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PubMed2001

Ambient air quality at the site of a former manufactured gas plant.

Prior to the 1950's, manufactured gas was commercially produced from the pyrolysis of coal, coke, and oil at facilities that are termed manufactured gas plants (MGPs). The constituents of residual coal tar present on many MGP sites are an environmental health concern because of their toxicity and the possibility for their off-site migration via water and air. Atmospheric concentrations of five volatile organic compounds (VOCs, e.g., benzene), sixteen polycyclic aromatic hydrocarbons (PAHs, e.g., naphthalene) and particulate matter less than 10 microns in aerodynamic diameter (PM10) were measured at the site of a former MGP. Air samples were obtained before, during, and after excavation of subterranean coal tar at the site. The results of this investigation indicate that subterranean coal tar was not a primary source of VOCs and PAHs in the local atmosphere before or after remediation of the site. However, excavation, treatment, blending, and transfer of the coal tar during remediation generated concentrations of selected aromatic and semi-volatile organic compounds that were substantially greater than typical ambient levels. In addition, these data suggest that blending and mixing of coal tars could lead to exceedance of the U.S. National Ambient Air Quality Standard for PM10, although additional research is required to fully evaluate this possibility. Nuisance odors associated with the site remediation were likely the result of naphthalene and possibly isomers of xylene. Air pollutant concentrations measured adjacent to the excavation area and at the site perimeter during remediation activities were less than the relevant occupational and environmental exposure limits.

Air Pollution↗

PubMed2001

Hydroxyapatite implants with designed internal architecture.

Porous hydroxyapatite (HA) has been used as a bone graft material in the clinics for decades. Traditionally, the pores in these HAs are either obtained from the coralline exoskeletal patterns or from the embedded organic particles in the starting HA powder. Both processes offer very limited control on the pore structure. A new method for manufacturing porous HA with designed pore channels has been developed. This method is essentially a lost-mold technique with negative molds made with Stereolithography and a highly loaded curable HA suspension as the ceramic carrier. Implants with designed channels and connection patterns were first generated from a Computer-Aided-Design (CAD) software and Computer Tomography (CT) data. The negative images of the designs were used to build the molds on a stereolithography apparatus with epoxy resins. A 40 vol% HA suspension in propoxylated neopentyl glycol diacrylate (PNPGDA) and iso-bornyl acrylate (IBA) was formulated. HA suspension was cast into the epoxy molds and cured into solid at 85 degrees C. The molds and acrylate binders were removed by pyrolysis, followed by HA green body sintering. With this method, implants with six different channel designs were built successfully and the designed channels were reproduced in the sintered HA implants. The channels created in the sintered HA implants were between 366 microm and 968 microm in diameter with standard deviations of 50 microm or less. The porosity created by the channels were between 26% and 52%. The results show that HA implants with designed connection pattern and well controlled channel size can be built with the technique developed in this study.

Journal Article↗

PubMed1999

Kinetics and mechanism of St I modification by peroxyl radicals.

St I is a toxin present in the Caribbean Sea anemone Stichodactyla helianthus which is highly hemolytic in the nanomolar concentration range. Exposure of the toxin to free radicals produced in the pyrolysis of 2,2'-azobis(2-amidinopropane) hydrochloride leads to a progressive loss of hemolytic activity. This loss of hemolytic activity is accompanied by extensive modification of tryptophan residues. On the average, three tryptophan residues are modified by each inactivated toxin. The loss of hemolytic activity of St I takes place without significant changes in the protein structure, as evidenced by the similarity of the fluorescence and CD spectra of native and modified proteins. Also, the native and modified ensembles present a similar resistance to their denaturation by guanidinium chloride. The hemolytic behavior and the performance of the toxin at the single-channel level when incorporated to black lipid membranes suggest that the modified ensemble can be considered as composed of inactive toxins and active toxins whose behavior is similar to that of the native proteins. These results, together with the lack of induction time in the activity loss, suggest that the fall of hemolytic activity takes place by an all-or-nothing inactivation mechanism in which the molecules become inactive when a critical amino acid residue is modified.

Amino Acids↗

PubMed2003

Enzymatic synthesis of polyphenols from highly phenolic lignin-based polymers (lignophenols).

Peroxidase-catalyzed polymerization of lignin-based macromonomers (lignophenols), lignocatechol and lignocresol, prepared by phenolation of lignin with catechol or p-cresol, was carried out in aqueous organic solvent mixtures. The two lignophenols were polymerized to give cross-linked polymers. The highest yield of polymerization (83%, w/w) was obtained with lignocatechol, and the maximum yield for the polymerization of lignocresol was 55% (w/w). Pyrolysis GC-MS analysis of polymers indicated that the polymerization of lignophenols involved the oxidative coupling of the introduced phenol derivatives.

Catalysis↗

PubMed1979

Occurrence and significance of prist-1-ene in kerogen pyrolysates.

A SERIES of acylic isoprenoid alkanes, of which pristane and phytane are typical, frequently occurs in crude oils, shales, coals, bitumens and so on. It is generally agreed that the primary source of these compounds is the phytyl side chain of chlorophyll(1,2) although the mechanisms of its incorporation into sediments and its subsequent diagenesis, are not completely understood. At present, little is known about the role of kerogen as a source, or sink, of isoprenoid moieties and we report here that the principal isoprenoid, obtained by the high temperature (600 degrees C) pyrolysis of kerogens has been identified as prist-1-ene.

Journal Article↗

PubMed1982

Phencyclidine and phenylcyclohexene disposition after smoking phencyclidine.

Five men who smoked parsley cigarettes containing 100 micrograms of [3H]-phencyclidine hydrochloride (PCP.HCl) inhaled 69 +/- 5(SEM) % of the total radioactivity in the cigarette. Both PCP and its pyrolysis product, 1-phenylcyclohexene (PC), were found and measured in plasma. Calculations based on the assumption that the ratio of these two products was the same as in simulated smoking studies and based on either area under the curve or urinary excretion of PCP indicated that most of the PCP in smoke was absorbed. Mean half-life (t1/2) of PCP (24 +/- 7 hr, harmonic mean 18 hr) and ratios of metabolites in plasma and urine were close to those previously reported after intravenous and oral doses. A second peak in PCP plasma concentrations was observed, possible due to show efflux from the lungs. PC plasma concentrations (maximum 0.35 +/- 0.06 pmol/ml) were lower than those of PCP (maximum 0.62 +/- 0.09 pmol/ml) and its mean t1/2 (14 +/- 3 hr, harmonic mean 12 h) was shorter than that of PCP. Only traces of PC were found in urine. Only small amounts of metabolites from PC were found nonconjugated in plasma (to about 0.1 pmol/ml) or urine (less than 2% of radioactivity), but larger quantities were found as enzyme-hydrolyzable conjugates in urine (6% of radioactivity). Conjugates were also found in plasma (to about 0.12 pmol/ml).

Adult↗

PubMed2004

Complex organic chemical balms of Pharaonic animal mummies.

Millions of votive mummies of mammals, birds and reptiles were produced throughout ancient Egypt, with their popularity increasing during the reign of Amenhotep III (1400 bc) and thereafter. The scale of production has been taken to indicate that relatively little care and expense was involved in their preparation compared with human mummies. The accepted view is that animals were merely wrapped in coarse linen bandages and/or dipped in 'resin' before death. However, as with human mummification there was a range of qualities of treatments, and visual inspection of animal mummies suggests that the procedures used were often as complex as those used in humans (for example, evisceration and elaborate bandaging). Moreover, the ancient Egyptians treated animals with great respect, regarding them both as domestic pets and representatives of the gods; for example, the cat symbolized the goddess Bastet; the hawk, Horus; the ibis, Thoth, and so on. We report here the results of chemical investigations of tissues and wrappings from Pharaonic cat, hawk and ibis mummies using gas chromatography, gas chromatography-mass spectrometry, thermal desorption-gas chromatography-mass spectrometry and pyrolysis-gas chromatography-mass spectrometry. The analyses reveal the presence of highly complex mixtures of n-alkyl and cyclic biomarker components characteristic of fats, oils, beeswax, sugar gum, petroleum bitumen, and coniferous, Pistacia and possibly cedar resins. The mixture of balms is of comparable complexity to those used to mummify humans from the same period.

Animals↗

PubMed2006

Astrochemistry: Complex organic matter in Titan's aerosols?

On 14 January 2005, the Huygens probe entered the atmosphere of Titan after a seven-year interplanetary flight as part of the Cassini mission to Saturn. Huygens carried, among other instruments, an aerosol collection and pyrolysis (ACP) device. Its designers, Israël et al., now claim to have detected complex organic matter in two aerosol samples collected at different altitudes (130-35 km and 25-20 km, respectively), on the basis of their detection of ammonia (NH3) and hydrogen cyanide (HCN) when the sample oven was heated to 600 degrees C. However, the authors' remarkable conclusions, which would have far-reaching consequences for our understanding of the chemical environment prevailing on Saturn's largest moon, are not supported by their limited data.

Comment↗

PubMed2004

Probing the dynamics of nanoparticle growth in a flame using synchrotron radiation.

Flame synthesis is one of the most versatile and promising technologies for large-scale production of nanoscale materials. Pyrolysis has recently been shown to be a useful route for the production of single-walled nanotubes, quantum dots and a wide variety of nanostructured ceramic oxides for catalysis and electrochemical applications. An understanding of the mechanisms of nanostructural growth in flames has been hampered by a lack of direct observations of particle growth, owing to high temperatures (2,000 K), rapid kinetics (submillisecond scale), dilute growth conditions (10(-6) volume fraction) and optical emission of synthetic flames. Here we report the first successful in situ study of nanoparticle growth in a flame using synchrotron X-ray scattering. The results indicate that simple growth models, first derived for colloidal synthesis, can be used to facilitate our understanding of flame synthesis. Further, the results indicate the feasibility of studies of nanometre-scale aerosols of toxicological and environmental concern.

Journal Article↗

PubMed2002

Large-area synthesis of carbon nanofibres at room temperature.

Carbon nanotubes, first identified by Iijima, require for their production a source of elemental carbon and a transfer of energy that is specific to the type of source and the growth environment. Methods developed so far involve arc discharge, and vaporization using laser, pyrolysis and chemical vapour deposition of hydrocarbons. Here, we show growth of carbon nanofibres from radio-frequency plasma-enhanced chemical vapour deposition at room temperature, which was made possible by substituting the thermal energy requirements for the growth with plasma decomposition of methane on the Ni catalyst. Electron microscopy analysis provides evidence for a 'tip' growth model, with the Ni catalyst particle attached to the tip of the nanofibre. Energy-filtered imaging shows the Ni catalyst has a surface layer rich in carbon, consistent with the formation of a eutectic Ni-C droplet as a nucleation site for the carbon nanofibres, so that the carbon diffuses across the surface. The reduced distortion of the catalyst particles at low temperatures leads to a more uniform growth of the carbon nanofibres over large areas. The lower growth temperature allows for the removal of the silicon dioxide barrier layer associated with catalytic growth, and should allow in situ growth of nanofibres on relatively large areas of temperature-sensitive substrates, such as plastics, organics and even paper.

Diffusion↗

PubMed1999

Assessment of occupational exposure to diesel fumes--parameter optimization of the thermal coulometric measurement method for carbon.

'Elemental' carbon (EC) is used as a surrogate to assess occupational exposure to diesel soot. EC thermal analysis needs complete desorption of organic compounds from the soot particles prior to analysis in order to minimize positive interferences and artefacts. The desorption of the organic compounds can be considered as the major step which influences the reliability of the EC determination. A systematic study was carried out to investigate the different parameters of influence such as desorption temperature, desorption duration, heating rate and type of the sample on the desorption efficiency. It was found that temperature and duration are the major parameters of influence on the desorption efficiency. The influence of the sample load can be seen as a measure of the pyrolysis susceptibility of the sample. An optimized temperature program is proposed.

Carbon↗

PubMed2000

Analysis of sediments from Shetland Island voes for polycyclic aromatic hydrocarbons, steranes and triterpanes.

A few days after the grounding of the oil tanker Braer on 5 January 1993, an Exclusion Zone was designated by Order under the Food and Environment Protection Act 1985, prohibiting the harvesting of farmed or wild shellfish within the Zone to prevent contaminated products reaching the market place. The order was progressively lifted for species that were found to be free of petrogenic taint and for which the polycyclic aromatic hydrocarbon (PAH) levels were within the range for reference samples. This Order, however, still remains in place for mussels (Mytilus edulis) as the PAH levels are higher than in reference mussels. To investigate the possible source of PAHs found in these mussels, sediments were collected from three reference and three Zone sites and their hydrocarbon compositions studied using the n-alkane composition and concentration, PAH composition and concentration and the sterane and triterpane composition. The reference site at Olna Firth was found to have the highest levels of 2-6-ring parent and branched PAHs, the highest concentration in one of the pooled sediments being 4,530 ng g(-1) dry weight. Values in the other two reference sites (Vaila Sound and Mangaster Voe) ranged from 248.7 to 902.2 ng g(-1) dry weight. PAH concentrations at the Zone sites (Sandsound Voe, Stromness Voe and Punds Voe) ranged from 641.0 to 2,766 ng g(-1) dry weight. The PAH data were normalised to the percentage of organic carbon and log-transformed prior to being analysed using principal component analysis. The mean total PAH concentrations for Zone sites were found not to be significantly different from the reference sites. The PAH concentration ratios were consistent with the main source of PAHs being pyrolysis. However, there was a petrogenic contribution, suggested by the presence of alkylated PAHs, with Punds Voe having the largest petrogenic hydrocarbon content. This was supported by the triterpane profiles and the presence of a UCM in the aliphatic chromatograms from Punds Voe sediments.

Animals↗

PubMed2000

Structural characterisation of macromolecular organic material in air particulate matter using Py-GC-MS and solid state 13C-NMR.

Organic air particulate matter was analysed by applying the techniques of Py-GC-MS (pyrolysis-gas chromatography-mass spectrometry) and solid state 13C-NMR (nuclear magnetic resonance). Particles dislodged from air particulate filters and humic acid extracted from these filters were studied for structural components. The structural components of the air particles and extracted humic acid consisted of compounds originating from biomacromolecules, namely, lignin, carbohydrates, protein and lipids. The main components identified for each class included: (1) methoxyphenols originating from lignin; (2) furans, aldehydes and ketones from carbohydrates; (3) pyrrole, indoles from protein; and (4) many hydrocarbons from lipid structures. Single ion monitoring (SIM) and tetramethyl ammonium hydroxide (TMAH) methylation were utilised for detection of aliphatic hydrocarbons and acidic components, respectively. Hydrocarbons ranging from C9 to C28 were detected by SIM analysis, while aliphatic acids ranged from C9 to C18. The majority of components analysed directly in the air particles were similar to those from the humic acid extracts. Many of the structural components of air particles were typical of humic substances of soil and aqueous systems and these were attributed to both biogenic and anthropogenic sources.

Air Pollution↗

PubMed2001

Determination of tellurium in indium antimonide semiconductor material by electrothermal atomic absorption spectrometry.

A method for the determination of the dopant concentration of tellurium in dissolved indium antimonide semiconductor material by electrothermal atomic absorption spectrometry (ETAAS) was developed. Efforts were made to investigate the optimal conditions of the furnace heating program and the effect of palladium modifier on the variation of tellurium and the background absorbance. According to the results obtained, the presence of palladium chemical modifier in the analysis of indium antimonide allowed the successful retention of tellurium in the graphite tube, and the optimum mass of palladium modifier was found to be dependent on the sample matrix concentration. The absorbance profile of tellurium and the background level were significantly improved when a pyrolysis temperature of 1100 degrees C and an atomization temperature of 2200 degrees C were employed in the optimized heating program. With the use of this method, a detection limit of 0.8 microg g(-1) tellurium in indium antimonide could be achieved. The applicability of the proposed method was evaluated by comparison with two independent methods, i.e. slurry sampling-ETAAS and ICP-MS. From the good agreement between the results, it was demonstrated that the proposed method is suitable for the determination of typical dopant concentrations of tellurium in indium antimonide.

Journal Article↗

PubMed2001

Reactions of methyl radicals with propene at temperatures between 750 and 1000 K.

The pyrolysis of propene, initiated by methyl radicals, has been studied in the temperature range 750-1000 K and at a pressure of 0.13 bar in a quasi-wall-free reactor using laser heating by fast vibrational-translational (V-T) energy transfer. This is a convenient method to study homogeneous high-temperature kinetics since the reactor walls remain cold. The radial temperature distribution in the reactor has been investigated by four different methods: a stationary heat balance, optical absorption, pressure rise, and the temperature dependence of the rate of an isomerization reaction. Methyl radicals were produced via the fast thermal dissociation of di-tert-butyl-peroxide and the products were analysed using GC-MS. The main products of the overall reaction of the model system propene and methyl (C3H6 + CH3) were isopentane (iso-C5H12) and but-1-ene (1-C4H8), whereas allene (C3H4), trans-but-2-ene (trans-2-C4H8) and cis-but-2-ene (cis-2-C4H8) were minor components, all showing a strong dependence on temperature. The product distribution and the temperature dependence were analysed by a kinetic model of 61 species and 166 reactions developed for the high-temperature oxidation of butane and the low-temperature oxidation of n-pentane and isopentane. It was necessary to include a few missing reactions and to adjust some rate constants to make the modeling agree with the experimental investigations. This extended mechanism has to be evaluated further in forthcoming experiments.

Journal Article↗

PubMed2001

A new stabilised form of isobenzofuran, rack-mounted on an alicyclophane.

New stable, crystalline isobenzofurans 9a and 9b linked through the 1,3-positions and incorporated into alicyclophanes have been prepared from the related furanoalicyclophane 5 in three steps (i) addition of benzyne or 4,5-bis(trimethylsilyl)benzyne (ii) hydrogenation of the pi-bond (iii) ejection of ethylene by flash vacuum pyrolysis, and shown to yet retain high 1,3-diene character and form adducts with dienophiles, e.g. dimethyl acetylenedicarboxylate or N-methyl maleimide; the corresponding off-rack 1,3-dimethylisobenzofurans were too unstable for isolation.

Journal Article↗

PubMed2002

Evaluation and application of bismuth as an internal standard for the determination of lead in wines by simultaneous electrothermal atomic absorption spectrometry.

A method for the direct determination of Pb in wines by simultaneous multi-element atomic absorption spectrometry (SIMAAS) using a transversely heated graphite atomizer, Zeeman-effect background corrector and internal standardization is proposed. Bismuth was used as an internal standard and Pd(NO3)2 plus Mg(NO3)2 as chemical modifier to stabilize both the analyte and the internal standard. The implementation of two pyrolysis steps avoided any build-up of carbonaceous residues on the graphite platform. All diluted samples (1 + 1 v/v) in 0.2% v/v HNO3 and reference solutions (5.0-50 microg l(-1) Pb in 0.2% v/v HNO3) were spiked with 25 microg l(-1) Bi. For a 20 microl aliquot dispensed into the graphite tube, a good correlation (r = 0.9997) was obtained between the ratio of the analyte signal to the internal standard signal and the analyte concentration of the reference solutions. The electrothermal behaviour of Pb and Bi in red, white and rosé wines were compared. In addition, absorbance variations due to changes in experimental conditions, such as atomizer temperature, integration time, injected sample volume, radiation beam intensity, graphite tube surface, dilution and sample composition, were minimized by using Bi as internal standard. Relative standard deviations of measurements based on integrated absorbance varied from 0.1 to 3.4% and from 0.5 to 7.3% (n = 12) with and without internal standard correction, respectively. Good recoveries (91-104%) for Pb spikes were obtained. The characteristic mass was 45 pg Pb and the limit of detection based on integrated absorbance was 0.9 microg l(-1) Pb. Internal standardization increased the lifetime of the tube by 25%. Direct determinations of Pb in wines with and without internal standardization approaches were in agreement at the 95% confidence level. The repeatability and the tube lifetime were improved when using Bi as internal standard. The improvement in accuracy using an internal standard was only observed when the analytical results were affected by errors.

Bismuth↗

PubMed2001

The polycyclic aromatic hydrocarbon and geochemical biomarker composition of sediments from voes and coastal areas in the Shetland and Orkney Islands.

Marine sediments from coastal areas and voes in the Shetland and Orkney Islands were analysed for parent and branched 2- to 6-ring polycyclic aromatic hydrocarbons (PAHs) and geochemical biomarkers. Where possible 14 sediment samples were collected at random from each of 17 Shetland and 9 Orkney sites. The wide range of total PAH concentrations in sediments (i.e., < LOD up to 22619 ng g(-1) dry weight) was indicative of a variety of anthropogenic activities and different sediment types associated with the specific locations. Low PAH concentrations were determined in sandy sediments from areas of limited boat activity. The highest PAH concentrations were found in muddy sediment close to a boat repair yard. PAH concentration ratios were consistent with the main source of these compounds, in most areas, being pyrolysis. Geochemical biomarker (triterpane and sterane) profiles from the sediment were indicative, for some areas, of limited petrogenic input. Punds Voe was the only voe to show evidence of North Sea oil. PAH profiles were similar across sites within each island group, with any differences attributable to known local sources of PAHs. However, there was a clear difference in the PAH profiles of Shetland and Orkney sediments, with Orkney sediments having a higher proportion of the lighter alkylated PAHs.

Environmental Monitoring↗