Space mass spectrometry

Head-Space Gas Chromatography or Head-Space Mass Spectrometry... 

All reagents are commercially available. For the gas chromatography approach, isopropylamine may be used as an internal standard [28]. It is dried over granular calcium chloride. TMA is purchased as the hydrochloride salt and TMA N-oxide as the dehydrate (Sigma, UK). TMA and TMA N-oxide are stored in desiccators over silica gel and are heated at 105 C for 2 h prior to use [28]. For head-space mass spectrometry, [2H9]-TMA is purchased from Cambridge Isotope Laboratories (UK) [27]. 

In 1985 chemists at Rice University in Texas used a high-powered laser to vaporize graphite in an effort to create unusual molecules believed to exist in interstellar space. Mass spectrometry revealed that one of the products was an unknown species with the formula Ceo- Because of its size and the fact that it is pure carbon, this molecule has an exotic shape, which the researchers worked out using paper, scissors, and tape. Subsequent spectroscopic and X-ray measurements confirmed that Ceo is shaped like a hollow sphere with a carbon atom at each of the 60 vertices. Geometrically, buckyball (short for buckminsterfullerene ) is the most symmetrical molecule known. In spite of its unique features, however, its bonding scheme is straightforward. Each carbon is xp -hybridized, and there are extensive delocalized molecular orbitals over the entire structure. 

Cerrato Oliveros, C., Boggia, R., Casale, M., Armanino, C., and Forina, M. Optimisation of a new head-space mass spectrometry instrument. Discrimination of different geographical origin olive oils. Journal of Chromatography A, 1076, 7-15. 2005. 

W. Cynkar, D. Cozzolino, B. Dambergs, L. Janik, M. Gishen, Feasibility study on the use of a head space mass spectrometry electronic nose (MS e-nose) to monitor red wine spoilage mducedhy Brettanomyces yeast. Sensors Actuators B Chem. 124, 167-171 (2007)... 

M. Cocchi, C. Durante, A. Marchetti, C. Armanino, M. Casale, Characterization and discrimination of different aged Aceto balsamico tradizionale di modena products by head space mass spectrometry and chemometrics. Anal. Chimica Acta 589, 96-104 (2007)... 

Cozzolino D, Smyth HE, Cynka W, et al. Use of direct head-space mass spectrometry coupled with chemometiics to predict aroma properties in Australian Riesling wine. Anal Chim Acta. 2008 621 2-7. 

MS-MS in an ion-trap instrument is fundamentally different from MS-MS in sector and triple-quadru-pole instruments. While in the latter the various stages of the process, i.e. precursor ion selection, CID and product-ion mass analysis are performed in different spatial regions of the instrument, in ion-trap instruments these stages are performed consecutively within the ion trap itself. It is tandem-in-time rather than tandem-in-space mass spectrometry. A simplified diagram of an ion-trap system is shown in Figure ID. 

HS-fluorescence spectroscopy, head space-fluorescence spectroscopy EMM, excitation and emission matrices SVM, support vector machine HS-MS, head-space mass spectrometry HPLC-CAD, HPLC coupling to charged aerosol MCR-FMIN, multivariate curve resolution based on the minimization of an objective KNN, fe-nearest neighbour CPANN, counter-propagation artificial neural network. ... 

Schlager H and Arnold F 1985 Balloon-borne fragment ion mass spectrometry studies of stratospheric positive ions unambiguous detection of H (CH3CN), (H20)-clusters Pianet. Space Sc/. 33 1363-6... 

There is potential confusion in the use of the word array in mass spectrometry. Historically, array has been used to describe an assemblage of small single-point ion detectors (elements), each of which acts as a separate ion current generator. Thus, arrival of ions in one of the array elements generates an ion current specifically from that element. An ion of any given m/z value is collected by one of the elements of the array. An ion of different m/z value is collected by another element. Ions of different m/z value are dispersed in space over the face of the array, and the ions are detected by m/z value at different elements (Figure 30.4). 

Some of the target molecules gain so much excess internal energy in a short space of time that they lose an electron and become ions. These are the molecular cation-radicals found in mass spectrometry by the direct absorption of radiation. However, these initial ions may react with accompanying neutral molecules, as in chemical ionization, to produce protonated molecules. 

Mass Spectra and Chemical Structure While there are a number of books (Refs 16, 30, 49 64) already referred to, which deal with details of the instrumentation and techniques of mass spectrometry, there are several concise introductory texts (Refs 10, 21 52) on the interpretation of mass spectra. Still other recent books deal comprehensively with organic structural investigation by mass spectrometry. One of these (Ref 63) discusses fundamentals of ion fragmentation mechanisms, while the others (Refs 7, 15, 20, 28 29) describe mass spectra of various classes of organic compounds. In the alloted space for this article methods of interpretation of mass spectra and structural identification can not be described in depth. An attempt is, therefore, made only to briefly outline the procedures used in this interpretation... 

ESI mass spectra of mixtures are difficult to interpret, because each component produces ions with many different charge states. The most direct and reliable method to solve this problem is to use high-resolution MS and calculate the charge states by measuring the spacing of the isotope peaks. ESI mass spectrometry of (polymeric) mixtures with broad molecular weight distribution benefits from a prior separation that reduces the polydispersity of the analyte. 

Appropriate use of RF and DC voltages means that some ions can be selectively retained and product ions generated. Some of these ions can then be selected and their product ions generated. In this manner, a fragmentation chain can be established. The ion trap is a typical tandem-in-time mass spectrometer, in which precursor and product ions are created and analysed in the same physical space ionisation and ion analysis, on the other hand, take place at different times ( MS/MS in time )- The operation can be repeated several times, making it possible to perform MS11. Ion trap mass spectrometry thus consists of ... 

Ledford, E. B., Jr. Rempel, D. L. Gross, M. L. Space charge effects in Fourier transform mass spectrometry Mass calibration. Anal. Chem. 1984,56, 2744-2748. 

The concept of peak capacity is rather universal in instrumental analytical chemistry. For example, one can resolve components in time as in column chromatography or space, similar to the planar separation systems however, the concept transcends chromatography. Mass spectrometry, for example, a powerful detection method, which is often the detector of choice for complex samples after separation by chromatography, is a separation system itself. Mass spectrometry can separate samples in time when the mass filter is scanned, for example, when the mass-to-charge ratio is scanned in a quadrupole detector. The sample can also be separated in time with a time-of-flight (TOF) mass detector so that the arrival time is related to the mass-to-charge ratio. 

Frahm, J.L., Howard, B.E., Heber, S., Muddiman, D.C. (2006). Accessible proteomics space and its implications for peak capacity for zero-, one-, and two-dimensional separations coupled with FT-ICR and TOF mass spectrometry. J. Mass Spectrom. 41, 281-288. 

Figure 2.14 Tandem mass spectrometry product ion scan experiments in space (a) and in time (b)...

A number of other laser spectroscopic techniques are of interest but space does not permit their discussion. A few specialized methods of detecting laser absorption worthy of mention include multiphoton ionization/mass spectrometry (28), which is extremely sensitive as well as mass selective for gas-phase systems optically detected magnetic resonance (29) laser intracavity absorption, which can be extremely sensitive and is applicable to gases or solutions (30) thermal blooming, which is also applicable to very weak absorbances in gases or liquids (31) and... 

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