Molecular characterizations organic matter

Murae T. (1995) Characterization of extraterrestrial high-molecular-weight organic-matter by pyrolysis-gas chromatography mass-spectrometry. J. Anal. Appl. Pyrol. 32,65 -73. 

The fate of organic matter in the marine environment is largely related to its molecular structure, as this determines chemical reactivity. Compoimds characterized by high concentrations in seawater and the sediments typically have slow loss rates relative to their production. These compounds tend to exhibit low chemical reactivity in the marine environment and can persist in seawater fiar thousands of years. Conversely, compounds with low concentrations typically have high loss rates relative to their production. Their high reactivity is generally due to rapid biotic uptake and transformation, leading to turnover times that are on the order of minutes to days. Thus, to imderstand... 

Marine chemists have had limited success in characterizing the molecular structure of organic matter, particularly for the dissolved compounds. Chemical analysis usually starts with the isolation of POM from DOM using a filter with a 0.2-p,m pore size. This is generally followed by elemental analysis. More sophisticated approaches involve structural analysis, but this is usually limited to detection of functional groups or broad classes of compounds. 

Recent investigations provide new insight on the structural chemistry of dissolved organic matter (DOM) in freshwater environments and the role of these structures in contaminant binding. Molecular models of DOM derived from allochthonous and autochthonous sources show that short-chain, branched, and alicyclic structures are terminated by carboxyl or methyl groups in DOM from both sources. Allochthonous DOM, however, had aromatic structures indicative of tannin and lignin residues, whereas the autochthonous DOM was characterized by aliphatic alicyclic structures indicative of lipid hydrocarbons as the source. DOM isolated from different morphoclimatic regions had minor structural differences. 

Sleighter, R. L., and Hatcher, P. G. (2007). The application of electrospray ionisation coupled to ultrahigh resolution mass spectrometry for the molecular characterization of natural organic matter. I. Mass Spectrom. 42, 559-574. 

Tremblay, L. B., Dittmar,T., Marshall, A. G., Cooper, W. J., and Cooper, W.T. (2007). Molecular characterization of dissolved organic matter in a North Brazilian mangrove porewater and mangrove-fringed estuaries by ultrahigh resolution Fourier transform-ion cyclotron resonance mass spectrometry and excitation/emission spectroscopy. Marine Chem. 105, 15-29. 

Electrophoresis plays a key role as an analytical or preparative technique in the characterization of natural organic matter because it gives information about the behavior of these molecular mixtures in controlled solution conditions, depending on both the size and the charge distribution frequency of the analytes in the complex mixture. Historically, the first electrophoretic separations were conducted with environmental colloids and over the years all the techniques based on zone, gel electrophoresis, or isoelectric focusing were used in their different setups to analyze natural organic matter and environmental particles to a minor extent. The goal of... 

The intention of this chapter was to review advances in analytical pyrolysis and soft ionization mass spectrometric techniques as applied to the molecular-chemical characterization of nonliving organic matter. 

Leinweber, R, Jordan, E., and Schulten, H.-R. (1996). Molecular characterization of soil organic matter in pleistocene moraines from the Bolivian Andes. Geoderma 72,133-148. 

Repeta, D. J., Quan,T. M., Aluwihare, L. I., and Accardi, A. M. (2002). Chemical characterization of high molecular weight dissolved organic matter in fresh and marine waters. Geochim. Cosmochim. Acta 66, 955-962. 

Characterization of Organically Bound Sulfur in High-Molecular-Weight, Sedimentary Organic Matter Using Flash Pyrolysis and Raney Ni Desulfurization... 

Due to the complexity of organic matter sources in estuaries and the aforementioned problems associated with making only bulk measurements to constrain them, the application of chemical biomarkers has become widespread in estuarine research (see review, Bianchi and Canuel, 2001). The term biomarker molecule has recently been defined by Meyers (2003, p. 262) as compounds that characterize certain biotic sources and that retain their source information after burial in sediments, even after some alteration. This molecular information is more specific and sensitive than bulk elemental and isotopic techniques in characterizing sources of organic matter, and further allows for identification of multiple sources (Meyers, 1997, 2003). 

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