Lignin mass spectroscopy

Meier, D., and Faix, O., 1992, Pyrolysis-gas chromatography-mass spectroscopy, in Methods in Lignin Chemistry, S. Y. Lin and C. W. Dence, eds., Springer-Verlag, Berlin, pp. 177-199. 

The presence of multiple types of chemical bonds in CDOM dictates its overall absorbance. Because CDOM is a heterogeneous mixture of perhaps hundreds or thousands of different compounds it is impossible to identify which of them is most responsible for the CDOM absorbance. However, several investigators have begun to use spectrophotometry and mass spectroscopy to identify individual chromophores [47-49]. Table 1 describes the maximum absorbance of certain molecular bonds and phenolic compounds that are likely to be present in CDOM derived from terrestrial sources (e.g., lignin) [12,50,51]. 

These examples show the utility of using C NMR spectroscopy, dissolved lignin, and stable isotopes as molecular tracers of photodegradation of CDOM. Other tools of mass spectroscopy and compound separation and identification should provide additional information on changes to DOM as it is photodeg-raded. Recently, several groups have presented spectroscopic and spec-trophotometric methods for identification of chromophores [47-49,131]. 

Lapierre, C., Pollet, B., Monties, B., and Rolando, C. (1991) Thioacidolysis of spruce lignin Gas chromatography-mass spectroscopy analysis of the main dimers recovered after Raney nickel desulfurization. Holzforschung 45(1), 61-68. 

Jakab, E Faix, 0 and Till, F. (1997). Thermal decermposition of milled wood lignins studied by thermogravimetry/mass spectroscopy. /. Anal. Appl. Pyroly. 40-41, 171 - 186. 

Microbial transformations of DOM were also studied by incubation experiments. The DOM extracted from maize straw and forest floors was incubated for 90 days and samples taken before and after incubation were analyzed by Py-FIMS and complementary UV absorbance, fluorescence emission spectroscopy, FTIR-spectroscopy, 1H NMR spectroscopy, and 13C natural abundance (Kalbitz et al., 2003). The Py-FI mass spectra showed increases in the proportions of phenols and lignin monomers at the expense of lignin dimers and alkylaromatics during... 

Difference spectroscopy has been useful in interpreting the UV-visible spectra of lignins. In this technique, the absorption spectrum measured before a given chemical treatment is subtracted from that recorded after the treatment (or vice versa). In the simplest case, a compound, C, is transformed to a product P. At any time during the reaction, these quantities are related by mass balance. Equation 3.4, where Cq is the initial concentration of C. The difference in... 

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