Analytical pyrolysis combined with gas chromatography and mass spectrometry (Py-GC–MS) is a relatively rapid (1–3h) method for the investigation of polymers. Various wood tissues from transgenic poplar clones and from control samples have been subjected to a screening test by Py-GC–MS. Pyrolysis products from lignin- and carbohydrate-derived pyrolysis products were subjected to multivariate principal component analysis (PCA). The first three PC accounting for 39–72% of the total variance in the original data set could be attributed to vinyl products from lignin and levoglucosan from cellulose. Samples with gene construct rbcs-rol C were only discriminated by plotting PC1 versus PC3 using the whole data set. However, the wood from trees containing gene construct 35 S-rol C were discriminated in all examined models indicating significant impacts during biosynthesis of the wood. One sample within the data set was further clustered because it turned out that this tree died off after two vegetation periods.

Two milled wood lignins (MWLs) were isolated from tobacco leaves (laminae) and midrib material according to the Björkman procedure. Prior to MWL isolation, the material was extracted with cyclohexane/ethanol and hot water to remove extractives which could interfere with this isolation. MWLs were obtained with a yield of 0.03% (leaves) and 0.06% (midribs) based on dry pre-extracted material. FT-IR spectroscopy was used for quality control and classification of the isolates. Both preparations fulfilled the spectroscopic lignin criteria of a GS lignin with low syringyl content, although the isolates were not pure. Besides carbohydrate impurities, the lamina material, especially, was contaminated with nitrogen and fatty acid-containing substances. Proteins and cutin are discussed as probable contaminants. Both MWLs were characterized with quantitative pyrolysis—gas chromatography using a resistant heating instrument. Curie-point pyrolysis—gas chromatography/mass spectrometry and pyrolysis—mass spectrometry were used for additional characterization of yboth MWL samples. The results show that the tobacco MWL contains up to 22% carbohydrate-type impurities. Small amounts of alkaloids, proteins and lipids were also detected as contamination. Results of previous studies on mineral acid residues could be corroborated: tobacco lignin contains approximately 10% 4-hydroxyphenylpropane, 78–82% guaiacylpropane and 10–13% syringylpropane moieties.

Thermal degradation products of woods arising at 450°C have been separated by gas chromatography on a DB-1701 capillary column. GC retention times and mass spectral data of 104 polysaccharide derived pyrolysis products are tabulated. The elemental composition of 76 identified compounds are also presented. The mass spectra were obtained by electron impact ionization (EI). However, the molecular mass of all degradation products with Mw>76 was determined by chemical ionization (CI) using iso-butane as reagent gas. The peak assignment was proved in 38 cases by mass spectrometry of authentic compounds and 32 degradation products were identified according to the literature. The spectral data are presented as a Mass Peak Index showing the intensity of the nine most abundant peaks.

Thermal degradation of ω-guaiacoxy-acetoguaiacone-benzylether (A) and ω-syringoxy-acetoguaiacone-benzylether (B) has been investigated for a better understanding of the thermolytic behaviour of lignins. Earlier differential scanning calorimetric studies revealed that degradation starts below 200° C. Direct insertion probe experiments also demonstrated that splitting of linkages between aroxy and acetoguaiacone-benzylether (C) moieties commences at 175° C. As a consequence the presence of the following compounds was observed: guaiacol and C (from A) and syringol and C (from B). Simultaneously to these splitting mechanisms a rearrangement occurs between the ω-carbon of compound C and the phenolic oxygen of the aroxy residues, resulting in the formation of 2-methoxybenzaldehyde and acetovanillone-benzylether (from A) and 2,6-dimethoxybenzaldehyde and acetovanillone-benzylether (from B). Pyrolysis-gas chromatography-mass spectrometry experiments between 240 to 600°C corroborated these results. The higher the pyrolysis temperature the more peaks are displayed in the pyrograms. The pyrograms obtained at 600° C show 40 to 70 major peaks which were evaluated. The relative retention times, M+ values and in most cases the assignments to defined compounds are given. Many ‘unknown’ substances could be identified as condensation products derived from benzyl radicals. Flow diagrams illustrate the main splitting mechanisms of compounds A and B.