water in the acetone sample, ion peaks corresponding to (T)vC6HnO+ (mass 157) and (T)2 C6HnO+ (mass 215) are not seen however, (T)3-H30+ (mass 193) is clearly identified. Neutral clusters are ionized at 355 nm using a pulsed Nd YAG laser. Taken with permission from ref. 2.

Elucidating the origin of magic numbers has been a problem of long-standing interest, made accessible through the use of the laser-based reflectron TOF technique and evaporative ensemble theory. Three test cases are considered, first protonated ammonia clusters where (NH3)4 NHj has been found to be especially prominent, and then two other cases are considered, one involving water cluster ions and another rare gas clusters. 

Fig. 4.8. Coaxial curved-field reflectron TOF spectrometer. The total length is about 1 m. Adapted from Ref. [37] with permission. John WUey Sons, 1995.

Cordero, M.M. Cornish, T.J. Cotter, R.J. Lys, LA. Sequencing Peptides Without Scanning the Reflectron Post-Source Decay With a Curved-Field Reflectron TOF Spectrometer. Rapid Commun. Mass Spectrom. 1995, 9, 1356-1361. 

Strobel, F.H. Solouki, T. White, M.A. Russell, D.H. Detection of Femtomole and Sub-Femtomole Levels of Peptides by Tandem Magnetic Sector/Reflectron TOF Mass Spectrometry and MALDI. J. Am. Soc. Mass Spectrom. 1991,2, 91-94. 

Aicher, K.P. Muller, M. Wilhelm, U. Grotemeyer, J. Design and Setup of an Ion Trap-Reflectron-TOF Mass Spectrometer. Eur. Mass Spectrom. 1995, 1, 331-340. 

Mamyrin, B.A. Laser Assisted Reflectron-TOF-MS. Int. J. Mass Spectrom. Ion Proc. 1994,757, 1-19. 

Several commercial instrument designs have effectively overcome this inherent problem and can record high-energy CID product ion spectra. The Applied Biosystems 4700 Proteomics Analyzer was one of the two originally available commercial TOF/TOF designs76,77 (Fig. 24). When the instrument is operated to obtain a mass spectrum, it acts as a standard inline reflectron TOF instrument. In product ion experiments the precursor ion is isolated at the end of the first flight tube by the timed-ion selectors (TIS). The MALDI source uses DE to correct for... 

The major deficiency of a simple linear TOF instrument is its insufficient mass resolution, resulting from flight time variations of ions of the same m/e ratio. The ionization process adds a certain amount of initial kinetic energy to the molecules before acceleration. In addition, the different spatial positions in the source from where the ions are formed lead to varying values of l, and thus to flight time variations. As a result, modern TOF instruments commonly employ a technique called reflection to enhance resolution. A reflectron TOF (RETOF) [4] (Fig. 3) is used to focus ions of the same... 

Ions produced by SPI are detected and mass analyzed by a reflectron TOF mass spectrometer having a resolution of m/Am = 1000. The sample is introduced into the... 

There are several types of ionization sources [MALDI, ESI, FAB (fast atom bombardment), PD (Cf-252 plasma desorption), El (electron ionization), Cl (chemical ionization) etc.], different types of mass analyzers [combinations of magnetic and electric sectors, quadrupolar filters (Q) and ion traps (IT), time-of-flight (TOF) and FT-ICR] and different detectors, each with its own advantages and drawbacks. We describe herein only the systems that presently have widespread use for the study of biomolecules ESI coupled to a quadrupole (or triple quadrupole, QqQ) mass analyzer or an ion trap, the MALDI source with the linear or reflectron TOF analyzer, and the FT-ICR system which can be equipped with both ESI and MALDI sources. 

Fig. 20 Reflectron TOF spectra obtained after excitation using 800 nm variable pulse widths between 80 fs and 70 ps. All the traces have been normalized to have the same Fe+ mass peak intensity. Adapted from [48]...

B. SPENGLER, D. KIRSCH and R. KAUFMANN obtain structural information with reflectron TOF mass spectrometry (MALDI post-source decay) [66],... 

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