Margriet Nip

Analysis of modern and fossil plant cuticles by Curie point Py-GC and Curie point Py-GC-MS: recognition of a new, highly aliphatic and resistant biopolymer

Abstract This paper investigates to what extent the chemical constituents of plant cuticles (waxes and cutin) can survive diagenesis. Recent and fossil plant cuticles were analyzed by means of Curie point pyrolysis-gas chromatography and Curie point pyrolysis-gas chromatography-mass spectrometry. Recent cuticles were analyzed without treatment, after solvent extraction and after cutin depolymerization. Extensive series of straight-chain alkanes, alk-1-enes and α,ω)-alkadienes dominate the pyrolysates, especially after removal of the wax and cutin. 13 C-NMR spectroscopy of the residue after removal of the cutin confirmed the presence of a new, highly aliphatic biopolymer and a polysaccharide fraction. The abundance of straight-chain alkanes, alk-1-enes and α,ω-alkadienes in the fossil plant cuticles indicates the chemical resistence of the biopolymer to diagenesis and may explain the occurrence of straight-chain aliphatic moieties in organic-matter-rich sediments and coals as revealed by “C-NMR spectroscopy and flash pyrolysis methods. The highly aliphatic biopolymer may function as an important oil precursor.

A new non-saponifiable highly aliphatic and resistant biopolymer in plant cuticles

Analysis of present-day plant cuticles by flash pyrolysis methods revealed the presence of a previously unknown, non-saponifiable highly aliphatic biopolymer. Its occurrence in fossil plant cuticles suggests a high chemical resistance towards diagenesis and offers a clue to the unraveling of the chemical nature of the coal maceral cutinite. p lant cuticles are thin, continuous extracellular layers which cover the outer surface of the aerial parts of plants. Their occurrence is ubiquitous and their role as contributors to the organic matter in sediments and coals may be very important. It is generally agreed that the chief chemical components of plant cuticles are lipids, the insoluble high-molecular-weight polyester cutins that form the structural framework of the membrane with soluble waxes embedded within it and secreted onto its surface. However, analysis of recent and fossil plant cuticles by flash pyrolysis techniques has revealed the existence of a previously unknown, non-saponifiable highly aliphatic and chemically resistant biopolymer. This biopolymer represents a significant proportion of the biomass of some present-day and several fossil plant cuticles. To verify the possibility that the maceral cutinite of coals originates from plant cuticles, we have recently investigated a number of fossilized cuticles. Because the organic matter in these cuticles is present almost exclusively in the polymeric state, Curie-point pyrolysis coupled with gas chromatography (Py-GC) and mass spectrometry (Py-GCMS) were chosen as the primary methods of analysis. Such techniques have already been shown to be extremely useful in the identification and structurai elucidation of a wide range of natural and synthetic polymeric materials.

Scope and limitations of several pyrolysis methods in the structural elucidation of a macromolecular plant constituent in the leaf cuticle of Agave americana L.

Abstract Cuticles of Agave americana contain a substantial amount of an insoluble, non-hydrolyzable macromolecular substance of a highly aliphatic nature. Based on Fourier transform infrared (FTIR) and 13 C cross-polarization magic angle spinning NMR spectroscopy it was established that the isolated macromolecular substance consists of a polysaccharide and polymethylene moiety in an estimated ratio of 60:40 by weight. After treatment with acid this ratio changed to 37: 63. The isolates obtained before and after the acid treatment were subjected to Curie-point pyrolysis-gas chromatography with flame ionization detection, Curie-point pyrolysis-gas chromatography/mass spectrometry, Off-line pyrolysis in combination with gas chromatography and gas chromatography/mass spectrometry, desorption chemical ionisation mass spectrometry, time/temperature-resolved pyrolysis-field ionization mass spectrometry and heating experiments in a closed system in order to elucidate the molecular structure. Each of the methods applied has its own specifications with respect to pyrolysis conditions and response factors of different classes of pyrolysis products. The data obtained are highly complementary and, in combination with FTIR and 13 C NMR, several new features of the insoluble, non-hydrolyzable aliphatic biopolymer were revealed.

Identification of some sulphur species in a high organic sulphur coal

Abstract In this paper, a preliminary study is described concerning the characterization of sulphur forms in a subbituminous coal rich with organic sulphur deposited in a lacustrine carbonate environment (Upper Cretaceous, Provence, France). Two American high organic sulphur coals were studied for comparison with the Provence coal. Optical microscopy, scanning electron microscopy and electron microprobe approaches offered a global view of the relations between sulphur, metals and coal petrography. Sulphur occurs in all the macerals and most minerals. Vitrinite contains the major part of organic sulphur and metals. This common occurrence of organic sulphur and metals in vitrinite suggests the presence of organosulphur-metallic species. X-Ray photoelectron spectrometry showed that mineral and organic sulphur is very much reduced (divalent). It would mainly include pyrite, sulphides and thiophenes. Programmed temperature oxidation and programmed temperature reduction (Attars test) revealed fragile sulphur compounds such as aliphatic thiols and sulphides and thermal stable sulphur compounds such as aromatic and high molecular weight compounds. Curie-point pyrolysis in combination with mass spectrometry, gas chromatography, and gas chromatography-mass spectrometry indicated the absence of free organic sulphur compounds and of elemental sulphur. Pyrolysis yielded large amounts of low molecular weight products (H 2 S, COS, etc.) and smaller amounts of thiopenes, benzothiophenes, dibenzothiophenes and their alkylated homologues. These sulphur compounds could result from the thermal degradation of organic sulphur moieties of the coal as well as from secondary reactions.

A flash pyrolysis and petrographic study of cutinite from the Indiana paper coal

Abstract Samples obtained from the high-volatile bituminous Indiana cuticle-rich and paper coals (Indiana U.S.A.) were investigated by white light and blue light microscopy and by Curie point pyrolysis-mass spectrometry in combination with multivariate data analysis, Curie point pyrolysis-gas chromatography and Curie point pyrolysis-gas chromatographymass spectrometry. Samples obtained from several sites and of different degrees of weathering were analyzed. The macerai cutinite from the same samples was studied as well. The cutinite was concentrated by a standard palynological chemical oxidation technique as well as by density gradient centrifugation. The major constituent of the Indiana paper coal samples appeared to be a recently discovered non-saponifiable polymethylenic biopolymer, present in both recent and fossil plant cuticles. The maceral cutinite is almost exclusively made up of this highly resistant biopolymer. It is shown that upon severe natural weathering this biopolymer, because of its resistance against organic alteration and diagenesis, is relatively enriched and manifests itself in humic coals as the maceral cutinite.

The characterization of eight maceral concentrates by means of Curie point pyrolysis-gas chromatography and Curie point pyrolysis-gas chromatography-mass spectrometry

Abstract In order to study the relationships between the chemical structures of coals, coal macerals and their precursors (plant tissues), eight coal macerals originating from the Yorkshire coal basin (U.K.) were studied by Curie point pyrolysis-gas chromatography and Curie point pyrolysis-gas chromatography-mass spectrometry. The samples were selected on the basis of a previous study of a large set of macerals. The macerals were studied in order to relate structural moieties of the macerals, as reflected by their pyrolysis products, to structural elements of their likely precursors, plant tissues. The maceral pyrolysates mainly consist of alkylbenzenes, alkylnaphthalenes, alkylphenols and series of straight-chain alk-l-enes and alkanes over a wide molecular weight range. The relative contribution of the (hydroxy)aromatic pyrolysis products and of the straight-chain alk-l-enes and alkanes to each maceral pyrolysate was calculated, although the internal distribution patterns of the alkyl derivatives of these pyrolysis products exhibited to a certain extent dissimilarities. Differences between the relative contributions of these pyrolysis products to the pyrolysates of different macerals with the same coal rank and to those of similar macerals with different coal rank depend on differences in precursor material and the chemical modification of these precursors upon increasing coalification. Multivariate data treatment by means of factor analysis was chosen to compare the pyrolysis data—represented by these histograms—with the petrographic data and the proximate and ultimate analysis values of the macerals. In addition, similar analyses was performed on the macerals using such a low Curie temperature (358°C), that from some of the macerals “thermal extracts” were obtained, containing a series of n -alkanes and some isoprenoids such as pristane and phytane. Although these thermal extracts represent only a low percentage by weight of the maceral samples, their existence probably will affect both the chemical and physical properties of the macerals, although they are in fact no pan of the coal structure itself.

Comparison of flash pyrolysis, differential scanning calorimetry, 13C NMR and IR spectroscopy in the analysis of a highly aliphatic biopolymer from plant cuticles

Abstract Recently we described the occurrence of a highly aliphatic and resistant biopolymer in leaf cuticles of some modern and fossil higher plants. The highly aliphatic nature of this biopolymer was deduced from flash pyrolysis-gas chromatographic and flash pyrolysis-gas chromatographic-mass spectrometric data. In an attempt to further identify its molecular structure, a “purified” fraction of the biopolymer was subjected to solid state 13 C NMR and IR spectroscopy, differential scanning calorimetry and elemental analysis. Surprisingly the 13 C NMR data indicated that ca. 50% of the sample consists of carbohydrate moieties and that the remainder can be ascribed to the expected polyethylene moieties. The IR and differential scanning calorimetry data were in accordance with these 13 C NMR data as well as the elemental analysis. The cross-polarization behaviour during the 13 C NMR experiments and the percentage of crystallinity in both the polyethylene and the saccharide moiety (ca. 50%) are indicative of covalent bonds between the two. This was further supported by additional density scanning calorimetric and flash pyrolysis-gas chromatographic analyses. Obviously analysis of the aliphatic biopolymer by flash pyrolysis alone was highly misleading since the pyrolysate only reflected a limited and specific part of the macromolecular structure. This investigation very clearly demonstrates that analytical pyrolysis should be used only in combination with other analytical methods, especially solid state 13 C NMR and IR spectroscopy, to elucidate the molecular substructures of insoluble macromolecular or polymeric compounds.

Curie-point pyrolysis mass spectrometry, Curie-point pyrolysis-gas chromatography-mass spectrometry and fluorescence microscopy as analytical tools for the characterization of two uncommon lignites

Abstract A case study is presented of two uncommon lignite samples, PSOC-975 and PSOC-427, which were studied by microscopic and analytical pyrolysis methods. Pyrolysis-mass spectrometric (Py-MS), pyrolysis-gas chromatographic (Py-GC) and Py-GC-MS data demonstrate that lignite PSOC-975 contains a high abundance of resinous material of some sort, whereas PSOC-427 is characterized by two major unknown pyrolysis products, prist-1-ene and alkylphenols. The chemical data contradict the microscopic observations, which point to a maceral composition of woody and cortical tissues, although a considerable part is unrecognizable. Apparent discrepancies between low-voltage Py-MS and 80-eV Py-GC-MS results were evaluated by a study of standards. It was shown that the aliphatic hydrocarbons are highly underestimated in low-voltage Py-MS. The nature of the disagreement observed between maceral composition and the pyrolysis data needs further study.

Gelatinous pellicles in deep anoxic hypersaline basins from the Eastern Mediterranean

Abstract Gelatinous pellicles have been observed in three out of ten cores recovered from the Bannock Basin (or Bacino Bannock) and in two dredges from its flanks during a cruise of the R.V. Bannock in the Eastern Mediterranean. Similar pellicles have also been detected in two cores recovered from the Tyro Basin. The Bannock and Tyro basins are brine-filled depressions which are presently characterized by anoxic sedimentation; in the Bannock Basin also gypsum precipitation occurs. The gelatinous pellicles, some millimeters thick and dark grey to greenish in color, are always found in very dark colored sediments of Quaternary age. These pellicles have been investigated by optical microscopy, by scanning electron and transmission electron microscopy, and by flash pyrolysis-gas chromatography and flash pyrolysis-gas chromatography-mass spectrometry to decipher their nature. Abundant skeletal tests of siliceous and calcareous planktonic organisms (radiolaria, diatoms, silicoflagellates, formainifera and nannofossils) are observed, together with amorphous organic matter. The pellicles enclosing these remains consist of organic matter; they foliate into submillimetric undulating and anastomosing microlaminae. Cellular structures are never observed, neither in the pellicles nor in the microlaminae. Organic geochemical analyses point to a high contribution of terrestrial material. The organic matter of the pellicles investigated consists of a “coal-like” material. It is suggested that the pellicles are originally formed at the brine-seawater interface, but subsequently sink to the bottom due to increasing load of entrapped biogenic and non-biogenic detritus.

Chemical characterization of Hungarian brown coals by curie-point pyrolysis-low-energy electron impact mass spectrometry and multivariate analysis and by curie-point pyrolysis-gas chromatography-photoionization mass spectrometry

Abstract A series of Hungarian Miocene brown coals were analysed by pyrolysis-low-energy electron impact mass spectrometry and discriminant analysis. Correlation patterns in the mass peaks of these brown coals coincided with the geothermal history determined from the reflectivity of the macerals. Coal rank and the first discriminant function had a correlation coefficient of 0.96. Discriminant analysis also classified the coals according to their depositional environment. The mass peaks were deconvoluted using pyrolysis-gas chromatography-mass spectrometry data obtained under low-energy photoionization conditions. Several apparently homologous series of mass peaks in the pyrolysis-low-energy electron impact mass spectra were found to represent entirely different types of pyrolysis products. The low-energy fragmentation patterns of isoprenoid and alicyclic hydrocarbons are substantially different from the usual 70 eV electron impact spectra and may cause erroneous interpretation of non-deconvoluted pyrolysis-low-energy electron impact mass spectrometric data. The deconvoluted pyrolysis-low-energy electron impact mass spectrometric data resulted in a more detailed reconstruction of the original environments of deposition. Marine influences were deduced from several types of organic sulphur compounds. Markers for lignified wood, leaf and root remains and resins were present in the pyrolysates.