Speciation molecular

Infrared spectroscopy has broad appHcations for sensitive molecular speciation. Infrared frequencies depend on the masses of the atoms iavolved ia the various vibrational motions, and on the force constants and geometry of the bonds connecting them band shapes are determined by the rotational stmcture and hence by the molecular symmetry and moments of iaertia. The rovibrational spectmm of a gas thus provides direct molecular stmctural information, resulting ia very high specificity. The vibrational spectmm of any molecule is unique, except for those of optical isomers. Every molecule, except homonuclear diatomics such as O2, N2, and the halogens, has at least one vibrational absorption ia the iafrared. Several texts treat iafrared iastmmentation and techniques (22,36—38) and thek appHcations (39—42). 

Molecular solutions, 8 697 Molecular speciation/quantification, infrared spectroscopy in, 23 140 Molecular spectroscopy, 10 508 Molecular structure. See also Chemical structures Molecular formulas of linear low density polyethylene, 20 182-184... 

Being the third most common element (after carbon and hydrogen) in petroleum product, sulfur has been analyzed extensively. Analytical methods range from elemental analyses to functional group (sulfur-type) analyses to structural characterization to molecular speciation (Speight, 2001). Of the methods specified for the... 

Liang, Z. Hsu, C.S. Molecular Speciation of Saturates by Online Liquid Chromatography-Field Ionization Mass Spectrometry. Energy Fuels 1998, 72, 637-643. 

Forstner, H. J. L., R. C. Flagan, and J. H. Seinfeld, Molecular Speciation of Secondary Organic Aerosol from Photooxidation of the Higher Alkenes 1-Octene and 1-Decene, Atmos. Environ., 31, 1953-1964 (1997a). 

Regarding the liquid/liquid extraction from the metal standpoint is rather different. This is the classical approach of coordination chemistry (most of the publications in this area). Today, it is still difficult to establish a direct link between the two descriptions of the organic extractant phases. To better understand liquid/ liquid extraction, the aggregation number and coordination number must be measured separately for each system and set of initial conditions. This is the only way to determine the role of the aggregates in the extraction efficiency. This important point was emphasized by Yaita et al. (61). In this way, Gannaz et al. has used an approach combining studies on both supramolecular and molecular speciation of extractant systems of the DIAMEX-SANEX process (36). 

This paper will survey the current status of surface analysis in the examination of chemically modified electrode surfaces. In doing so, we shall take selected examples from our laboratory and the literature to illustrate some of the methods that have been employed to answer questions about surface topography, atomic and molecular speciation, and molecular orientation and bonding. 

A primitive approach to molecular speciation involves identification of the molecular functionalities through the binding energies (BE s) of their constituent elements. This approach has been used to identify electropolymerized poly-pyrrole (9) and N-(0-hydroxybenzyl)anillne/tyrosine (84) films. In the latter case the identification was confirmed with multi-reflection IR spectroscopy. Both examples used either monomers or model compounds as references to generate known comparison spectra. The BE s and peak shapes have also been used to identify the presence of the ferricinium ion on freshly prepared surfaces (85). In this way the identification is similar to fingerprinting. 

The principal difficulty with the previous approaches to molecular speciation has been less with what was attempted and more with the inability to control the sample surface. A recent study of RF plasma treated surfaces has shown that the surface composition can change on exposure to laboratory air and water vapor (91,92). The development of a sample isolation/ treatment/... 

Forstner, H.L., R.C. Flagan, and J.H. Seinfeld. 1997. Molecular speciation of secondary organic aerosol from photooxidation of higher alkenes 1-octene and 1-decene. Atmos. Environ. 31 1953-1964. 

Spectroscopic techniques have received increased attention for the study of natural organic matter (NOM) over the past decades (Hatcher et al., 2001 Abbt-Braun et al., 2004). Such techniques allow the determination of molecular speciation in many cases without the need for extractions, derivatization, or hydrolysis. Spectroscopy is generally less selective in nature than for example chemical extraction techniques, even of chemically or thermally recalcitrant compounds (Frimmel et al., 2002 Haberstroh et al., 2006), though important restrictions for specific bonds apply for some spectroscopic techniques. Equally important are the potentials to investigate the spatial relationships between NOM and mineral phases, surface properties and alteration, and micro-scale heterogeneity within NOM. With improved capabilities and access to synchrotron facilities, worldwide efforts in applying an entire range of powerful spectroscopic tools have proliferated in all areas of science. 

In this chapter, we shall introduce soil speciation concepts by consideration of inorganic trace elements in dissolved and adsorbed forms, with reference to both their molecular speciation and their operationally defined soil component speciation. We shall then consider the implications of chemical speciation in soils for agriculture and soil pollution. 

Since its inception about 15 year ago, MALDI-IMS has been developed into a powerful and versatile tool for biomedical research. It allows for the investigation of the spatial distribution of molecules at complex surfaces. The combination of molecular speciation with local analysis makes a chemical microscope that can be used for the direct biomolecular characterization of histological tissue section surface. However, successful detection of the analytes of interest at the desired spatial resolution requires careful attention to several steps in the IMS protocol matrix selection, matrix coating, data acquisition, and data processing. MALDI-IMS is increasingly playing an important role in the drug discovery and development and disease treatment. 

The interaction of radiation with matter can have profound effects. Whether in solid, solution, or gaseous states, radioactivity can impact the environment and therefore change the molecular speciation of the actinides. To put this into perspective, three examples are discussed below plutonium metal, americium crystals, and an aqueous solution of plutonium. 

Regardless of the t)q)e of soluble metal silicates used, they are subject to the same molecular speciation in aqueous solution resulting in a mixture of monomeric tetrahedral ions, oligomeric linear or cyclic silicate ions, and polysilicate ions. Sodium metasilicate, an example of a soluble metal silicate, can be prepared in anhydrous form or in the presence of water of crystallization as the penta- or nona-hydrate. It is readily soluble in water [8]. 

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