Mass spectroscopic technique

Mass spectroscopy is a useful technique for the characterization of dendrimers because it can be used to determine relative molar mass. Also, from the fragmentation pattern, the details of the monomer assembly in the branches can be confirmed. A variety of mass spectroscopic techniques have been used for this, including electron impact, fast atom bombardment and matrix-assisted laser desorption ionization (MALDI) mass spectroscopy. 

Kohse-Hoinghaus, K. et al., Combination of laser- and mass-spectroscopic techniques for the investigation of fuel-rich flames, Z. Phys. Chem., 219, 583, 2005. 

Recently the proposed Oz evolution mechanism was supported by the results of a DEMS (Differential Electrochemical Mass Spectrometry) study performed by Wohlfahrt-Mehrens and Heitbaum [71] on Ru electrodes. Using this mass spectroscopic technique and lsO labeling for the determination of reaction products during 02 evolution, it could be verified that the oxygen of the oxide formed on Ru takes part in the 02 evolution process. The same observation was made for Ru02 electrodes when using labeled H2lsO. 

The development of mass spectroscopic techniques such as matrix assisted laser desorption (MALDI) and electrospray mass spectrometry has allowed the absolute determination of dendrimer perfection [7,8], For divergent dendrimers such as PAMAM and PPI, single flaws in the chemical structure can be measured as a function of generation to genealogically define an unreacted site of or a side reaction producing a loop at a particular generation level. Mass spectromet-ric results on dendrimers, not only demonstrate the extreme sensitivity of the technique, but also demonstrate the uniformity of the molecular mass. The polydispersity index of Mw/Mn for a G6 PAMAM dendrimer can be 1.0006 which is substantially narrower than that of living polymers of the same molecular mass [7],... 

Mass-spectroscopic technique has also been used with non-fissile targets after pile or cyclotron bombardment to determine the mass-numbers of radioactive nuclides. In one case, the branching ratios of certain isotopes for and electron capture decay (where different elements are produced by the two routes) were determined from the amount of the stable end-products of radioactive decay, using the mass-spectrometer to identify the isotopes concerned and to correct for any stable impurities of the elements concerned (98). For some purposes, mass-spectroscopic separations could be very valuable technically such as the... 

Bonaldi, T., Imhof, A. and Regula, J.T. (2004) A combination of different mass spectroscopic techniques for the analysis of dynamic changes of histone modifications. Proteomics, 4, 1382—1396. 

Within a few years this result was extended to room-temperature studies by several investigators. Kistiakowsky and Volpi253 used mass-spectroscopic techniques to obtain a room-temperature value of k71 = A74, 74A 75 = 4.6 x 1010 M 2 sec-1, where the process they envisaged was... 

Although neither NIR nor mass spectroscopic techniques are likely to be used to measure 02 only, they can be justified to simultaneously measure 02 and a multiplicity of other components in a sample. 

Other detection methods. Besides XPS, other chemically sensitive techniques are available to probe the reaction. Surface reflection absorption infrared spectroscopy [130] and electron-energy loss spectroscopy [131] give detailed information on the vibrational states and thus the bonds of surface species. Gas-phase mass spectroscopic techniques provide information about the desorbing species. 

The reaction of mam-porphyrin IX diethyl ester with [Ir(Cl)(CO)3]2 or [Ir(Cl)(CO)(cot)2] yields the iridium(III) porphyrin derivative [Ir(CO)(HePDEE)] (HePDEE = hematoporphyrin diethyl ester).457 This complex, along with the dimethyl ester derivative, has been characterized by electronic, IR, electron spin resonance and mass spectroscopic techniques as well as magnetic susceptibility measurements. The iridium complexes differ from their rhodium analogues in that they retain a CO ligand in the coordination shell. 

Carbamoylpyrazine in dogs and humans is hydrolyzed to 2-carboxypyrazine and then converted to 2-carboxy-5-hydroxypyrazine (1400) and a combined gas chromatographic-mass spectroscopic technique has been described for the simultaneous determination of 2-carbamoylpyrazine, 2-carboxypyrazine, and 2-carboxy-... 

Numerous potentiometric titration-based chemical models have been proposed, a small number of which has been verified by H, and Al NMR and electrospray mass spectroscopic techniques. The models range in character relative to the number and nature of species considered, from simple (a small number of mononuclear monocitrate species) to inordinately complex (several mono- to trinuclear and mono- to tricitrate species). The models are incongruous, in that no two models are composed of the same species, nor do they predict similar Fe(III)-or Al-citrate aqueous speciation. Similarly, the models differ relative to the predicted impact of citrate on the solubility of Fe(III)- or Al-bearing accessory minerals. 

Craig et al used mass spectroscopic techniques to investigate the fate of trimethylstibine when exposed to ambient oxygen. These authors showed that when trimethylstibine was allowed to oxidize, species containing one to five (Me)3SbO molecules chemically bonded together are produced in aqueous solution (Figure 10) dimethylantimony species were not detected under the experimental conditions used. 

The use of gas-liquid chromatographic and mass-spectroscopic techniques in combination have greatly facilitated the separation and identification of fragments from 0-methylated dextrans. For detailed descriptions of these procedures, the reader is referred to a series of papers by Lindberg and associates. ... 

The most stable structure of a particular cluster is often closely related to the structures of clusters of a similar number of atoms, and it is not surprising that the vibrational properties also show relatively smooth changes with changing cluster size. The difficulty of identifying individual clusters by their vibrations alone can be avoided if the clusters can be separated according to their masses, and recent advances in mass spectroscopic techniques have been very important for the study of cluster structures. Mass separation is, of course, usually performed on charged systems. 

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