Online mass spectrometry

The ability to resolve and characterize complicated protein mixtures by the combination of 2DLC and online mass spectrometry permits the combination of sample fractionation/simplification, top-down protein mass information, and bottom-up peptide level studies. In our lab, the simplified fractions generated by 2D(IEX-RP)LC are digested and analyzed using common peptide-level analysis approaches, including peptide mass fingerprinting (Henzel et al., 1993 Mann et al., 1993), matrix-assisted laser desorption/ionization (MALDI) QTOF MS/MS (Millea et al., 2006), and various capillary LC/MS/MS methodologies (e.g., Ducret et al., 1998). 

E. Heinzle, K. Furukawa, I. J. Dunn, and J. R. Bourne, Experimental methods for online mass spectrometry in fermentation technology, Bio/Technol. 1, 181-188 (1983). 

Brum, J. 8t Dell Orco, P., Online mass spectrometry Real-time monitoring and kinetics analysis for the photolysis of idoxifene Rapid Commun. Mass Spectrom. 1998, 12, 741-745. 

The catalyst had been running under butane for 2 h at 873 K when the gas stream was switched from butane to argon. Online mass spectrometry indicated that all hydrocarbon components were rapidly swept out of the reactor at 873 K and no... 

AJ Tomlinson, JM Benson, KL Johnson, S Naylor. Investigation of drug metabolism using capillary electrophoresis with photodiode array detection and online mass spectrometry equipped with an array detector. Electrophoresis 15 62, 1994. 

REDUCTION OF Ni(ll) IONS BY HYPOPHOSPHITE STUDIED BY ONLINE MASS SPECTROMETRY... 

Online mass spectrometry data presented and discussed in the previous sections suggest that catalytic hypophosphite oxidation on nickel in D2O solutions proceeds via the coupling of anodic (19.11) and cathodic (19.12) half-reactions at the catalyst surface. The classical mixed-potential theory for simultaneously occurring electrochemical partial reactions [14] presupposes the catalyst surface to be equally accessible for both anodic (19.11) and cathodic (19.12) half-reactions. Equilibrium mixtures of H2, HD, and D2 should be formed in this case due to the statistical recombination of Hahalf-reactions (19.11) and (19.12) for example, the catalytic oxidation of hypophosphite on nickel in D20 solution under open-circuit conditions should result in the formation of gas containing equal amounts of hydrogen and deuterium (H/D=l) with the distribution H2 HD D2= 1 2 1 (the probability of HD molecule formation is twice as high as for either H2 or D2 formation [75]). Therefore, to get further mechanistic insight, the distribution of H2, HD, and D2 species in the evolved gas was compared to the equilibrium values at the respective deuterium content [54]. 

Only the final product of the process (19.10), that is, molecular hydrogen (H2, HD, and D2), can be detected by online mass spectrometry. However, the catalyst microstructure may be reconstructed by the computer simulation, since the gas evolved remembers the surrounding hydrogen atoms in the environs Had and Dad atoms serve as peculiar markers of reactions (19.11) and (19.12) and thereby define on which site—either anodic or cathodic—they appear. The location of reactions (19.11) and (19.12) at specific site ensembles seems to be probable, taking into account a heterogeneity (structural, chemical, and energetic) of the real catalyst surface. This could be reconstructed from the H2, HD, and D2 distribution in the gas. 

FIGURE 19.4 Representative simulated distributions of Ilad (o) and Dad ( ) atoms in the lattice gas on the nickel surface developed in reactions (19.11) and (19.12), respectively, leading to the formation of the gas mixtures with H2, HD, and D2 content equal to that detected using online mass spectrometry (Figure 19.3B). N—the number of transformations starting from random distribution at a defined H/D ratio to achieve H2, HD, and D2 content equal to that found experimentally at corresponding potentials. (From Jusys, Z. and Vaskelis, A., Ber. Bunsenges. Phys. Chem., 101, 1865, 1997.)... 

Since reaction (19.12) is the only source of deuterium in the course of electroless Ni-P deposition, the rate of reactions (19.11) and (19.12) can be studied by online mass spectrometry under open-circuit conditions as well as a function of the electrode potential similar to analogous measurements in Ni(II)-ffee hypophosphite solutions (see Sections 19.6.1 and 19.6.2). To avoid changes in the membrane permeability due to nickel deposition, each measurement has been carried out on a new specimen of the Ni-sputtered Teflon membrane. 

Online mass spectrometry data listed in Table 19.1 show decrease in the deuterium content in the evolving gas from 36 mol% in Ni(II)-free solution to 5-10 mol% in the presence of Ni(II) under open-circuit conditions. This is in accordance with the literature data of mass spectrometric analysis of the isotopic composition of the gas evolved in various electroless plating solutions [64,65] and... 

Fig. 18. Formation of N2, N2O, and H2O measured by online mass spectrometry in a temperature programmed oxidation experiment after ammonia oxidation at 323 K (lOK/min, 1.0 vol% 02/He flow of 40cm /min).

The surface intermediates formed in the photocatalytic oxidation of propane has been investigated over anatase, rutile, and mixed-phase anatase-rutile Ti02 nanoparticles [26]. Detailed spectroscopic analysis of surface intermediates was conducted via simultaneous in situ FTIR with online mass spectrometry (MS), which was used to follow the decline of propane and formation of carbon dioxide under irradiation by a 400 W Xe lamp. 

From the above, it can be seen that most of the degradation factors in ESs are related to the electrolyte. Hahn et al. [91] used online mass spectrometry (differential eleetrochemical mass spectrometry, DEMS) to analyze the gas products evolved in an EDLC with AC electrodes in 1 M TEABF4/PC during the charging/ overcharging process. CO2 (m/z = 44), propene (m/z = 41), and H2(m/z = 2) were... 

Schnaidt J, Heinen M, Denot D, Jusys Z, Jurgen Behm R (2011) Electrooxidation of glycerol studied by combined in situ IR spectroscopy and online mass spectrometry under continuous flow conditions. J Electroanal Chem 661 250-264... 

Schmidt, V.M., D. Tegtmeyer, and J. Heitbaum. 1995. Transport of protons and water through polyaniline membranes studied with online mass-spectrometry. / Electroanal Chem 385 149. 

Online mass spectrometry is very useful for obtaining process information concerning the molecular composition and structure of unknown compounds and for monitoring an analyte in a complex matrix, and has been used in many applications in the analysis of gaseous streams. Very little research has been carried out into the introduction of, and subsequent analysis of, liquid samples into a process mass spectrometer. 

Beckmann, K., Messinger, J., Badger, M.R., Wydrzynski, T, Hillier, W. (2009) Online Mass Spectrometry Membrane Inlet Sampling. Photosynth. Res. 102 511 -522. 

Fierro S, Nagel T, Baltruschat H, Comninellis C (2008) Investigation of formic acid oxidation on Ti/lT02 electrodes using isotope labeling and online mass spectrometry. Electrochem Solid-State Lett 11 E20-E23... 

Dolch ME, Frey L, Homuss C, et al. Molecular breath-gas analysis by online mass spectrometry in mechanically ventilated patients a new software-based method of COj-controlled alveolar gas monitoring. J Breath Res. 2008 2 037010 10. 

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