Curie-point Pyrolysis-gas Chromatography-mass Spectrometry Research Articles

Assessing anthropogenic contribution to PM2.5 from an urban residential area of Lagos, Nigeria using aliphatic hydrocarbon compounds as indicators

Aliphatic hydrocarbons in PM2.5 samples from a residential area of Lagos, Nigeria, were quantified using a Curie-point pyrolysis–gas chromatography–mass spectroscopy (CPPGC/MS). The total concentrations of ∑n-alkanes (C20-C34), hopanes (∑4Hopanes), and steranes (∑3Steranes) ranged from 1.8 to 146.6 ng m-3 (avg. 43.6 ± 35.1 ng m-3), 0.0 to 89.9 ng m-3 (avg. 18.7 ± 25.9 ng m-3), and 0.0 to 26.0 ng m-3 (avg. 3.3 ± 6.7 ng m-3), accounting for 0.2%, 0.1%, and 0.01% of the total PM2.5 mass concentrations, respectively. They also accounted for, 1%, 0.4% and 0.1% of the organic matter content, respectively, making them non-negligible component of the organic matter in this region. An evaluation of the n-alkanes source diagnostic indices revealed that engines powered by gasoline and diesel were the main sources of particulate matter aliphatic hydrocarbons in this area of Lagos, consistent with the results obtained from steranes and hopanes profiles. Based on the air mass trajectories, both local and regional air mass transports showed a significant influence on the amounts of carbonaceous materials and aliphatic hydrocarbon compounds arriving at the study site. The results from this study established the occurrence of anthropogenic air pollution in Lagos residential area with a major contribution from petrogenic sources.

Chemical and structural changes in vitrinites and megaspores from Carboniferous coals during maturation

Chemical and structural changes occurring in kerogen upon thermal alteration are identified and analysed based on a set of naturally matured Carboniferous coals from the Ruhr Basin (Germany). For this purpose, handpicked vitrinite from eleven samples comprising a maturity range from 0.55 to 2.86% VRr was analysed using attenuated total reflectance infrared spectroscopy (ATR FT-IR) and Curie Point pyrolysis gas chromatography/mass spectroscopy (CP-Py-GC/MS) at two pyrolysis temperatures. Additionally, reflectance μFT-IR was used to assess variations in the proportions of functional groups in megaspores from five oil mature coal samples. Infrared spectra of the vitrinites show a clear decrease in aliphatic CHx absorbance in favour of aromatic CH absorbance, pointing out an increase in aromaticity with increasing maturity. Spectra of megaspores are dominated by the absorbance of the aliphatic CHx stretching region and reveal the loss of C=O groups with increasing maturity, while the degree of aromaticity (γCH/νCHx) increases slowly compared to that of the vitrinite spectra. Vitrinites pyrolysed at 590°C show higher yields in aliphatic hydrocarbons than those pyrolysed at 764°C, while at the higher pyrolysis temperature the yields in aromatic compounds, including phenols and sulphur-containing aromatics are higher. The aromatic fraction of the pyrolysates, in particular the relative amount of polyaromatics increases upon maturation, while the phenolic fraction decreases in favour of benzenes. Major processes leading to these structural and chemical changes in vitrinites and megaspores are defunctionalisation of oxygen-containing groups, the loss of aliphatic compounds and the formation of monoaromatic molecules. These prevail over the condensation of aromatic ring-structures, which is, however, evidenced by increasing proportions of polyaromatic fractions in the pyrolysed vitrinites.

Simultaneous Trace Identification and Quantification of Common Types of Microplastics in Environmental Samples by Pyrolysis-Gas Chromatography-Mass Spectrometry.

The content of microplastics (MP) in the environment is constantly growing. Since the environmental relevance, particularly bioavailability, rises with decreasing particle size, the knowledge of the MP proportion in habitats and organisms is of gaining importance. The reliable recognition of MP particles is limited and underlies substantial uncertainties. Therefore spectroscopic methods are necessary to ensure the plastic nature of isolated particles, determine the polymer type and obtain particle count related quantitative data. In this study Curie-Point pyrolysis-gas chromatography-mass spectrometry combined with thermochemolysis is shown to be an excellent analytical tool to simultaneously identify and optionally quantify MP in environmental samples on a polymer specific mass related trace level. The method is independent of any mechanical preselection or particle appearance. For this purpose polymer characteristic pyrolysis products and their indicative fragment ions were used to analyze eight common types of plastics. Further aspects of calibration, recoveries, and potential matrix effects are discussed. The method is exemplarily applied on selected fish samples after an enzymatic-chemically pretreatment. This new approach with mass-related results is complementary to established FT-IR and Raman methods providing particle counts of individual polymer particles.

Chemotaxonomy of fossil woods from the Lower Rhine Embayment, Germany

In the Lower Rhine Embayment (western Germany), the Neogene lignite bearing sequence is rich in large fossil wood trunks. Woods collected from sand-filled channels of a meandering river system (Pliocene: Reuver series) and from coal seams (Miocene: seams Garzweiler, Frimmersdorf and Morken) were investigated by Curie-point pyrolysis coupled with gas chromatography–mass spectrometry in order to determine their palaeobotanical classification. In comparison with reference data of individual pyrograms of modern woods, it became possible to classify 15 fossil wood trunks chemotaxonomically as follows: eleven samples were identified as Taxodioxylon sp. by reference Sequoia sempervirens, three samples were identified as Populoxylon sp. by reference Populus nigra and one sample was identified as Sciadopityoxylon sp. by two references of Sciadopitys verticillata. Microanatomical crosschecks describe the equivalent samples taxonomically as Taxodioxylon gypsaceum (GÖPPERT) KRÄUSEL, Taxodioxylon germanicum (GREGUSS) VAN DER BURGH, Populus nigra L. and Sciadopityoxylon wettsteinii JURASKY, and confirm the chemical classifications. For both fossil and reference woods, our relative quantifications of guaicyl and syringyl moieties are in precise accordance with discriminations of gymnosperms versus angiosperms. This means that not only unknown recent woods can chemotaxonomically accurately be determined by Curie-point pyrolysis gas chromatography–mass spectrometry and their equivalent modern wood reference from our data base, but also the taxonomy of botanically related wood types reaching back to the geological past up to a Miocene age at least.

Effectiveness of combination lisinopril+hydrochlorothiazide vs. bisoprolol+hydrochlorothiazide in patients with moderate to severe hypertension

Previous work suggests that polycarboxylic acids can be regarded as model compounds for soil fulvic acids and for water-soluble soil organic polymers. Curie-point pyrolysis—gas chromatography—mass spectrometry studies indicate that, on pyrolysis, polycarboxylic acids undergo fragmentation with cyclisation, elimination and decarboxylation reactions and yields two characteristic produces, 2-cyclopenten-1-one and 2,3-dimethylmaleic anhydride. The former is a characteristic pyrolysis product of solids and has been used in the assessment of humus type. Aromatic and phenolic products are also obtained in smaller amounts depending on the polymer molecular weight. Fulvic acids and water-extracted soil organic matter give similar pyrolysis products, together with those derived from polysaccharides and polypeptides. These results support the concept that natural soil organic polymers contain significant amounts of highly carboxylated chains.

An 18th century medication “Mumia vera aegyptica” – Fake or authentic?

The drug “mumia vera” has a long tradition in ancient medicine. It was considered an omnipotent panacea for a broad spectrum of diseases based on virtue associated with asphalt and other bituminous substances combined with the belief in the magic healing power of death. This made it a precious ingredient of medication and it represents a particular facet of medicinal cannibalism. “Mumia” was a common, and much sought after, component of pharmacists’ stock in trade, particularly in the Middle Ages. A shortage of sources for authentic mummies from Egypt resulted in the production of fakes, including dried human bodies. A rare tiny residue in a historic 18th century pharmaceutical vessel labelled MUMIA was microscopically subsampled and analysed with Curie point pyrolysis–gas chromatography–mass spectrometry (CP-py-GC–MS) and GC–MS. From the data (e.g. fatty acids, terpenes, triterpenoids, n-alkanes, n-alkenes, wax esters) there is strong evidence that the vessel contained authentic mummy material. All subsamples could be put into a logical context of the mummification process and its product, i.e. fibres from bandages, wrappings or filling material, conifer wood fibres as a possible part of cover material, “used” embalming material in the form of a mixture of cedrium, pistachia resin (possibly Chios turpentine) and beeswax, (hydrolysed) fat (evidently including human sebum, possibly adipocere), mummified skin or tissue (possibly treated with polyunsaturated plant oil, highly oxidised by the time of analysis) and Dead Sea asphalt with a possible admixture of some asphalt from a different source.

Influence of different fermentation raw materials on pyrolyzates of Pu-erh tea theabrownin by Curie-point pyrolysis-gas chromatography–mass spectroscopy

ScopeIn this study, Pu-erh tea was prepared by solid-state fermentation of the sun-dried green tea, short-fermentation black tea, and black tea. Ultraviolet-visible spectroscopy, infrared spectroscopy and Curie-point pyrolysis-gas chromatography–mass spectroscopy (CP-Py-GC/MS) were used to study the characteristics and chemical compositions of the TB formed in these Pu-erh teas. Methods and resultsThe pyrolysates of the Pu-erh teas’ theabrownin (TB1, TB2, TB3) were analyzed at 386°C using a Curie point pyrolysis instrument. TB1, TB2, and TB3 produced 158, 135 and 148 pyrolysis products, respectively. These compounds could be grouped as follows: alkaloids, 25.23% (TB1), 25.67% (TB2), and 21.91% (TB3); phenols, 24.19% (TB1), 23.08% (TB2), and 29.91% (TB3); nitrogen-compounds, 11.79% (TB1), 11.25% (TB2), and 13.39% (TB3); hydrocarbons, 10.96% (TB1), 10.37% (TB2), and 11.37% (TB3); ketones, 10.34% (TB1), 6.58% (TB2), and 8.22% (TB3); furan, 5.40% (TB1), 4.06% (TB2), and 2.33% (TB3); alcohol, 3.30% (TB1), 4.16% (TB2), and 3.34% (TB3); fatty acids, 2.80% (TB1), 4.03% (TB2), and 1.42% (TB3); esters 2.17% (TB1), 0.99% (TB2) and 2.35% (TB3); and amines 1.61% (TB1), 2.81% (TB2), and 0.86% (TB3). ConclusionTheabrownin mainly contains alkaloids (caffeine), tea pigments, polysaccharides, proteins and lipids. Its precursors include various polyphenols, tea pigments, alkaloids, polysaccharides, proteins and lipids. These compounds in the raw materials impact the chemical composition of theabrownin, and black tea is not a suitable raw fermentation material for Pu-erh tea.

Curie-point pyrolysis–gas chromatography–mass spectroscopic analysis of theabrownins from fermented Zijuan tea

Zijuan tea theabrownins (ZTTBs) was extracted from a type of fermented Zijuan tea and separated into fractions according to molecular weight. The extract was found to contain predominantly two fractions: <3.5kDa and >100kDa. These two fractions were analyzed for chemical composition, structural characteristics by Curie-point pyrolysis–gas chromatography–mass spectroscopy (CP-Py–GC/MS). The affects of pyrolysis temperature on pyrolytic products were also investigated. The fraction >100kDa produced 50 GC/MS peaks during pyrolysis at 280°C, 70 peaks at 386°C, and 134 peaks at 485°C. Fourteen of the products formed at 280°C, 12 of those formed at 386°C, and 21 of those formed at 485°C were identified with match qualities of greater than 80%. The fraction <3.5kDa gave 51 peaks during pyrolysis at 280°C, 99 peaks at 386°C, and 257 peaks at 485°C. Six products formed at 280°C, four products formed at 386°C, and 61 products formed at 485°C were identified with match qualities of greater than 80%. Pyrolysis temperatures of 485°C and 386°C were found suitable for the two fractions respectively. CP-Py–GC/MS revealed that, the fraction >100kDa mainly consisted of phenolic pigments, esters, proteins, and polysaccharides, while the fraction <3.5kDa contained no polysaccharide. CP-Py–GC/MS is an effective tool for the composition difference and structural characteristics of ZTTBs as well as other complex macromolecular plant pigments.

Characterization of the chemical differences between solvent extracts from Pu-erh tea and Dian Hong black tea by CP–Py–GC/MS

Solvent extracts from a type of Pu-erh tea and Dian Hong black tea were characterized by Curie-point pyrolysis–gas chromatography–mass spectroscopy (CP–Py–GC/MS). The ethyl-acetate extracts from both teas showed similar CP–Py–GC/MS results, with main pyrolytic products of carbon dioxide, caffeine, o-phenols, and phthalate esters. During pyrolysis, the n-butanol extract from Pu-erh tea formed carbon dioxide (38.92% of total pyrolytic products), alkaloids (49.7%), and nitrogen oxides (8.38%), as well as a small fraction of esters. The n-butanol extract from Dian Hong tea formed mainly alcohols, amines, esters, phenols, carboxylic acids, and alkaloids. The raw theabrownin extracts (ethanol precipitates) from the two teas produced substantially different CP–Py–GC/MS results. The raw theabrownin extract from Pu-erh tea formed mostly carbon dioxide during pyrolysis, whereas the counterpart extract from Dian Hong tea formed mainly carbon dioxide (48.23%) and nitrogen oxides (35.39%). The 3.5–100kDa fractions separated from the theabrownin extracts of the two teas showed similar CP–Py–GC/MS results, whereas the fractions <3.5kDa and >100kDa formed substantially different pyrolytic products. These results showed that solvent extracts from Pu-erh tea and Dian Hong tea had substantially different chemical compositions and structures. The study suggested that CP–Py–GC/MS can be used to effectively identify chemical differences between tea extracts.

Relative contribution of foliar and fine root pine litter to the molecular composition of soil organic matter after in situ degradation

The influence of litter quality on soil organic matter (SOM) stabilization rate and pathways remains unclear. We used 13C/ 15N labeled litter addition and Curie-point pyrolysis gas chromatography–mass spectrometry combustion-isotope ratio mass spectrometry (Py–GC–MS–C–IRMS) to explore the transformation of litter with different composition and decay rate (ponderosa pine needle vs. fine root) to SOM during 18 months in a temperate conifer forest mineral (A horizon) soil. Based on 13C Py–GC–MS–C–IRMS the initial litter and bulk soil had ∼1/3 of the total pyrolysis products identified in common. The majority was related either to carbohydrates or was non-specific in origin. In bulk soil, carbohydrates had similar levels of enrichment after needle input and fine root input, while the non-specific products were more enriched after needle input. In the humin SOM fraction (260 yr C turnover time) we found only carbohydrate and alkyl C-derived compounds and greater 13C enrichment in the “carbohydrate” pool after fine root decomposition. 15N Py–GC–MS–C–IRMS of humic substances showed that root litter contributed more than needle litter to the enrichment of specific protein markers during initial decomposition. We found little evidence for the selective preservation of plant compounds considered to be recalcitrant. Our findings suggest an indirect role for decomposing plant material composition, where microbial alteration of fine root litter seems to favor greater initial stabilization of microbially derived C and N in SOM fractions with long mean turnover times, such as humin, compared to needles with a faster decay rate.

Ionic liquids as media for biomass processing: opportunities and restrictions

Abstract The present study provides insight into the dissolution behavior of renewable materials in ionic liquids. Beech, spruce and rye straw were dissolved in 1-ethyl-3-methylimidazolium acetate as the ionic liquid of choice, which is currently one of the most frequently used cation-anion combinations among ionic liquids for biomaterial processing. The dissolution was followed by selective precipitation of cellulose, hemicelluloses, and lignin. The obtained lignin was analyzed with Curie-point pyrolysis gas chromatography/mass spectrometry (Cu-Py-GC/MS) and the separated cellulose/hemicellulose fractions with gel permeation chromatography (GPC). Time dependence of the dissolution process was studied on rye straw, eucalyptus kraft pulp and beech sulfite pulp. The results show a changing dissolution profile over time, which is due to progressing degradation of the cellulose in the ionic liquid.

Chemical composition and palaeobotanical origin of Miocene resins from Kerala-Konkan Coast, western India

The terpenoid composition of resins from the Miocene lignite horizons from the Kerala-Konkan Coast, western India was analyzed by Curie-point pyrolysis-gas chromatography-mass spectrometry (Cupy-GC-MS). The major pyrolysates were cadalene-based bicyclic sesquiterpenoids including some C30-C31 bicadinenes and bicadinanes typical of dammar resin from angiosperm plants of Dipterocarpaceae family. These plants are typically supported by tropical climates which the western Indian region was known to have experienced during early Tertiary period. The present study suggests that these palaeoclimatic conditions persisted until at least the Miocene epoch. These sesquiterpenoids which are commonly detected in many SE Asian crude oils may be utilised as useful biomarkers for petroleum exploration in the western Indian region.

Terpenoid composition and botanical affinity of Cretaceous resins from India and Myanmar

Fossil resins from the Cretaceous sediments of Meghalaya, India and Kachin, Myanmar (Burma) were analysed using Curie point pyrolysis–gas chromatography–mass spectrometry and thermochemolysis gas chromatography–mass spectrometry to help elucidate their botanical source. The major pyrolysis products and methyl-esterified thermochemolysis products of both the resins were abietane and labdane type diterpenoids with minor amount of sesquiterpenoids. The thermochemolysis products also included methyl-16,17-dinor callitrisate, methyl-16,17-dinor dehydroabietate and methyl-8-pimaren-18-oate—the latter two from just the Myanmarese resin. The exclusive presence of both labdane and abietane diterpenoids and the lack of phenolic terpenoids may suggest that the studied Cretaceous resins were derived from Pinaceae (pine family) conifers. ► The chemical composition of Cretaceous resins from India and Myanmar was investigated. ► Abietane and labdane type diterpenoids are the major pyrolysis products. ► These resins were probably derived from Pinaceae conifers.

Macromolecular composition of Palaeozoic scolecodonts: insights into the molecular taphonomy of zoomorphs

Dutta, S., Hartkopf-Fröder, C., Mann, U., Wilkes, H., Brocke, R. & Bertram, N. 2010: Macromolecular composition of Palaeozoic scolecodonts: insights into the molecular taphonomy of zoomorphs. Lethaia, Vol. 43, pp. 334–343. Biogeochemistry and molecular taphonomy of biopolymers of marine zoomorphs are poorly known. In order to obtain insights into this issue we report on the biogeomacromolecular composition of hand-picked, well-preserved scolecodonts of Ordovician, Silurian and Devonian age using micro-Fourier transform infrared (micro-FTIR) spectroscopy, Curie point pyrolysis-gas chromatography-mass spectrometry (Cupy-GC-MS) and tetramethylammonium hydroxide (TMAH)-assisted thermochemolysis-GC-MS. The present study reveals that scolecodonts are composed of both aliphatic and aromatic moieties. The micro-FTIR spectra of scolecodonts are characterized by aliphatic CHx (3000–2800 and 1460–1450/cm) and CH3 (1375/cm) absorptions and aromatic C=C (1560–1610/cm) and CH (3050/cm and 700–900/cm) absorptions. The major pyrolysis products from the scolecodonts include aromatic hydrocarbons such as alkylbenzenes, alkylnaphthalenes and alkylphenols. Aliphatic hydrocarbons are represented by a homologous series of n-alkenes and n-alkanes. The compounds released upon thermochemolysis with TMAH are saturated and unsaturated fatty acids (as their methyl esters), n-alkenes/alkanes and aromatic acids (as their methyl esters). No protein/amino acid-derived compounds have been recognized in the pyrolysates or in the thermochemolysates, and it is concluded that protein/amino acid-related compounds, which are commonly found in the jaws of extant polychaetes, were destroyed due to diagenetic processes. Obviously, excellent morphological preservation and low thermal alteration are not paralleled by a similar degree of chemical preservation. □Biogeomacromolecules, micro-FTIR, pyrolysis-GC-MS, scolecodonts, thermochemolysis-GC-MS.

Highly aromatic character of biogeomacromolecules in Chitinozoa: A spectroscopic and pyrolytic study

Extraordinarily well-preserved chitinozoans from an Upper Silurian sedimentary sequence in south-east Turkey were recovered from different depth levels, hand-picked from the palynological residue, cleaned and analysed by micro-FTIR and Curie point pyrolysis-gas chromatography–mass spectrometry. Hand-picked chitinozoans were predominantly represented by the genera Bursachitina, Calpichitina, Cingulochitina, Ancyrochitina, Angochitina and Pterochitina. Both spectroscopic and pyrolytic investigations suggest that biogeomacromolecules of these Chitinozoa consist of both aliphatic and aromatic moieties. The micro-FTIR spectra of Chitinozoa are characterized by aliphatic CH x (3000–2800 and 1460–1450 cm −1) and CH 3 (1375 cm −1) absorptions and aromatic C C (1560–1610 cm −1) and CH (3050 cm −1 and 700–900 cm −1) absorptions. Major pyrolysis products from the Chitinozoa include both aromatic compounds such as alkylbenzenes, alkylnaphthalenes, alkylphenols and alkylphenanthrenes and aliphatic hydrocarbons including a homologous series of n-alkene/ n-alkane doublets. Aromatic compounds predominate over aliphatic compounds. 1,2,3,4-Tetramethylbenzene is the most abundant pyrolysis product of the studied Chitinozoa. No pyrolysis products diagnostic of chitin were detected in the present study and it is unlikely that the original biomacromolecules of Chitinozoa prior to fossilization were made of chitin.

Long-term cultivation effects on the quantity and quality of organic matter in selected Canadian prairie soils

Sixteen Orthic Chernozemic surface soil samples, one half from virgin prairie and one half from adjacent cultivated prairie (cultivated for 31 to 94 years), were collected from eight sites throughout Southern Saskatchewan, Canada. Samples were analyzed for total organic C and a number of other chemical and physical properties. The virgin and cultivated soils at site No. 4 were selected for more detailed analysis by CP-MAS 13C NMR, Curie-point-pyrolysis-gas chromatography/mass spectrometry (Cp-Py-GC/MS), and by pyrolysis-field ionization mass spectrometry (Py-FIMS). Long-term cultivation resulted in large significant decreases in total SOM (soil organic matter), as represented by total soil organic C. There were significant increases in aromaticity of the SOM as a result of long-term cultivation as indicated by CP-MAS 13C NMR spectroscopy. This was mainly attributable to the result of cultivation-enhanced degradation of aliphatic C relative to aromatic C. Organic compounds identified in the Cp-Py-GC/MS spectra of the virgin and cultivated soils at site No. 4 consisted of n-alkanes (ranging from C 11 to C 22) and alkenes (ranging from C 7:1 to C 21:1), with the virgin soil being richer in alkenes than the cultivated soil. Other components identified were cyclic aromatics, carbocyclics, N-containing aromatics, N-heterocyclics, benzene and substituted benzenes, phenols and substituted phenols and substituted furans. The compounds identified appeared to originate from long-chain aliphatics, lignins, polyphenols, aromatics, polysaccharides, and N-containing compounds in the two soils. While qualitatively similar compounds were identified by Py-FIMS in the two soils, the total ion intensity (TII) of the virgin soil was almost 2.5 times as high as that of the cultivated soil. This suggests that cultivation made the organic matter less volatile, either by favouring the formation of higher molecular weight organic matter or by promoting the formation of non-volatile metal-organic matter complexes. The Py-FIMS spectra showed that the virgin soil contained relatively more lignin dimers, lipids, sterols, and n-C 16 to n-C 34 fatty acids than the cultivated soil. Thus, conversely, the cultivated soil was richer in carbohydrates, phenols and lignin monomers, alkyl aromatics and N-containing compounds, including peptides, than the virgin soil.

Comparative study of ligno-cellulosic material from wheat straw and of pure and mixed standard compounds via solid state 13C NMR spectroscopy, conventional pyrolysis and TMAH thermochemolysis

The ligno-cellulosic material (LCS) isolated from wheat straw, via successive acid and base treatments, exhibits high complexing capacities, mostly related to the lignin fraction, and may have important applications for metal completion. In the present study LCS was examined via a combination of spectroscopic and pyrolytic methods: solid slate cross polarization/magic angle spinning 13C nuclear magnetic resonance (CP/MAS 13C NMR), conventional Curie point pyrolysis–gas chromatography–mass spectrometry (CuPy–GC–MS) and tetramethylammonium hydroxide (TMAH) thermochemolysis–GC–MS). Parallel experiments were also performed on cellulose and tignin standards and 50:50 cellulose:lignin mixture. These studies afforded information on lignin:cellulose relative abundances in LCS (ca. 15:85) and on the composition of the lignin fraction, including the presence of substantial amounts of carboxylic groups which should be important for metal complexation. Examination of standards and mixture also illustrated (i) the usefulness of TMAH thermochemolysis for the detection of cellulose and of carboxylic groups compared with conventional pyrolysis and (ii) the conspicuous limitations of some of the above methods when applied to ligno-cellulosic materials and resulting biases.

Pyrolysis-GC-MS analysis of the formation and degradation stages of charred residues from lignocellulosic biomass.

The structural transformations undergone by lignocellulosic biomass (freeze-dried rye grass, Lolium rigidum) subjected to progressive isothermal heating (burning at 350 degrees C under oxidizing conditions for 30, 45, 60, 75, and 90 s) have been monitored by Curie-point pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS). The pyrograms suggest that even charred residues after severe heating (carbon loss ca. 50%) still contain substantial concentrations of some resistant plant structural components. Several trends were observed when monitoring the relative concentrations of the different groups of pyrolysis compounds released during successive charring stages: (i) the tetrapyrrole moiety of chlorophylls is rapidly destroyed as indicated by the decreasing yields of pyrroles and pyrrolines, whereas the phytol backbone is comparatively more resistant, leading to phytadienes after dehydration and reduction; (ii) the increasing yields of imidazoles from progressively heated samples (maximum at 45 s stage) suggest accumulation of newly formed nitrogen-containing compounds that may survive natural fires; (iii) the lignin backbone shows a relative resistance, the yields of aromatic products pointing to progressive demethoxylation; and, (iv) a selective accumulation of recalcitrant alkyl material occurred, which is interpreted as the result of thermal condensation of hydrocarbons and fatty acids into macromolecular materials in the charred residue. In terms of the intensity of the isothermal heating, the yields of the different classes of alkyl compounds follow the order phytadienes < fatty acids < alkanes < wax esters < sterols.

Origin and formation pathways of kerogen-like organic matter in recent sediments off the Danube delta (northwestern Black Sea)

The chemical structure, source(s), and formation pathway(s) of kerogen-like organic matter (KL) were investigated in recent sediments from the northwestern Black Sea, off the Danube delta. Three sections from a sediment core collected at the mouth of the Sulina branch of the delta, under an oxic water column, were examined: S0 (0–0.5 cm bsf), S10 (10–13 cm bsf), and S20 (20–25 cm bsf). The bulk geochemical features of these sediments (total organic carbon, organic C/N atomic ratio, δ13Corg) were determined. Thereafter, KL was isolated from the samples, as the insoluble residue obtained after HF/HCl treatment. KL chemical composition was investigated via spectroscopic (FTIR, solid state 13C and 15N NMR) and pyrolytic (Curie point pyrolysis–gas chromatography–mass spectrometry) methods, and the morphological features were examined by scanning and transmission electron microscopy. Similar morphological features and chemical composition were observed for the three KLs and they suggested that the selective preservation of land-plant derived material as well as of resistant aliphatic biomacromolecules (probably derived from cell walls of freshwater microalgae) was the main process involved in KL formation. Besides, some melanoidin-type macromolecules (formed via the degradation-recondensation of products mainly derived from proteinaceous material) and/or some encapsulated proteins also contributed to the KL chemical structure.

Characterization of a highly resistant biomacromolecular material in the cell wall of a marine dinoflagellate resting cyst

The remarkable physical and chemical resistance of the organic cell walls enclosing resting cysts formed by several species of dinoflagellates has long invited questions regarding their composition. Traditionally, this resistance was thought to derive from the presence of “sporopollenin”, a term originally coined to describe the highly refractory substance found in the walls of pollen and spores of higher plants. The lack of detailed chemical analyses of dinoflagellate materials, however, has left this practice open to question. Here we report the results of the first rigorous chemical characterization of resting cyst walls produced by a dinoflagellate, the extant marine species Lingulodinium polyedrum (formerly Gonyaulax polyedra). Resistant cell walls were isolated by sequentially treating cyst-producing laboratory cultures by solvent extraction, saponification, and acid hydrolysis. At each stage of processing, residues were characterized by light microscopy, FTIR microspectroscopy, elemental analysis, and direct (“in source”) temperature–resolved mass spectrometry (DT–MS). Initial materials and final residues were further analyzed by Curie-point pyrolysis–gas chromatography–mass spectrometry (Py–GC/MS) and cupric oxide (CuO) oxidation. Overall, our results indicate an absence of extended n-hydrocarbon chains which typify aliphatic macromolecules (“algaenans”) dominating the resistant fractions of other algae studied to date. In contrast the data suggest that the cell wall contains relatively condensed, predominantly aromatic structures, possibly cross-linked via carbon–carbon or ether bonds. The presence of prist-1-ene among the most prominent pyrolysis products also suggests that bound tocopherols function as additional structural elements in the wall material(s). The L. polyedrum resting cyst cell wall thus appears to contain a biomacromolecular substance that is distinct from both sporopollenin and aliphatic algaenans. These findings help to further establish a chemical basis for the preservation potential of organic biomacromolecules, and illuminate possible chemical/functional relationships among highly refractory substances from diverse biological sources.