Mass spectrometry, and hydrogenation

Buijs, J., Vera, C.C., Ayala, E., Steensma, E., Hakansson, P., and Oscarsson, S. (1999) Conformational stability of adsorbed insulin studied with mass spectrometry and hydrogen exchange. Analytical Chemistry, 71, 3219-3225. 

Kraus, M., Janek, K., Bienert, M., Krause, E. (2000) Characterization of intermolecular p-sheet peptides by mass spectrometry and hydrogen isotope exchange. Rapid Commun Mass Spectrom, 14 (13), 1094-1104. 

Cheng, M., Hudson, J., Drinkwater, D., and Nero, V., "Total Olefin in Gasoline Determined by Mass Spectrometry and Hydrogenation, Proceedings, 44th ASMS Conference on Mass Spectrometry and Allied Topics, 1997, Portland, Or on. 

In order to relate material properties with plasma properties, several plasma diagnostic techniques are used. The main techniques for the characterization of silane-hydrogen deposition plasmas are optical spectroscopy, electrostatic probes, mass spectrometry, and ellipsometry [117, 286]. Optical emission spectroscopy (OES) is a noninvasive technique and has been developed for identification of Si, SiH, Si+, and species in the plasma. Active spectroscopy, such as laser induced fluorescence (LIF), also allows for the detection of radicals in the plasma. Mass spectrometry enables the study of ion and radical chemistry in the discharge, either ex situ or in situ. The Langmuir probe technique is simple and very suitable for measuring plasma characteristics in nonreactive plasmas. In case of silane plasma it can be used, but it is difficult. Ellipsometry is used to follow the deposition process in situ. 

Jewell, D.M., Ruberto, R.G., Seshadri, K.S., "Transferable Hydrogen in Coal Liquids An Integrated Approach", presented at the 26th Annual Conference on Mass Spectrometry and Allied Topics", A.S.M.S., St. Louis, M0., May 28, 1978. 

Dramatic advances in mass spectrometry and improvements in the various steps within the experimental hydrogen exchange procedures have resulted in the development of automated systems for high-throughput, high-resolution H/D exchange analysis [6, 8, 40-44]. 

A reevaluation of molecular structure of humic substances based on data obtained primarily from nuclear magnetic resonance spectroscopy, X-ray absorption near-edge structure spectroscopy, electrospray ionization-mass spectrometry, and pyrolysis studies was presented by Sutton and Sposito (2005). The authors consider that humic substances are collections of diverse, relatively low molecular mass components forming dynamic associations stabilized by hydrophobic interactions and hydrogen bonds. These associations are capable of organizing into micellar structures in suitable aqueous environments. Humic components display contrasting molecular motional behavior and may be spatially segregated on a scale of nanometers. Within this new structural context, these components comprise any molecules... 

An interesting question is how H3 is formed on the emitter surface and whether H3 molecules can exist on the surface. This question can be investigated with a measurement of the appearance energy of Hj ions. Jason etal.264 find Hj in field ionization of condensed layers of hydrogen, and measure the appearance energy to be 12.7 eV. This value is 2.9 eV smaller than that of H2. Ernst Block conclude265 from a similar measurement in field ionization mass spectrometry of hydrogen that an H 3 ion is formed at the moment when a chemisorbed H atom combines... 

The important points are that the radicals arc formed adjacent to one another and that they are not free to diffuse throughout the solid crystal. The methane17 and ethane66 analogs of this reaction have been observed by mass spectrometry and have been previously discussed. The driving force is the saturation of the election octet in the primary ion radical by acquisition of a hydrogen atom. 

Marine lipids with their diversity of unsaturated and branched chain acid moieties are a difficult class of materials to analyze. Ruminants (sheep, goats, cows, etc.) have a bacterial "factory" in the rumen which is able to produce branched-chain partially-hydrogenated lipids from ingested plant lipids. These lipids are incorporated into the milk and meat of the animals and eventually into animals which feed upon the ruminants. As a rule animal lipids are highly complex in comparison to plant materials. Although the branched chain materials are usually present in low concentration when compared to the common fatty acid moieties, complete description of these fats requires more sophisticated GC and thus long open tubular columns in tandem with mass spectrometry and computer analysis of the data has become an important approach. Even with a 100-m column, subcutaneous lipids of barley-fed lambs were so complex that prior fractionation with urea adducts was necessary (17). 

Catalytic Experiments. Activities were performed in a 1 liter Parr reactor. A typical experiment was performed as follows at a temperature of 100 °C, 100 mg of the catalyst and 1.5 /. wt of (-)-carvone (Aldrich) in n-hexane solution (100 ml) were Introduced in a high pressure Parr reactor equipped with mechanical stirring and automatic temperature control. Before introducing the hydrogen the system was purged 2 or 3 times with Nz> The total hydrogen pressure was 21 atm. The reaction products were analysed by gas chromatography. NMR and Mass Spectrometry and identified as unreacted carvone, carvotanacetone, carvomenthone and three carvomenthol stereoisomers (axial-equatorial, equatorial-equatorial and equatorial-axial). 

Pan J, Rintala-Dempsey AC, Li Y, Shaw GS, Konermann L. 2006. Folding kinetics of the S100A11 protein dimer studied by time-resolved electrospray mass spectrometry and pulsed hydrogen-deuterium exchange. Biochemistry 45(9) 3005-3013. 

IR spectroscopy is covered in Chapter 13, and hydrogen and carbon NMR spectroscopy are covered in Chapter 14. These topics have been separated to provide a more reasonable chapter size and to increase flexibility in order of presentation. Mass spectrometry and UV-visible spectroscopy are covered in Chapter 15, so these topics can be made optional if desired. 

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