Advances in thermochemolysis: targeted applications in analysis of plant biomaterials

Shadkami, Farzad (2009) Advances in thermochemolysis: targeted applications in analysis of plant biomaterials. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Thermochemolysis (or thermally-assisted hydrolysis/methylation) is a unique in situ technique for analysis of a wide range of biomaterials, in their natural form, from plants material. It involves derivatization of analyte functional groups concurrent with mild thermal fragmentation of biomaterials and selective base-catalyzed cleavage of ester and ether bonds rather than the harsh thermal fragmentation and decomposition which is the case during the traditional pyrolysis. This thesis has targeted a number of special applications, all involving the chemical profiling of complex and different samples using trimethylsulfonium hydroxide (TMSH). Application of thermochemolysis-TMSH for the chemical profiling of needles of ozone fumigated pine trees showed that the concentrations of 3-hydroxybenzoic and 3,4-dihydroxybenzoic acids, useful as ozone damage markers, decreased with increased ozone dosage. It also revealed that the resin acids, anticopalic, 3-oxoanticopalic, 3β-hydroxyanticopalic and 3,4-cycloanticopalic acid were prominent in the ozone-sensitive pine; however, only anticopalic acid was present in the ozone-tolerant clone. In another application, the chemistry of the antioxidant catechin was investigated under thermochemolysis conditions wherein both fully and partially methylated catechin in addition to a base-catalyzed epimerization product (i.e. methylated epicatechin) were identified. The polymeric structures of catechin-containing condensed tannins were also examined by thermochemolysis. A novel two-step methylation technique (TMS-diazomethane followed by thermochemolysis) was developed which allowed for the observation, for the first time, of a dimeric catechin at MW = 540 amu. -- A direct thermochemolysis solids injector device was constructed allowing the use of an injection port (instead of a pyrolyzer) for thermochemolysis-gas chromatography/mass spectrometry. The analytical usefulness of this thermochemolysis device was tested in direct comparison to a microfurnace pyrolyzer. It exhibited a similar chromatographic result for the thermochemolysis of standard catechin. Further, it was shown that this solids injector was suitable for real sample analysis containing a wide range of compounds including small phenolics, fatty acids, diterpene resin acids and flavonoids. In addition, chemical analysis of lignin macromolecules was investigated using the same direct thermochemolysis solids injector. This research work was the first to observe new dimeric thermochemolysis products (sylvatesmin and yangambin). These two lignin markers can be used to differentiate hardwood lignins from softwood lignins.

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