Flash Pyrolysis-gas Chromatography-mass Spectrometry Research Articles

Transformation of Cyanobacterial Biomolecules by Iron Oxides During Flash Pyrolysis: Implications for Mars Life-Detection Missions.

Answering the question of whether life ever existed on Mars is a key goal of both NASA's and ESA's imminent Mars rover missions. The obfuscatory effects of oxidizing salts, such as perchlorates and sulfates, on organic matter during thermal decomposition analysis techniques are well established. Less well studied are the transformative effects of iron oxides and (oxy)hydroxides, which are present in great abundances in the martian regolith. We examined the products of flash pyrolysis-gas chromatography-mass spectrometry (a technique analogous to the thermal techniques employed by past, current, and future landed Mars missions) which form when the cyanobacteria Arthrospira platensis are heated in the presence of a variety of Mars-relevant iron-bearing minerals. We found that iron oxides/(oxy)hydroxides have transformative effects on the pyrolytic products of cyanobacterial biomolecules. Both the abundance and variety of molecular species detected were decreased as iron substrates transformed biomolecules, by both oxidative and reductive processes, into lower fidelity alkanes, aromatic and aryl-bonded hydrocarbons. Despite the loss of fidelity, a suite that contains mid-length alkanes and polyaromatic hydrocarbons and/or aryl-bonded molecules in iron-rich samples subjected to pyrolysis may allude to the transformation of cyanobacterially derived mid-long chain length fatty acids (particularly unsaturated fatty acids) originally present in the sample. Hematite was found to be the iron oxide with the lowest transformation potential, and because this iron oxide has a high affinity for codeposition of organic matter and preservation over geological timescales, sampling at Mars should target sediments/strata that have undergone a diagenetic history encouraging the dehydration, dihydroxylation, and oxidation of more reactive iron-bearing phases to hematite by looking for (mineralogical) evidence of the activity of oxidizing, acidic/neutral, and either hot or long-lived fluids.

Kinetics of oil generation from brackish-lacustrine source rocks in the southern Bohai Sea, East China

Oil generation (C14+ hydrocarbons) of three Type II kerogen samples isolated from brackish-lacustrine mudstones from Palaeogene strata (Ed3, Es1, Es3) in the southern Bohai Sea was simulated by closed-system gold tube experiments. In addition, a series of complementary analyses (Rock-Eval pyrolysis, total organic carbon, vitrinite reflectance, trace element, X-ray diffraction and flash pyrolysis-gas chromatography–mass spectrometry) were also performed to identify the bulk geochemistry, palaeo-environment and chemical composition of the kerogen. The aim of this study was to achieve a better understanding of the kinetics of oil generation from lacustrine source rocks in the southern Bohai Sea. The results show that the three samples are Type II source rocks deposited in similar palaeo-environments (hot and arid climates, anoxic conditions, and brackish water in shallow to semi-deep lakes) with consequent similarity in the chemical compositions of their kerogens. The organic matter inputs are predominantly composed of lacustrine microalgae, with a relatively small contribution from land plants. The activation energies of oil generation from these samples show a range of 44–52 kcal/mol, with a frequency factor varying from 1.116 × 1014 to 1.274 × 1014 s−1. Due to the similar palaeo-environments and chemical composition, samples in this study exhibit strong consistencies in kinetic parameters. Transformation ratio (TR) evolution curves of oil generation from the three samples, calculated under a linear heating rate (3 K/Ma), exhibit a slight difference, which varies within 4 °C at a given TR. Due to the great similarities of the three kinetic models, an average kinetic model for the Type II brackish-lacustrine source rocks in the southern Bohai Sea was established. This model integrates the characteristics of the three kinetic models and is still dominated by activation energy of 52 kcal/mol. The geological temperature of the oil generation phase for the average model in the southern Bohai Sea is from 92 to 137 °C.

Experimental and dynamics simulation studies of the molecular modeling and reactivity of the Yaojie oil shale kerogen

In this study, the chemical structural parameters of a kerogen from Yaojie oil shale were identified and investigated by using experimental data obtained from solid-state 13C nuclear magnetic resonance spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, flash pyrolysis–gas chromatography–mass spectrometry, and Fourier transform infrared spectroscopy. Twelve constitutional isomers of the Yaojie 2D models with different grids and their corresponding 3D models were constructed by the combination of molecular simulation methods and multiple testing techniques. Finally, a reasonable 3D model of Yaojie kerogen was determined by a series of anneal dynamics simulations and geometry optimization calculations. From the results obtained by Mulliken population analysis and electron density analysis, the π–π conjugation effect among the aromatic ring structures is significantly impacted by the heteroatoms, leading to the accumulation of electrons on heteroatoms. Meanwhile, sulfur, oxygen, and nitrogen in the heterocyclic structures exhibited higher electronic charge density and considerably more reactivity compared with those of other atoms. Moreover, the molecular orbitals of HOMO and LUMO were calculated to examine the properties of chemical reaction of kerogen. The HOMO–LUMO energy gap indicated that the Yaojie kerogen exhibited higher reactivities compared to Type Ⅰ kerogen.

Structural characterization of suberan isolated from river birch (Betula nigra) bark

Suberan is a biopolymer located in the periderm (cork) of above ground parts of plants or the endoderm of roots. It acts as a protective barrier between plants and the environment and is commonly associated with another suberinic biopolymer, suberin. The structure of suberan has not been suggested, but is believed to have structural components similar to suberin. With the use of destructive and non-destructive techniques, including Fourier transform infrared (FTIR) spectroscopy, flash pyrolysis–gas chromatography–mass spectrometry (py–GC–MS), one and two-dimensional high-resolution magic angle spinning (HRMAS) nuclear magnetic resonance (NMR) spectroscopy, the structure of suberan from the Betula nigra bark, is now described. Based on data obtained from B. nigra bark, the non-saponifiable residue, considered to be suberan, is a polymethylenic biopolymer with alkyl chain length consisting mainly of 22 carbons, which is consistent with previous degradative studies. Furthermore, esters, acids and primary alcohols were also observed in suberan, which contribute to a glyceryl structural entity. The long-chain polymethylenic structures demonstrate a high degree of crystallinity, providing a primary structural difference between suberan and suberin.

Infra red spectroscopy, flash pyrolysis, thermally assisted hydrolysis and methylation (THM) in the presence of tetramethylammonium hydroxide (TMAH) of cultured and sediment-derived Lingulodinium polyedrum (Dinoflagellata) cyst walls

The macromolecular composition of dinoflagellate cyst walls is poorly understood and is usually referred to as ‘sporopollenin-like’. We have carried out micro-Fourier transform infra red (micro-FTIR) analysis of chemically untreated sediment-derived and enzymatically and chemically purified culture-derived Lingulodinium polyedrum cyst walls, which suggests an aliphatic polymer rich in C O bonds and relatively poor in CH 2 and CH 3 groups, and which is much closer to cellulose than to sporopollenin or algaenan. This is in agreement with flash pyrolysis–gas chromatography–mass spectrometry (py–GC–MS), with and without tetramethylammonium hydroxide (TMAH) of purified culture derived cyst walls, which indicated an oxygen-rich polymer without normal or isoprenoid carbon chains. The results support a strongly cross-linked carbohydrate-based polymer and as such confirm earlier hypotheses that the cysts were unlike algaenan or sporopollenin, contrasting with the suggestion that the cyst walls were highly aromatic and contained tocopherol as a major monomeric building block.

Investigation of the pyrolysis mechanisms of cellobiose in the presence of a polysiloxane

Treatment of cellulose yarns by a polysiloxane followed by a fast pyrolysis step gave carbon fibres exhibiting strong enhancement of their mechanical resistance. To account for the beneficial effect of the polysiloxane, an investigation of the pyrolysis mechanisms was performed on a model system based on cellobiose and a polysiloxane resin. A chemical interaction between cellobiose and the resin (e.g. grafting of siloxane fragments onto the cellobiose) was established by using various physicochemical analysis techniques: nuclear magnetic resonance (NMR), photoelectron spectrometry (XPS), electronic paramagnetic resonance (EPR), Flash pyrolysis–gas chromatography–mass spectrometry (FP/GC/MS) and IR.

Analysis of organic matter by flash pyrolysis-gas chromatography–mass spectrometry in the presence of Na-smectite: When clay minerals lead to identical molecular signature

Different studies have already pointed out the influence of clays during the analysis of pure organic compounds (especially alkanols, alkanoic acids) as well as macromolecules (humic acids) by flash pyrolysis-gas chromatography–mass spectrometry (PyGC–MS). Especially, the occurrence of clay minerals favors the generation of aromatic units such as alkylbenzenes and polycyclic aromatic hydrocarbons. So as to better identify the nature of the organic compounds which are sensitive to the presence of clays during flash pyrolysis, a humic acid mixed in variable proportions of a Na-homoionic clay was tested. The smectite/humic acid mixtures containing from 10% to 100% humic acid allowed us to identify the progressive disappearance or appearance of specific compounds after PyGC–MS. n-Alk-1-enes disappear when the clay proportion is higher than 67%. For higher contents of Na-smectite, n-alkanes become less and less abundant with a preferential consumption of high molecular weight n-alkanes, whereas the aromatic hydrocarbon proportion increases. Moreover, the distribution of each aromatic hydrocarbon family (alkylbenzenes and alkylnaphthalenes) has been investigated. The pyrogram of pure humic acid exhibits a specific distribution of alkylbenzenes and alkylnaphthalenes reflecting the structure of the organic macromolecule. With the increase in clay proportion, these distributions are modified and lead to other distributions with a preferential predominance of thermally stable isomers. Pyrograms of humic acid and undecanoic acid in the presence of 90% of Na-smectite are similar, especially concerning alkylbenzene and alkylnaphthalene distributions. Therefore, clays (Na-smectite in our experiments) in high proportion modify initial organic products by recombination reactions and lead to the generation of new compounds of very similar distribution, whatever the nature of the initial organic matter. Such results underline the very important catalytic properties of clay minerals on functionalized organic matter during flash pyrolysis.

Aromatization of organic matter induced by the presence of clays during flash pyrolysis-gas chromatography–mass spectrometry (PyGC–MS): A major analytical artifact

The macromolecular characterization of fossil or recent organic matter in soils and sediments is frequently carried out using flash pyrolysis-gas chromatography—mass spectrometry (PyGC–MS). Such analyses providing information on the organic matter structure and reactivity, can be applied on isolated organic materials or on raw samples. Nevertheless, working on pure organic material implies heavy and time-consuming pre-treatments (humic substance isolation, mineral removal by acids), which can induce molecular alteration of the initial organic matter. On the contrary, PyGC–MS analysis on raw sample avoids heavy preparation. However, previous studies have shown that mineral matrixes and especially clay can induce analytical artifacts. The aim of this study is to test clay influences during the flash pyrolysis of pure organic compounds, which can be generated during pyrolysis of natural macromolecules and humic acid. Moreover, flash pyrolysis was carried out with and without a methylation derivative so as to evaluate its ability to limit clay effects. Pyrolysis of Na-smectite/model compounds mixtures indicates that clays intensify recombination reactions. For instance, in the presence of Na-smectite, aromatization increases as a function of the organic compound polarity. Especially, alkyl-benzenes and polycyclic aromatic hydrocarbons are generated during pyrolysis of alkanol, alkanal and especially alkanoic acid. The pyrolysis of humic acid in the presence of clays was also carried out and reveals that clays significantly affect initial molecular distribution especially by intense aromatization. Moreover, the aromatization degree is dependant on the nature of the clay, Na-smectite exhibiting the most intense influence on the molecular signature. Whatever the nature of the organic matter (model compounds or humic acid), the thermally assisted hydrolysis and methylation allows to limit clay interactions and seems a promising way of raw sediments and soils investigation.

Molecular structure of kerogens from source rocks of the Tarim Basin: A study by Py-GC-MS and methylation-Py-GC-MS

Flash pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) and in situ methylation-pyrolysis-gas chromatography-mass spectrometry (methylation-Py-GC-MS) have been employed for a study of molecular structure of kerogens from source rocks of the Tarim Basin. The main products from Py-GC-MS of the Ordovician and Triassic kerogens from the Tarim Basin are n-alkanes and n-alk-1-enes which decrease in relative abundance with increased carbon number. The major products from methylation-Py-GC-MS are normal saturated fatty acid methyl esters which show maxima at C16 and C18. These aliphatic compounds are mainly from lipids of planktonic algae. Moreover, there are more abundant long-chain fatty acids (C20-C26) and normal n-alkanes and n-alk-1-enes (C15-C25) in pyrolysates of Triassic kerogens than that of Ordovician kerogens, reflecting the discrepancies in sources of the Triassic kerogens and the Ordovician kerogens. Besides these aliphatic compounds, methoxyl benzoic acid methyl esters were detected only in products from methylation-Py-GC-MS of late Ordovician kerogen TAC1-1, which possibly was the first molecular evidence for the appearance of moss or other terrestrial plants in the Tarim Basin. In addition, the relative intensity of 17β(H)-trisnorhopane, 17 β(H), 21 α(H)-30-normoretane and 17 β(H)-moretane is lower, but 17α(H)-trisnorhopane and 17 α(H)-30-norhopane is higher in the pyrolysates of the Ordovician kerogens in comparison with the pyrolysates of the Triassic kerogens. Moreover, Pr-1-ene has been detected in pyrolysates of Triassic kerogens. These differences in pyrolysates consist with maturity of kerogens. In conclusion, combination of methylation-Py-GC-MS and Py-GC-MS are useful tools to investigate the molecular structure of geomacromolecules and can be subject to type the organic matter, compare the maturity of kerogens and carry out the oil-source correlation.

Flash pyrolysis – a rapid method for screening bacterial species for the presence of bacteriohopanepolyols

Flash pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS) was applied to freeze dried cells of eleven bacterial species. Six species known to synthesise bacteriohopanepolyols (BHPs) were found to produce easily identifiable C 27–C 35 hopenes and hopanes upon flash pyrolysis. These compounds could not be observed in the pyrolysis products of five species, two of which are known not to produce BHPs. In the search for BHP-containing bacteria this rapid screening approach prevents unnecessary time-consuming laboratory work to characterise species that would produce negative results.

Preferential accumulation of selectively preserved biomacromolecules in the humus fractions from a peat deposit as seen by analytical pyrolysis and spectroscopic techniques

A series of structural features of the three main humic fractions (humic acid, fulvic acid and humin) from different depths of a peat bog deposit in Mazagón (Huelva, Southern Spain) were isolated and analysed by flash pyrolysis–gas chromatography–mass spectrometry, solid-state 13C-nuclear magnetic resonance and Fourier transformed infrared spectroscopy. Such techniques demonstrate that the various humic fractions were very different not only in terms of molecular weight but also in their composition and structural characteristics, showing well differentiated patterns in the relative distribution of alkyl, O-alkyl and aromatic moieties in each humic fraction. To a large extent, selectively preserved lignin accumulates in the humic acid (HA) fraction, whereas the fulvic acid (FA) consists of a colloidal carbohydrate with a substantial peptidic moiety and the humin includes the noteworthy concentration of insoluble, macromolecular polyalkyl structures. A diagnostic lignin signature in the resolution-enhanced infrared spectra of the HA points to processes of selective preservation of macromolecular substances derived from vascular plants. In general, the humic fractions were not extensive sources of chemotaxonomic descriptors of previously documented biodiversity changes along the period of the peat deposit formation. This is in harmony with a substantial homogenising effect of diagenetic transformations throughout the whole sedimentary record with peat stratigraphy recording mostly the authigenic processes of bog formation and development. Anthropogenic perturbations may be also responsible for the loss of information in the humic proxy resulting in the lack of an apparent relationship between any particular input and the composition of the humic fractions from the peat bog.

High molecular weight organic matter in martian meteorites

We have performed an investigation to detect high molecular weight organic matter in martian meteorites. Solvent-extracted samples of two Antarctic finds (ALH 84001, sub-sample 106 and EET A79001, sub-sample 351) and one non-Antarctic fall (Nakhla) were analysed by flash pyrolysis–gas chromatography–mass spectrometry. Results suggest that our sub-sample of ALH 84001 contains no pyrolysable organic matter. In contrast, our samples of EET A79001 and Nakhla contain organic matter of high molecular weight, which releases aromatic and alkylaromatic hydrocarbons, phenol and benzonitrile as major compounds upon pyrolysis. The detection of similar pyrolysis products from Nakhla and EET A79001 indicates that these martian meteorites may have a common high molecular weight organic phase. Carbon isotopic measurements of individual molecules in the Nakhla pyrolysate, by flash pyrolysis–gas chromatography–isotope ratio mass spectrometry, reveal that this high molecular weight organic matter has some similarities to that found in carbonaceous chondrites. At this point, an origin by terrestrial contamination cannot be unequivocally ruled out, but the data seem to support proposals that martian samples contain organic matter originating from meteoritic infall on Mars. The results suggest that a wider, pyrolysis-based study of martian meteorites would be a justifiable use of these precious samples.

A Py–GC–MS and NMR spectroscopy study of organic nitrogen in Mangrove Lake sediments

Solid-state CP–MAS 13C and 15N nuclear magnetic resonance (NMR) spectroscopy and flash pyrolysis–gas chromatography–mass spectrometry (Py-GC–MS) techniques have been used to characterize the organic-rich sedimentary deposit from Mangrove Lake, Bermuda. The chemical nature of organic nitrogen in sediment samples from different depths was studied as it relates to the early diagenesis of proteinaceous material in the reducing marine environment. Although the majority of proteins were lost during early diagenesis, part of the proteinaceous material became resistant to proteolysis and chemical hydrolysis. The proteinaceous material is proposed to have survived early diagenesis via encapsulation by refractory, aliphatic organic matter.

Rapid contamination screening of river sediments by flash pyrolysis-gas chromatography–mass spectrometry (PyGC–MS) and thermodesorption GC–MS (TdGC–MS)

For 20 years, pyrolysis-gas chromatography–mass spectrometry (PyGC–MS) has been currently used in order to improve the knowledge on recent (soils and sediments) and fossil complex organic matter. Actually, PyGC–MS is also proposed as a rapid tool for the investigation of different types of sediment contaminations. Such rapid investigations allowed to increase the number and the frequency of the controls of river sediments, which are generally time and money consuming. However, during flash pyrolysis, the molecules generated derive from both macromolecules breakdown and thermovaporization of free compounds. Then, a methodology allowing the fractionation of these two types of effluents should be developed. Two river sediments showing different contamination degrees have been investigated in order to test the different modes of pyrolysis. The efficiency of thermodesorption-gas chromatography–mass spectrometry (TdGC–MS) at low temperature (300°C) for the study of free molecules (PAH, hydrocarbons, …) is compared with the results derived from traditional analysis (extraction, liquid chromatography and GC–MS). On the other hand, pyrolysis of pre-thermodesorbed sediments is carried out in order to analyze the residual organic matter. However, the use of thermodesorption instead of solvent extraction for free organic matter removal is not always efficient especially for high molecular mass compounds. On the other hand, although heavy molecular mass compounds are frequently underestimated, the use of TdGC–MS remains an efficient tool for the rapid screening for contaminant investigation. Moreover, low molecular mass organic compounds which are generally lost during traditional pre-treatment (extraction followed by reconcentration steps) are detected after thermodesorption of the raw sediment.

Analysis of pitch deposits produced in Kraft pulp mills using a totally chlorine free bleaching sequence

Two organic deposits accumulated in a Kraft pulp mill during pulping of Eucalyptus globulus wood and throughout a TCF (totally chlorine free) bleaching sequence were characterized. One deposit was collected after cooking and an oxygen delignification stage while the other was collected after bleaching with hydrogen peroxide. The deposits were Soxhlet extracted with acetone, and the extracts redissolved in chloroform and subsequently analyzed by gas chromatography (GC) and GC–mass spectrometry (MS) using short and medium length high temperature capillary columns, respectively. On the other hand, the insoluble residues left after the acetone extraction were analyzed by Curie-point flash pyrolysis–GC–MS and by pyrolysis–methylation–GC–MS. The compounds identified in the deposits arise from the E. globulus wood lipophilic extractives that survive the pulping and bleaching processes. Triglycerides were completely hydrolyzed during the Kraft cooking and the fatty acids dissolved. Steroids (alcohols, hydrocarbons, ketones and esters) and waxes were the main components in the deposit collected after the oxygen delignification stage. After the bleaching with hydrogen peroxide, content of the waxes were reduced and fatty acids appeared. High amounts of fatty acids salts were also identified in the deposit collected after the oxygen stage, and in minor amounts in the deposit collected after hydrogen peroxide bleaching. In contrast, this deposit was mainly made up of high amounts of lignin-derived phenolic moieties.

99/00996 Solid state 13C NMR and high temperature 1H NMR determination of bulk structural properties for mesophase-containing semi-cokes prepared from coal tar pitch : Andresen, J. M. et al. Carbon, 1998, 36, (7–8), 1043–1050

The coalified remains of three extinct nonvascular Lower Devonian plants (Prototaxites Dawson, Pachytheca Hooker, and Parka Fleming) have been analysed using flash pyrolysis-gas chromatography-mass spectrometry, FTIR, and 13C solid-state NMR. The affinities of these fossils are unknown and their habitats remain conjectural. Host rock lithology and grain size correlate with the state of morphological and chemical preservation of Prototaxites. The flash pyrolysates of well-preserved Prototaxites and Pachytheca were dominated by aromatic hydrocarbons and alkylphenols. Given their resistance to compression when compared with associated lignified vascular plant fossils, it is possible that Prototaxites and Pachytheca contained an extinct polyphenolic structural biomacromolecule that was a failed experiment during terrestrialization. Precise affinities for the enigmatic fossils Prototaxites, Pachytheca, and Parka are still to be confirmed, although Prototaxites and Pachytheca are chemically distinct from Parka.

Molecular characterization of some enigmatic Lower Devonian fossils

The coalified remains of three extinct nonvascular Lower Devonian plants ( Prototaxites Dawson, Pachytheca Hooker, and Parka Fleming) have been analysed using flash pyrolysis-gas chromatography-mass spectrometry, FTIR, and 13C solid-state NMR. The affinities of these fossils are unknown and their habitats remain conjectural. Host rock lithology and grain size correlate with the state of morphological and chemical preservation of Prototaxites. The flash pyrolysates of well-preserved Prototaxites and Pachytheca were dominated by aromatic hydrocarbons and alkylphenols. Given their resistance to compression when compared with associated lignified vascular plant fossils, it is possible that Prototaxites and Pachytheca contained an extinct polyphenolic structural biomacromolecule that was a failed experiment during terrestrialization. Precise affinities for the enigmatic fossils Prototaxites, Pachytheca, and Parka are still to be confirmed, although Prototaxites and Pachytheca are chemically distinct from Parka.

98/01060 Determination of gasoline properties using 1H-NMR spectroscopy : Hutter, M. et al. Pet. Coal, 1995, 37, (3), 50–52

The coalified remains of three extinct nonvascular Lower Devonian plants (Prototaxites Dawson, Pachytheca Hooker, and Parka Fleming) have been analysed using flash pyrolysis-gas chromatography-mass spectrometry, FTIR, and 13C solid-state NMR. The affinities of these fossils are unknown and their habitats remain conjectural. Host rock lithology and grain size correlate with the state of morphological and chemical preservation of Prototaxites. The flash pyrolysates of well-preserved Prototaxites and Pachytheca were dominated by aromatic hydrocarbons and alkylphenols. Given their resistance to compression when compared with associated lignified vascular plant fossils, it is possible that Prototaxites and Pachytheca contained an extinct polyphenolic structural biomacromolecule that was a failed experiment during terrestrialization. Precise affinities for the enigmatic fossils Prototaxites, Pachytheca, and Parka are still to be confirmed, although Prototaxites and Pachytheca are chemically distinct from Parka.

Flash pyrolysis of the outer cortical tissues in Lower DevonianPsilophyton dawsonii

Coalified residues of the xylem and peripheral structure tissues (stereome) from permineralized (CaCO3) Lower DevonianPsilophyton dawsoniihave been analysed by flash pyrolysis-gas chromatography-mass spectrometry. Both yielded C0-C1alkylphenols, C1-C3alkylbenzenes, C0-C1alkylnaphthalenes, although with varying relative abundances. The stereome also generated a series ofn-alk-1-enes andn-alkanes (C8-C24, maximum at C10) which is believed to be derived from the cuticle. The sources of the aromatic compounds are discussed, and while it is concluded that those in the xylem are derived from lignin, the macromolecule having been degraded by diagenesis and thermal maturation, the molecular sources of those from the stereome may also include a wide range of substances including simple phenolic acids, flavonoids and non-lignin polyphenolics. Possible functions for the stereome are discussed.

Flash pyrolysis of the outer cortical tissues in Lower Devonian Psilophyton dawsonii

Coalified residues of the xylem and peripheral structure tissues (stereome) from permineralized (CaCO3) Lower Devonian Psilophyton dawsomi have been analysed by flash pyrolysis-gas chromatography-mass spectrometry. Both yielded C1-3 alkylphenols, C1-3 alkylbenzenes, C1-3 alkylnaphthalenes, although with varying relative abundances. The stereome also generated a series of n-alk-1-enes and n-alkanes (C3C24, maximum at C10) which is believed to be derived from the cuticle. The sources of the aromatic compounds are discussed, and while it is concluded that those in the xylem are derived from lignin, the macromolecule having been degraded by diagenesis and thermal maturation, the molecular sources of those from the stereome may also include a wide range of substances including simple phenolic acids, flavonoids and non-lignin polyphenolics. Possible functions for the stereome are discussed.