Thermochemolysis with

Vane, C. H. (2003). The molecular composition of lignin in spruce decayed by white-rot fungu (Phanerochaete chrysosporium and Trametesw versicolour) using pyrolysis GC-MS and thermochemolysis with tetramethylammonium hydroxide. Int. Biodeter. Biodegr. 51, 67-75. 

Clifford, D.J., Carson, D.M., McKinney, D.E., Bortiatynski, J.M., and Hatcher, P.G. (1995) A new rapid technique for the characterization of lignin in vascular plants thermochemolysis with tetramethylammonium hydroxide (TMAH). Org. Geochem. 23, 169-175. 

Hatcher, P.G., Nanny, M.A., Minard, R.D., Dible, S.C., and Carson, D.M. (1995) Comparisons of two thermochemolytic methods for the analysis of lignin in decomposing wood The CuO oxidation method and the method of thermochemolysis with TMAH. Org. Geochem. 23, 881-888. 

Structural Characterization of Humic Substances Using Thermochemolysis with Tetramethylammonium Hydroxide... 

Tanezos, I., Rendl, K., and Schmidt, H., The behavior of aldehydes-produced as primary pryrolysis products-in the thermochemolysis with tetramethylammonium hydroxide, J. Anal. Appl. Pyrolysis, 49, 319-327, 1999. 

As noted above, the use of TMAH/thermochemolysis for the structural characterization of different humic materials have been applied in two different forms pyrolysis of the humic materials in the presence of TMAH or a confined reaction of the humic materials with the TMAH in a sealed glass ampoule at lower temperatures. Both methods release the same types of compunds. 

Pyrolysis in the Presence of TMAH. A wide set of Fulvic Acids (FA), Humic Acids (HA) and related materials from different origins have been thus far studied using the TMAH/thermochemolysis procedure (9,15-17,22,24,25). The TMAH procedure has mainly been performed in pyroprobe units, in much the same way as the conventional flash pyrolysis using either quartz tubes and/or a platinum coil, by mixing the humic materii with a few drops of the reagent prior to heating. 

The aromatic acids released from different HA upon pyrolysis in the presence of TMAH probably represent original components of the HA structure released by the thermolytic action of TMAH (10,12,16,17). This observation is supported by the TMAH thermochemolysis data of Hatcher et al. (23) and Hatcher and Clifford (16) for a volcanic soil humic acid. In fact, the C-NMR spectrum of this particular HA (shown in Figure 4) clearly indicates that it is composed of only aromatic and carboxyl carbons. Conventional pyrolysis of these HA produced trace quantities of volatile products without the release of any significant compounds while pyrolysis in the presence of TMAH yielded mainly benzenecarboxylic acid methyl esters (Figure 5), in accordance with the NMR data. 

Main Advantages of the TMAH/Thermochemolysis Procedure in Comparison with Other Chemical Degradative and rolysis Methods... 

Derivatization of the sample renders many of these polar pyrolysis products sufficiently volatile for gas chromatographic separation. Thus it is possible to separate and detect many more strucmrally significant products than observed by conventional pyrolysis techniques.The most common of the derivatization processes is a methylation reaction where organic matter is mixed with tetramethylammonium hydroxide (TMAH) prior to pyrolysis. Throughout the literature, several different terms have been employed to describe derivatization reaction and in this chapter the term thermochemolysis will be used. 

In practice, thermochemolysis of organic matter mainly produces esters of aliphatic and aromatic acids, methyl esters of aliphatic alcohols and phenols, and a variety of other methylated derivatization products. " Thermochemolysis is particularly suitable for the analysis of fatty acids associated with organic matter matrix which are evolved as methyl esters when TMAH is employed. 

Off line thermochemolysis is also possible at much lower temperatures (250°C). " Thermochemolysis reactions with TMAH can be conducted in a sealed glass ampoule thus allowing for more controlled conditions, where internal standards can be added to provide quantitative measurement. Off line thermochemolysis gives similar results as the more time consuming chemical degradation methods used in the analysis of organic matter. ... 

Hatcher, P. G. and Minnard, R. D., Comparison of dehydrogenase polymer (DHP) lignin with native lignin from gymnosperm wood by thermochemolysis using TMAH, Org. Geochem., 24, 593-600, 1996. 

Pyrolysis with in situ methylation in the presence of TMAH is now commonly applied for the structural investigation of HS. It has been reported, however, that TMAH not only methylates polar pyrolysate but also assists in bond cleavage. For example, TMAH was found as effective at 300°C as at 700°C for the production of some volatile products from HS, indicating that pyrolysis occurs with equal effectiveness at subpyrolysis temperature of 300°C. It is believed that TMAH pyrolysis is actually a thermally assisted chemolysis rather than pure pyrolysis and it can cause hydrolytic ester and ether bond cleavage even at lower temperature, resulting in some unwanted side reactions, e.g., artificial formation of carboxylic groups from aldehydes. Therefore, TMAH thermochemolysis at low temperature, e.g., 300°C has been proposed. This technique offers several advantages over classical flash pyrolysis or preparative pyrolysis apparatus " ... 

Fatty acid methyl esters are another abundant group of products produced by TMAH thermochemolysis. Under these conditions fatty acids of triacyl-glycerols and other hpids are effectively esterified [97]. But only the saturat-ed/branched fatty acids can be used as reliable biomarkers with this analysis. Unsatuxated fatty acids tend to isomerize and degrade under the strong basic conditions using TMAH and heat [108]. 

To further characterize the products released upon thermochemolysis, comprehensive GC x GC-TOFMS was utilized. Thermochemolysis was performed at 280°C under conditions as described above. GC x GC-TOFMS analysis was performed using an Agilent 6890 GC with a GC X GC modulator (Leco) coupled to a Pegasus IV TOF mass spectrometer (Leco). The GC injector was operated in split mode (20 1) with a column flow rate of 1 mL/min and held at 250°C. GC x GC separation utilized a nonpolar column and a polar column a BPX5 (30 m X 0.25 mm x 0.25 pm SGE) and a BPX50 (1.8 m X 0.1 mm x 0.1 pm SGE), respectively. The GC oven temperature was held for 10 min at 35°C and ramped to 300°C at a rate of 5°C/min and then held for 5 min the second column was ramped at +15°C relative to the first column with a modulation time was 4 s. Mass spectra were acquired in electron ionization mode from 33 to 500 amu with an acquisition rate of 135 Hz. 

Fragmentation of macromolecules can be achieved by coupling thermochemolysis (Py) with GC/MS (Py-GC/ MS), or, more commonly, performing a wet chemical treatment of the sample. Although the analytical procedures are relatively laborious and time-consuming, GC/ MS is still unsurpassed in its capacity to unravel the composition of the archaeological organic materials at a molecular level. Thble 36.2 shows a representative list of applications reported in the literature. 

Tetramethylammonium hydroxide (TMAH) is the most commonly used reagent for THM, and TMAH thermochemolysis has been extensively applied to the characterization of organic natural materials [98,103,104,107,108,124,127,134-138]. Py with TMAH involves the deprotonation of carboxylic acids and the hydrolysis of ester and ether bonds, followed by the formation of tetramethylammonium salts, which are subsequently subjected to thermal dissociation and leads to the formation of the corresponding methyl derivatives. 

Sun, Y.-C., Ko, C.-J. (2006) Combining electrothermal vaporization inductively coupled plasma mass spectrometry with in situ TMAH thermochemolysis for the direct determination of trace impurities in a polymer-based photoresist. J. Anal. At. Spectrom., 21, 311-316. 

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