Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Humic materials analytic techniques

To further understand the molecular organization in humic systems at the level of covalent and noncovalent interactions, additional developments in the high-resolution analytical tools are needed. To achieve this level of resolution, techniques used to explore the complexity of humic materials must be coupled to separation methods that facilitate substantial reductions in the molecular heterogeneity of studied systems. [Pg.491]

The reviewed results showed that online coupling of separation techniques to multiple analytical detectors can provide the most powerful tools for exploring multidimensional chemical space of NOM and HS. The huge potential of applying this approach to unfolding molecular complexity of natural materials is best of all demonstrated by the results of offline characterization of the fractionated humic materials which are discussed below. [Pg.518]

The transformation of plant detritus into stabilized humic substances is one of the most complex and least understood biogeochemical processes in the carbon cycle (Stevenson, 1994). Traditionally, decomposition and humification of plant residues was thought to be dominated by the mineralization of labile materials, while more recalcitrant aromatic compounds accumulate in the soil. The application of modem analytical techniques—including solid-state NMR spectroscopy, pyrolysis gas chromatography, and degradative chemical techniques—to the study of decomposition and humification has significantly altered this simple view of carbon transformation in the soil (Baldock et al., 1997 Kogel-Knabner, 1997). [Pg.4145]

As yet, no single analytical method, degradative or instrumental, can provide data for absolute characterization of the structure of humic materials. Therefore, a combination of several techniques, with comparison and confirmation of results from each method, must be used to unravel the complex issues of humic composition and properties. [Pg.12]

Used widely in synthetic macromolecular and natural biopolymer fields to evaluate structural and thermodynamic properties of macromolecular materials, thermal analytical methods have been applied to assist in the characterization of natural organic matter (NOM). Originally applied to whole soils, early thermal studies focused on qualitative and quantitative examination of soil constituents. Information derived from such analyses included water, organic matter, and mineral contents (Matejka, 1922 Tan and Hajek, 1977), composition of organic matter (Tan and Clark, 1969), and type of minerals (Matejka, 1922 Hendricks and Alexander, 1940). Additional early studies applied thermal analyses in a focused effort for NOM characterization, including structure (Turner and Schnitzer, 1962 Ishiwata, 1969) and NOM-metal complexes (e.g., Schnitzer and Kodama, 1972 Jambu et al., 1975a,b Tan, 1978). Summaries of early thermal analytical methods for soils and humic substances may be found in Tan and Hajek (1977) and Schnitzer (1972), respectively, while more current reviews of thermal techniques are provided by Senesi and Lof-fredo (1999) and Barros et al. (2006). [Pg.784]

The Karl Fischer water determination is a widely used technique in analytical chemistry (Kolthoff and Elving, 1961 Mitchell and Smith, 1980) and has been successfully used on many complex materials such as carbohydrates and whole grains (Mitchell and Smith, 1980). The method works well on other complex organic substances and it may work well on humic substances. [Pg.454]


See other pages where Humic materials analytic techniques is mentioned: [Pg.181]    [Pg.500]    [Pg.513]    [Pg.518]    [Pg.808]    [Pg.815]    [Pg.179]    [Pg.38]    [Pg.57]    [Pg.195]    [Pg.139]    [Pg.11]    [Pg.533]    [Pg.489]    [Pg.10]    [Pg.288]    [Pg.951]    [Pg.1168]    [Pg.573]   


SEARCH



Analytical techniques

Humic materials

© 2024 chempedia.info