Chemical pretreatment techniques

The stable free radicals in coal can adversely affect the 13C signal intensity. However, the quantitative reliability of the method can be greatly improved by prior treatment of coal with chemicals such as samarium(II) iodide (Stock et al., 1988) to selectively reduce the organic free radicals. Thus, this potential error that has influenced the quantitative aspects of the method can be reduced by the use of a novel pretreatment technique as well as an appropriate standard for measurement of chemical shifts. 

Table 8.7 Chemical RO pretreatment techniques and the species each technique treat.

Native cellulose are commonly modified by physical, chemical, enzymic, or genetic means in order to obtain specific functional properties, and to improve some of the inherent properties that limit their utility in certain application. Physical/surface modification of cellulose are performed in order to clean the fiber surface, chemically modify the surface, stop the moisture absorption process, and increase the surface roughness. " Among the various pretreatment techniques, silylation, mercerization, peroxide, benzoylation, graft copolymerization, and bacterial cellulose treatment are the best methods for surface modification of natural fibers. 

Ragauskas, A. J., Huang, F. Chemical pretreatment techniques for biofuels and biorefineries from softwood. In Pretreatment Techniques for Biofuels and Biorefineries, Fang, Z. (Ed ), Springer New York, 2013,151-179. 

In 1996, Ciitchlow and Brewis" conducted an extensive review of 41 mechanical, chemical, electrochemical, or other identified treatments specifically designed to modify the surface of aluminum to enhance bond durability. They listed a number of useful conclusions that indicate the direction for future research into these aluminum pretreatment techniques. 

Pretreatment of the collected particulate matter may be required for chemical analysis. Pretreatment generally involves extraction of the particulate matter into a liquid. The solution may be further treated to transform the material into a form suitable for analysis. Trace metals may be determined by atomic absorption spectroscopy (AA), emission spectroscopy, polarogra-phy, and anodic stripping voltammetry. Analysis of anions is possible by colorimetric techniques and ion chromatography. Sulfate (S04 ), sulfite (SO-, ), nitrate (NO3 ), chloride Cl ), and fluoride (F ) may be determined by ion chromatography (15). 

Standard analytical techniques for sampling and pretreatment and analytical requirements for sediment studies are less available than for water and soil studies. To obtain meaningful results from laboratory experiments, the sediment samples should be kept in the original aqueous matrix, and analyses should be carried out immediately to minimize changes to the sample matrix due to chemical and biological processes that could occur during storage. 

Furthermore, the major disadvantages encountered in GC/MS, i.e. undetectability of synthetic polymers and unpredictable interferences due to their presence, may be avoided using the Py-GC/MS technique. All these aspects strongly suggest how useful, and in some cases fundamental, analytical pyrolysis is in the analysis of complex samples, such as those collected from works of art, to implement and support results obtained with wet chemical pretreatment followed by GC/MS analysis. 

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