Mass spectrometry setup

Using the same threshold ionization mass spectrometry setup, Perrin et al. [317] have measured the temporal decay of radical densities in a discharge afterglow. From these experiments the coefficient p for the radical SiH. has been determined to be 0.28, which is in agreement with already known results from other (indirect) experimental approaches [136,137,318]. For the Si2H5 radical is determined to be between 0.1 and 0.3. The coefficient p for atomic hydrogen on a-Si H lies between 0.4 and 1, and is thought to represent mainly surface recombination to H. ... 

Silane and hydrogen show relaxation patterns with the same characteristic time t, however, inverse signs. The fragmentation of silane induced by collisions with electrons, yields molecular hydrogen in an order of magnitude faster than the time resolution of the mass spectrometry setup, i. e. faster than 1 ms. Two possible pathways of silane fragmentation can be regarded ... 

Fig. 1. Schematic outline of the basic ion mobility-mass spectrometry setup using mass selection before (MSI) and after (MS2) the drift tube...

Irradiation Below the Threshold of Ablation with 10 m] cm 2. A Kapton sample was irradiated at 1 Hz repetition rate (to exclude thermal effects) to test whether even below the threshold of ablation any signs of degradation can be observed. After 7,500 pulses small changes in the spectrum are detected. Our mass spectrometry setup is not sensitive enough to detect this small amount of ablation product, but in studies using a quartz microbalance (e.g., [81]) a reduction of the polymer mass at this low fluence was detected. Therefore it can be assumed that (if at all) only portions of the ablation products are trapped within the polymer. The spectra match the previously described changes after irradiation with higher fluences and much lower pulse numbers. 

FIGURE 20.13 Instrumental diagram of an accelerator mass spectrometry setup, the Vienna Environmental Research Accelerator (VERA). Source Vockenhuber, C, et al. (2003) Accelerator mass spectrometry of heavy long-Uved radionuclides. International Journal of Mass Spectrometry, 223-224,713-732. 

Fig. 4.7 Schematic diagram of a flowing afterglow mass spectrometry setup. The system is setup to perform reactions with H3O+. Other primary ions can be generated by other types of ion sources. (Adapted from ref [121] and Smith, D. panel, R Selected ion flow tube mass spectrometry (SlFT-MS) for online trace gas analysis. Mass Spectrom Rev. 24, 2005, 661-700] with permission of Wiley. 2001 and 2005, Wiley, Ltd.)...

Obviously, almost any technique to achieve the goals of ionization, separation and detection of ions in the gas phase can be applied - and actually has been applied -in mass spectrometry. This leads to a simple basic setup having all mass spectrometers in common. A mass spectrometer consists of an ion source, a mass... 

Note Tandem mass spectrometry is also known as MS/MS or MS. The latter terminology elegantly allows for the expansion to multi-stage experimental setups, e.g., MS MS or generally MS . 

Mol, R., de Jong, G. J., and Somsen, G. W. (2005). Online capillary electrophoresis-mass spectrometry using dopant-assisted atmospheric pressure photoionization setup and system performance. Electrophoresis 26, 146—154. 

Biomaterials. Recently, an improved experimental setup for time-resolved insource pyrolysis /py./ field ionization /f.i./ mass spectrometry /m.s./ has been described (10) and examples of its application to studying various biomaterials have been shown. There is a number of characteristic features of the py.-f.i.m.s. that are... 

To preface the presentation of factors affecting kinetics measurements by time-resolved mass spectrometry in the next section, it is useful to see how a typical experimental setup would be configured. The following is a description of the apparatus originally designed and built in the author s laboratory at the University of Minnesota by S. B. Moore [35], and subsequently modified and improved, primarily by Fuxiang Wu. 

Nonporous polymeric membranes have been incorporated as sample inlets in mass spectrometry (MS) for the direct sampling of volatile and semivolatile organic compounds (VOCs and SVOCs). The technique of membrane inlet (introduction) mass spectrometry (MIMS) has achieved tremendous success in the last two decades in terms of instrumentation and applications. Figure 4.1 depicts the experimental setup of (i) in-sample membrane MIMS and (ii) direct insertion (near the ion source in MS) membrane MIMS. 

It seems reasonable that additional hyphenation of mass spectrometry (e.g., LC-NMR-MS) would be an even more powerful approach when considering complex mixtures. Such an LC-NMR-MS setup was first introduced by Bruker... 

In general, any analytical equipment or procedure used in the field of natural products chemistry and environmental engineering is also helpful in aroma analysis 64,65 The history and principles of such art are described in detail elsewhere and will not be featured here. Gas chromatography (GC), GC-mass spectrometry (MS), and nuclear magnetic resonance (NMR) are the most frequently used techniques along with rather specialized setups such as proton transfer reaction-mass spectrometry66 (PTR-MS) used in retronasal aroma analysis (see Chapters 9.02, 9.06, 9.10-9.11). 

Although the software running on the two platforms can control the same mass spectrometry instruments, their designs are very different. The MassChrom software was designed in the early 1990s for operators with mass spectrometry training the terminology and instrument setup within the applications are specialist for trained mass spectrometrists. 

Fig. 11. Experimental setup for the in situ detection of chemisorbed CO during catalytic combustion of CO on Pt using optical infrared-visible sum frequency generation (SFG) and mass spectrometry. A mode-locked Nd YAG laser system is used to provide the visible laser beam (second harmonic 532 nm) and to pump an optical parametric system to generate infrared radiation (wir) tunable with a pulse duration of 25 ps. MC monochromator, PMT Photomultiplier, AES Auger Electron Spectrometer, LEED Low Energy Electron Diffraction Spectrometer, QMS Quadrupole Mass Spectrometers for CO Thermal Desorption (TD) and CO2 production rate measurements.

Historically, pyrolysis-mass spectrometry (Py-MS) was applied to the analysis of biopolymers before Py-GC [45]. However, the first application utilized an off-line setup. In time, several on-line procedures were developed and they became more common. In Py-MS the pyrolysate is directly transferred to the mass spectrometer and analyzed, generating a complex spectrum (sometimes also called a pyrogram, although this should not be confused with the chromatogram of a pyrolysate, also called pyrogram). The ionization process that takes place in the ion source of the mass spectrometer can... 

Recently, a lot of new exj)eriniental results in supersonic beams have been produced in this field [8]. The basic setup of a cluster experiment is following. First, the clusters are prepared in a supersonic beam. Second, the clusters are photodis-soeiated bt a polarized laser beam, and, third the photodissociated fragments are ionized and detee.ted by techniques of mass spectrometry. 

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