Time-of-flight mass spectrometry ToFMS

There are at least three approaches to fast GC/MS (1) use of microbore columns with time-of-flight mass spectrometry (TOFMS) (2) use of low-pressure (LP)-GC/MS to aid separations at increased flow rate " and (3) use of supersonic molecular beam mass spectrometry (SMBMS) (also known as supersonic GC/MS), which can accept increased flow rates and short analytical columns."... 

Resolutions in the range of 10,000 to 20,000 are achievable with modem time-of-flight mass spectrometry (TOFMS). Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) is more costly but capable of resolutions exceeding 100,000. Resolutions exceeding 10,000 can provide low to sub parts-per-million mass accuracies. One ppm is equivalent to a mass accuracy of 0.001 for a molecular weight of 1,000 Da. 

Time of Flight The principle of time-of-flight mass spectrometry (TOFMS) is very simple and makes use of the energy equation E = mv2/2 where m is mass and v is velocity. As illustrated in Figure 11.1, all ions are accelerated to constant energy E. The ions then enter a drift tube where they travel at velocity v. Because each ion mass m travels at a different velocity, the ions of different mass separate the lighter ones run ahead of the heavier ones. This separation means that each ion mass hits the detector at a different time. Ions of the same... 

Fig. 15.6 GCxGC time-of-flight mass spectrometry (TOFMS) total ion chromatogram of coriander essential oil as a contour plot. Reprinted with permission from [37]. Copyright (2005)...

Time-of-flight mass spectrometry (TOFMS) is an alternative to scanning-based mass analyzers. Coupled to ICP it can produce a complete mass spectrum in less than 50 /rsec. CGC combined with ICP-TOFMS has been developed for the speciation of Hg " ° and later improved by MCGC-ICP-TOFS "" allowing complete chromatographic separation within a chromatographic runtime of less than 1 min. 

Time-of-flight mass spectrometry (TOFMS) is probably the simplest method of mass spectrometric measurement by the physical principle. The key features of TOFMS are extreme sensitivity (all ions are detected), practically unlimited mass range and as well as high-speed analysis (recent TOFMS instruments are able to measure hundreds full spectra per second). This all makes TOFMS one of the most desirable methods of mass analysis (Schlag, 1994 Guilhaus, 1995). The general scheme of TOFMS is shown in Scheme 1. 

Efforts to decrease analytical times have largely depended on improved response times in detectors. Fast GC, where complete separations are achieved in a few minutes, has a number of reported applications. Time-of-flight mass spectrometry (TOFMS) is often... 

For the characterization (compound identification) of the bands eluting from a fast gas chromatographic separation, time-of-flight mass spectrometry (TOFMS) is unsurpassed. The two unique attributes of TOFMS that make it so well suited as a detector for HSGC are very high spectral acquisition rates and spectral continuity across the chromatographic peak profile for a single-component peak (31). 

In addition to the main lines of research treated above, research into reflection electron microscopy (REM) and time-of-flight mass spectrometry (TOFMS) was also pursued in the Electron Microscopy Department. Investigations of catalyst surfaces, metals, zeolites and polymer films all offered potential bridges to work in other departments, but such opportunities were rarely realized. Hence, electron optical and electron spectroscopic techniques provided only a loose bond between the separate lines of specialized research at the EHL... 

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