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PubMed1991

Isolation and structural determination of a mutagenic substance in creatine pyrolysate.

The pyrolysis product of creatine showed potent mutagenic activity to Salmonella typhimurium TA98 with metabolic activation by S9 mix. One of the mutagenic substances in creatine pyrolysate was isolated and named Cre-P-1. Its structure was determined by X-ray crystallography to be 4-amino-1,6-dimethyl-2-methylamino-1H,6H-pyrrolo[3,4-f]benzimidazole- 5,7-dione. Cre-P-1 is the first registered mutagenic heterocyclic amine containing oxygen atoms in the molecule, that has been isolated from pyrolysis products.

Animals↗

PubMed2005

[Cascade reactions of unsaturated xanthates and related reactions: computer-assisted molecular design and analysis of reaction mechanisms].

Chugaev reaction provides access to olefins from alcohols without rearrangement through pyrolysis of O-alkyl S-alkyl dithiocarbonates (xanthates) via cis elimination. Xanthates having no beta-hydrogens undergo thione-to-thiol rearrangement to give S,S-dialkyl dithiocarbonates (thiolcarbonates). Based on these backgrounds, we intended to use the dithiolcarbonates as precursors of thiols. Xanthates could be converted to the corresponding dithiolcarbonates by Lewis-acid catalysis. Pyridine N-oxides and 4-dimethylaminopyridine also catalyzed the rearrangement reaction. On the other hand, O-(2-alkenyl) S-alkyl dithiocarbonates undergo [3,3]-sigmatropic rearrangement to give the allylically rearranged S-(2-alkenyl) S-alkyl dithiocarbonates. The homoallylic xanthates gave the corresponding dithiolcarbonates on heating with phenols. Pyrolysis of allylic dithiolcarbonates caused retro-ene type reaction to give the allylic sulfides in which allylic rearrangement also occurs. Coupling of these pericyclic reactions with intramolecular Diels-Alder reaction affords a one-pot synthetic method for the construction of hydroisobenzothiophenes. The mechanisms of the cascade and related reactions are demonstrated by location of the transition states using molecular orbital calculation method at various levels of theory involving density functional theory (DFT).

Chemistry, Organic↗

PubMed1976

Chemistry of rubber processing and disposal.

The major chemical changes during the processing of rubber occur with the breakdown in mastication and during vulcanization of the molded tire. There is little chemical change during the compounding, calendering, extrusion, and molding steps. Reclaiming is the process of converting scrap rubber into an unsaturated, processible product that can be vulcanized with sulfur. Pyrolysis of scrap rubber yields a complex mixture of liquids, gas, and residue in varying ratios dependent on the nature of the scrap and the conditions of pyrolysis.

Carbon↗

PubMed2006

The BTL2 process of biomass utilization entrained-flow gasification of pyrolyzed biomass slurries.

Forschungszentrum Karlsruhe has developed a concept for the utilization of cereal straw and other thin-walled biomass with high ash content. The concept consists of a regional step (drying, chopping, flash-pyrolysis, and mixing) and a central one (pressurized entrained-flow gasification, gas cleaning, synthesis of fuel, and production of byproducts). The purpose of the regional plant is to prepare the biomass by minimizing its volume and producing a stable and safe storage and transport form. In the central gasifier, the pyrolysis products are converted into syngas. The syngas is tar-free and can be used for Fischer-Tropsch synthesis after gas cleaning.

Biomass↗

PubMed1999

Economic analysis of selected lignocellulose-to-ethanol conversion technologies.

The objective of this case study was to examine the economics of three lignocellulose-to-ethanol conversion technologies: fast pyrolysis integrated with a fermentation step, simultaneous saccharification and fermentation (SSF), and dilute sulfuric acid hydrolysis and fermentation. All technologies were assumed to have an annual production rate of 25 million gallons of ethanol. The three technologies were compared in terms of capital costs, operating costs, and ethanol production costs. Sensitivity analyses were carried out to study the uncertainties of wood costs and ethanol production rates on ethanol production costs. Final economic analysis showed that fast pyrolysis integrated with a fermentation step is comparable with the other two processes and suggests that it should be considered for further development.

Journal Article↗

PubMed1986

Volatile organic acids generated from kerogen during laboratory heating.

Low molecular weight organic acids were studied in the course of pyrolysis experiments (200-400 degrees C, 2-1,000 h) of kerogen (Green River Formation and Monterey Formation) with and without the presence of water and minerals (montmorillonite, illite and calcite). C1-C10 aliphatic acids and benzoic acid were identified in the pyrolysis products of kerogen. Their distribution is characterized by a dominance of acetic acid followed by formic and propionic acids with an even/odd preference in the range of C4-C10. Total concentrations of these acids amounted to 0.3% of initial kerogen, indicating that kerogen has a good potential for producing organic acids. Geochemical implications of these organic acids are; (1) they are possible intermediates from kerogen to natural gas (CO2, H2, CH4, C2H6, etc.) by decarboxylation, and (2) they may be important and potential contributors to the generation of secondary porosity by dissolving minerals.

Aluminum Silicates↗

PubMed1975

Metabolism of nicotine by the isolated perfused dog lung.

1. Metabolism of [14C]nicotine has been studied in the isolated perfused dog lung. [14C]Nicotine, 50 mug every 30 s for 10 min administered via the pulmonary artery, undergoes first pass metabolism to a small extent. [14C]Cotinine was detected in the venous blood. Of the injected activity, 6 percent was in the lung at the end of experiment; 60 percent being present as [14C]nicotine and 20 percent as [14C]nicotine-1'-oxide. 2. When [14C]nicotine was administered in cigarette smoke a greater degree of metabolism was observed at first pass. Pyrolysis products of [14C]nicotine also were present in the venous blood. Lungs after smoke exposure contained 30 percent of administered radioactivity, with a substantial proportion of [14C]nicotine-1'-oxide. 3. Administration of [14C]nicotine-labelled smoke to lung preparations, on closed circuit, gave significant amounts of [14C]cotinine and other metabolites over a 2 h period. Lung tissue contained approx. 40 percent of injected dose, of which 25 percent only was [14C]nicotine. Large proportions of [14C]cotinine and [14C]nicotine-1'-oxide were present but 45 percent of the activity was present as other unidentified pyrolysis products. [14C]Demethyl cotinine was detected.

Animals↗

PubMed1993

Free radical formation induced by ultrasound and its effects on strand breaks in DNA of cultured FM3A cells.

Recent sonochemical studies have revealed that active oxygen species are formed by pyrolysis of water molecules due to high temperature cavitation bubbles. When aqueous solutions of DNA were sonicated, single-strand breaks and double-strand breaks of DNA were observed. Formation of double-strand breaks due to mechanical effects of cavitation and formation of single-strand breaks mostly due to free radicals were indicated. The sonochemically generated radicals from DNA constituents due to H atom and OH radical reactions, and pyrolysis processes, were identified by spin trapping with 3,5-dibromo-2,6-dideuterio-4-nitrosobenzene sulfonate. When suspensions of mouse mammary carcinoma FM3A cells and aqueous solutions of 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) were exposed to 1 MHz ultrasound in the presence of Ar, a good correlation between DMPO-OH formation and the cell killing induced by ultrasound were observed. Although single-strand breaks of DNA in the cells were observed at the maximum intensity of DMPO-OH formation and cell killing, double-strand breaks were not. Free radical formation by ultrasound in aqueous solutions and its relation to DNA strand breaks in vitro and in vivo are discussed.

Animals↗

PubMed1994

Bladder cancer and occupational exposures.

OBJECTIVES: A hospital-based case-referent study was carried out in Lyon with the purpose of generating hypotheses about the role of occupational exposures to 320 compounds in bladder carcinogenesis. METHODS: Job histories were obtained by questionnaire for 116 cases and 232 reference patients with diseases other than cancer (one referent from the same hospital ward and one from another ward of the same hospital per case); the referents were matched for gender, hospital, age, and nationality. Systematic coding of exposures, with a blind analysis of job histories, was carried out by a team of experts in chemistry and occupational health. RESULTS: Significantly elevated odds ratios were observed for exposure to pyrolysis and combustion products [odds ratio (OR) 2.3, 95% confidence interval (95% CI) 1.0-4.0] when the general referents were used and for cutting fluids (OR 2.6, 95% CI 1.2-5.4) when tobacco consumption was adjusted for. The latter was highest among the category consisting of blue-collar and unskilled workers, supervisors, and agricultural workers (OR 4.6 95% CI 2.0-10.6), while the odds ratio for the other category was 0.8 (95% CI 0.3-2.7). An elevated odds ratio for exposure to inks was observed for the women (OR 14.0, 95% CI 1.8-106.5) on the basis of 14 exposed cases, but confounding factors could have been responsible for this result. Odds ratios for several other exposures (rubber: OR 5.7, nitrates: OR 8.2, coke dust: OR 3.5, meat additives: OR 3.8) were also elevated, but not significantly so when based on a small number of exposed cases. CONCLUSION: The observations of this investigation should be tested in future studies, in particular since exposures to agents such as cutting fluids or pyrolysis products are ubiquitous in industrial settings and may present an important public health hazard.

Adult↗

PubMed1999

Molecular composition of the louse sheath.

Flash pyrolysis-gas chromatography/mass spectrometry was used to assess the chemical composition of the head louse's nit sheath. The pyrolyzate of the female insect's secretions, which form a cement-like cylinder holding the egg onto the hair, is dominated by amino acid derivatives and fatty acids. No chitin-specific compounds were detected in the sheath. These results, contrary to previous reports, show that the polymeric complex of the sheath is composed of proteinaceous moieties, possibly cross-linked to aliphatic components. This study constitutes the first chemical characterization of the pyrolysis products of insect (louse) glue and unequivocally confirms that louse sheaths are not chitinous, as suggested by earlier histochemical studies. Development of agents that might loosen nits from the hair shaft is dependent on research that addresses the chemical composition of the nit sheath.

Amino Acids↗

PubMed2000

Stability of methylecgonidine and ecgonidine in sheep plasma in vitro.

BACKGROUND: Crack smokers are exposed to a pyrolysis product, methylecgonidine (MEG), which can be used as an analytical marker for crack smoking. Ecgonidine (EC), a hydrolytic product of MEG, has been identified in urine of crack smokers. MEG undergoes conversion to EC, complicating analysis and perhaps explaining a lack of forensic blood specimens containing MEG. METHODS: We developed gas chromatography-mass spectrometry (GC-MS) assays for MEG and EC. Plasma was collected from sheep blood containing 0, 0.06, or 0.24 mol/L (0%, 0.25%, or 1%) NaF. MEG was added to these plasmas, and they were incubated at -80, 1, 21, or 37 degrees C to determine whether there were temporal, temperature, or storage effects on MEG stability over 48 h. RESULTS: Decreased temperature and increased NaF concentrations limited MEG degradation and EC formation. MEG stored in plasma at -80 degrees C was stable up to 1 month, even in the absence of NaF. CONCLUSIONS: MEG is stable in sheep plasma collected in commercially available, evacuated blood-collection tubes containing NaF and stored at -80 degrees C. In vitro formation of EC can be minimized with appropriate sample handling, and its in vivo formation may provide a better marker of crack smoking than its parent pyrolysis product.

Animals↗

PubMedDate not supplied

Electrothermal atomization of arsenic, antimony and thallium using a graphite atomizer with refractory metal platforms.

The electrothermal atomization of the volatile elements arsenic, antimony and thallium from a refractory metal platform consisting of a tungsten coil and/or a refractory metal foil with the dimensions of a conventional graphite platform was studied. Several combinations of refractory metal platforms were investigated, as follows: W platform; Ta platform; W coil; W coil on a W platform and W coil on a Ta platform. The best combination for these elements as regards both thermal stabilization and sensitivity is the W coil on a Ta platform. Thermal stabilization is also achieved with a W coil on a W platform. The presence of Pd-containing chemical modifier favors the thermal stabilization of the analytes. The sufficient amount is 2 micrograms of Pd. The maximal temperatures of pyrolysis are higher (arsenic, antimony) or equal (thallium) to those when using different chemical modifiers, added as solutions. It may be concluded, that the refractory metal platforms act as "built-in modifiers". They are suitable for the determination of arsenic, antimony and thallium in samples of complex matrix composition where high thermal stability of the analytes during the pyrolysis step is required.

Air Pollutants↗

PubMedDate not supplied

[Gas chromatographic study of broth cultures of microorganisms as a method of detecting extraterrestrial life].

The method of pyrolysis--gas chromatography was used to study the composition of cultural liquids obtained upon the incubation of desert soil samples in a rich growth medium. The composition of pyrolysis products was found to depend on the time of incubation. Cultural liquids differed in their composition from the original growth medium. This method is a dynamical one, and can be employed to control the activity of microorganisms.

Bacteriological Techniques↗

PubMed2004

[Configuration of pyrolytic chars from waste tires in fluidized bed reactor].

With the fluidized bed as main reactor, the configuration of chars of waste tire was investigated. The change of specific surface area, porosity and specific pore volume of chars received at various temperature, diameter of bed materials and superficial fluidization number was mainly researched. The specific surface area and porosity of chars had the peak value at 650 degrees C or 750 degrees C, which showed there exists the best pyrolysis temperature from the angle of char quality and it will decrease with smaller diameter of bed materials, 0.135-0.304mm. The porosity of chars decreases with the fluidization number increasing. The change tendency of the specific surface area of chars with the fluidization number is correlated with the pyrolysis temperature. At 550 degrees C the specific surface area of chars decreases with the fluidization number increasing, while at 650 degrees C the other way round. The change tendency of the specific pore volume of chars with the temperature is correlated with the diameter of bed materials. With larger bed materials (0.304-0.4mm), the specific pore volume of chars rises at fisrt, then decreases with the temperature increasing, and with smaller bed materials, it decreases with the temperature increasing.

Bioreactors↗

PubMed2004

Intensification of adsorption process by using the pyrolytic char from waste tires to remove chromium (VI) from wastewater.

Pyrolysis has the potential of transforming waste into valuable recyclable products. Pyrolytic char (PC) is one of the most important products from the pyrolysis of used tires. One of the most significant applications for pyrolytic char recovered is used for the removal of Cr(VI) in the wastewater effluent to control waste by waste. The surface chemistry properties of surface element distribution/concentration and chemical structure were examined for the pyrolytic char and the commercial activated carbon (CAC) respectively. The results showed that surfaces of PC possesses a large amount of ester and hydrocarbon graft, whereas there are mainly carbon functional components of C-OH, C=O and COOH on the surface of CAC. Therefore the surface electronegativity of PC is lower than that of CAC in the water. The repulsive interactions between the surfaces of PC and the negatively charged Cr(VI) ion are weaker than that of CAC, which results in an intensification of the adsorption process by the utilization of PC. The adsorption isotherms of Cr(VI) ion on the two kinds of carbons were determined experimentally. The larger adsorption amount on the PC in the case of Cr(VI) may be attributed mainly to its special surface micro-chemical environment. The mechanism of the removal Cr(VI) from aqueous solution was assumed to be the integration of adsorption and redox reaction. The adsorption was the rate-controlled step for Cr(VI) removal. The adsorption of Cr(VI) was identified as pseudo-second-order kinetics. The rate constants of adsorption were evaluated.

Adsorption↗

PubMed1991

A new type of serine-containing glycopeptidolipid from Mycobacterium xenopi.

An unknown immunogenic glycopeptidolipid, named GPL X-1, was isolated from Mycobacterium xenopi, which is a nontuberculous mycobacterium responsible for pulmonary and disseminated infectious diseases mainly occurring in immunocompromised patients. The glycopeptidolipid was purified until homogeneity, in the native form, by direct phase high performance liquid chromatography. A new route is proposed for the structural elucidation of its unusual lipopeptidic core. The presence of allothreonine (aThr), phenylalanine, and serine in the molecular ratio 1:1:2, respectively, was established by reverse phase high performance liquid chromatography analysis of the phenylthiocarbamyl amino acid derivatives. From the molecular mass (1828 Da) of the native glycopeptidolipid, determined by cesium ion liquid secondary ion mass spectrometry using the amphipathic triethylene glycol monobutyl ether matrix, it was deduced that the tetrapeptide was amidified by a dodecanoic acid. The complete structure, C12-Ser-Ser-Phe-aThr-OCH3, of the lipopeptidic core was established by pyrolysis electron impact-mass spectrometry of the native glycopeptidolipid. To date, this is the first example of a mycobacterial glycopeptidolipid with a C12-tetrapeptidic core containing serine. A novel approach, based on two dimensional 1H,1H correlated spectroscopy analysis of the native and peracetylated GPL X-1, was developed, allowing the structural determination of the monosaccharidic residues with their alkali-labile groups "in situ" on the whole complex molecule. 2-O-Acyl-alpha-L-Rhap, alpha-L-Rhap, 2,4-di-O-acyl-6-deoxy-alpha-L-Glcp, 2,3,4-tri-O-Me-alpha-L-Rhap, and 3-O-Me-6-deoxy-alpha-L-Talp were identified, where Me, Rhap, and Talp are methyl, rhamnopyranosyl, and talopyranosyl, respectively. The latter two were localized at the carbohydrate non-reducing ends, and the C-3's of the remaining monosaccharide residues were found involved in the interglycosidic linkage. The alpha anomeric configurations were inferred from the JC-1,H-1 heteronuclear coupling constants, and the L absolute configurations for all the monosaccharide residues were established by gas chromatography analysis of the trimethylsilyl (+/-)-2-butyl glycosides. Finally, by pyrolysis electron impact mass spectrometry of peracetylated GPL X-1, the following tetrasaccharide appendage structure was proposed: 2,3,4-tri-O-Me-L-Rhap(alpha 1----3)-2-O-lauryl-L-Rhap(alpha 1----3)-L-Rhap- (alpha 1----3)-2,4-di-O-(acetyl,lauryl)-6-deoxy-alpha-L-Glcp. Compared to the oligosaccharidic glycopeptidolipid structures, the particular features of the GPL X-1 tetrasaccharide structure arise from the presence of monosaccharide residues esterified by C12 fatty acids and from the absence of the basal disaccharide core, L-Rhap-(alpha 1----2)-6-deoxy-alpha-L-Talp.(ABSTRACT TRUNCATED AT 400 WORDS)

Antigens, Bacterial↗

PubMed1989

The use of soot analysis as an investigative tool in aircraft fires.

Traditionally, carboxyhemoglobin analysis has been used to determine the extent of respiration during a postcrash fire. This is a useful and informative measurement, but advances in the chemical analysis of soot samples provide a new and useful forensic tool for the investigation of deaths by fire. One of the latest analytical techniques is a computer-interfaced pyrolysis mass spectrometry. Soot consists of a high percentage of carbon as well as fragments of the original polymer that are unique to that particular material. Consequently, analysis and identification of the fragment pattern makes it possible to identify the original material from which the soot was generated. In pyrolysis mass spectrometry the soot is pyrolyzed into the ion source and the resulting ion pattern is computer analyzed to identify the polymeric system or systems that generated the soot. Analysis of soot samples collected from the upper respiratory tract of aircraft accident victims and from the accident scene can provide information on the type of toxic insult (identifies specific toxic products), the material(s) that burned and generated the toxic atmosphere, and the relative time of survival following the crash. This technique has been applied to the investigation of fire deaths in a hotel fire and will be used to illustrate the identification of the materials that burned, the toxic products, and the potential for aircraft accident investigations.

Accidents, Aviation↗

PubMed1971

Mass spectrometry of the phosphatidylcholines: fragmentation processes for dioleoyl and stearoyl-oleoyl glycerylphosphorylcholine.

Mass spectra for the various phosphatidylcholines, together with accurate mass measurements on the more abundant fragment ions, have been described in a previous paper (Ref. 5). No detailed fragmentation sequence was proposed on the evidence available. In the case of dioleoyl glycerylphosphorylcholine, some question arose as to whether certain ions were produced by electron impact or by pyrolysis. In this paper, results are reported which enable a more detailed fragmentation sequence to be proposed. By observing metastable transitions in the first field free region of a double-focusing mass spectrometer, it can be shown that the major ions in the spectrum are produced by electron impact processes, and not by pyrolysis; moreover, many of these ions are directly related to one another by metastable processes. In particular, it has been demonstrated that the ions at m/e 603 for dioleoyl glycerylphosphorylcholine and at m/e 604 for stearoyl-oleoyl glycerylphosphorylcholine are derived from the appropriate molecular ions by an electron impact-induced process. From measurements of the metastable ion intensities, as well as from the appearance potentials and ionization efficiency curves, conclusions may be drawn about many of the fragmentation mechanisms, allowing a distinction to be made between rearrangement and cleavage reactions.

Chemical Phenomena↗