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PubMed1993

[Test of a quick differentiation of selected mycobacteria with pyrolytic gaseous chromatography].

The five mycobacterium strains H37Rv series 363, M. bovis (An5) series 250, M. kansasii series 377, M. intracellulare series 364, M. xenopi series 302 and BCG series 180291 were tested using pyrolytic gas chromatography method. After regeneration of lyophylisate, the strains were incubated using L-J medium in 37 degrees C for 2 to 6 weeks--the period that was necessary to obtain profuse growth. The bacterial mass obtained from the culture was collected in test-tubes and pyrolized after autoclave incubation and dry procedure. The CHROM 5 gas chromatograph together with FID detector was used for detecting the products of pyrolysis. The signal was transmitted from the detector to analog-digital converter A/C and registered by IBM PC/XT computer. 12-15 analysis of each strain were performed. Chromatograms of strains pyrolysis products were recorded as files to the hard disc. This way the standard data base was built. The pyrolysis products of tested strains were compared with data base using BAZCHRO program. E. coli JC 7623 was employed as a standard for comparison of chromatograms. The similarity of chromatograms was presented as percentage. The 85-95% of similarity was obtained as a result of comparison of the same Mycobacteria strains.

Chromatography, Gas↗

PubMed1996

Effect of background interference on accelerant detection by canines.

Additional studies were performed with respect to examining the lower limits at which canines can reliably detect products commonly used as accelerants and distinguish them from pyrolysis products or background hydrocarbons. As part of a testing exercise performed in conjunction with a national conference of the Canine Accelerant Detection Association (CADA), 34 canines were subjected to a series of tests, some of them were a recertification proficiency. In one of the tests, the dogs were nearly unanimously successful in locating one can (out of five) containing 50% evaporated gasoline at the 5 microL level on a burnt carpet matrix, and pinpointing the 6-in. square sector on a piece of plain carpeting where the same amount of gasoline (5 microL) was applied. However, only half were able to detect a second doped sample containing a lesser amount (0.05, 0.1, or 0.2 microL) of gasoline, and registered a number of alerts on samples containing only burnt carpeting material. The dogs were also tested on measured amounts (2 or 5 microL) of a variety of other light, medium, and heavy petroleum products applied to a variety of substances containing significant pyrolysis products. As a group, the canines were much less successful in pinpointing these products than they were with gasoline at this same level, and again registered a number of alerts on cans containing only pyrolysis products. The significant number of alerts by canines on samples not containing gasoline or other products points out the importance of obtaining laboratory confirmation on samples on which dogs alert, and on keeping accurate field and training records of canines to establish their credibility.

Animals↗

PubMed1976

[Effect of overheating products of wood hydrolysis on 3,4-benzpyrene output].

Under study was the effect of overheating of wood pyrolysis products at 600 degrees C on the content of 3,4-benzpyrene in them. Overheating only of the water portion of pyrolysis products would increase considerably its BP content, on account of it the total output of the carcinogen is increased. While overheating of total pyrolysis products results in still greater increase of total BP output on account of its concentration rise both in the water portion and resin. Overheating of resin separately would result in a 7 times increase of BP concentration in it.

Benzopyrenes↗

PubMed1997

Isotope ratio mass spectrometric method for the on-line determination of oxygen-18 in organic matter.

A method for the on-line determination of oxygen-18, at a naturally occurring level, in organic material is presented. After pyrolysis of the samples to form carbon monoxide, which is performed at 1300 degrees C in a vitreous carbon tube, the pyrolysis products are transported by a stream of helium gas. Using an open split, a small part of the effluent is transferred to the ion source of an isotope ratio mass spectrometer. The ratio is obtained from a measurement of the ion current intensities at m/z 30 and 28 (12C18O and 12C16O). The method was tested with the secondary water standard GISP (Greenland Ice Sheet Precipitation) and the carbonate standard NBS 19. The values obtained were -24.8/1000 and 27.3/1000 vs. VSMOW (Vienna Standard Mean Ocean Water) (LAEA reference values are -24.8/1000 and 28.7/1000 vs. VSMOW). The potential of the method was demonstrated by measuring the 18O content of samples of beet and cane sucrose and also samples of vanillin extracted from vanilla pods or of synthetic origin.

Acetanilides↗

PubMed1999

Identification of an intact sydnonimine ring depending on the reaction substituents of mesocarb by gas chromatography/mass spectrometry

Trifluoroacylated, trimethylsilylated and methylated mesocarb (3-(1-methyl-2-phenylethyl)-5-[[(phenylamino) carbonyl]amino]-1,2, 3-oxadiazolium) were analyzed by gas chromatography/mass spectrometry (GC/MS). In trifluoroacylation, N-trifluoroacylated sydnophen (SP-NTFA), where the exocyclic nitrogen atom of the sydnonimine ring attacks N-methylbis(trifluoroacetamide), was identified by GC/MS. However, in trimethylsilylation, C-trimethylsilylated sydnophen (SP-CTMS), where the C-4 atom of the sydnonimine ring attacks N-methyl-N-trimethylsilyltrifluoroacetamide, was detected. SP-NTFA and SP-CTMS are intermediates of mesocarb in pyrolysis, and retain an intact sydnonimine ring. In methylation, a ketene form of mesocarb reacts as a nucleophile with methyl iodide to produce methylated N-nitroso-N-cyanomethylamphetamine. Thus, depending on the reaction substituents, the intermediate of mesocarb in pyrolysis was identified to be either an intact sydnonimine ring skeleton or an open-ring compound using GC/MS. Copyright 1999 John Wiley & Sons, Ltd.

Journal Article↗

PubMed1999

Direct analysis of oligomeric tackifying resins in rubber compounds by automatic thermal desorption gas chromatography/mass spectrometry

Two analytical methods, automatic thermal desorption gas chromatography/mass spectrometry (ATD-GC/MS) and pyrolysis gas chromatography/mass spectrometry (Py-GC/MS), were applied as direct methods for the analysis of oligomeric tackifying resins in a vulcanized rubber. The ATD-GC/MS method, based on discontinuous volatile extraction, was found to be an effective means for direct analysis of the oligomeric tackifying resins contained in a vulcanized rubber. The oligomeric tackifying resins, such as t-octylphenolformaldehyde (TOPF) resin, rosin-modified terpene resin, and cashew resin, could be directly analyzed in vulcanized rubber by ATD-GC/MS. Much simpler total ion chromatograms were obtained by ATD-GC/MS than by flash pyrolysis with a Curie-point pyrolyzer, permitting much easier interpretation. Ions at m/z 206, 135, and 107 were fingerprints in the characteristic mass spectra obtained by ATD-GC/MS for TOPF resin in the vulcanized rubber. 1H-Indene, styrene, and isolongifolene were observed as their characteristic mass spectra in the pyrolyzate of the rosin-modified terpene resin. From the cashew resin, phenol, 3-methylphenol, and 4-(1,1,3, 3-tetramethylbutyl)phenol were obtained as the characteristic pyrolyzates by discontinuous thermal extraction via ATD-GC/MS. Copyright 1999 John Wiley & Sons, Ltd.

Journal Article↗

PubMed2000

Syntheses and 1H-, 13C- and 15N-NMR spectra of ethynyl isocyanide, H-C triple bond C-N triple bond C, D-C triple bond C-N triple bond C and prop-1-ynyl isocyanide, H3C-C triple bond C-N triple bond C, D3C-C triple bond C-N triple bond C: high resolution infrared specturm of prop-1-ynyl isocyanide

Ethynyl isocyanide, H-C triple bond C-N triple bond C (1a), deuteroethynyl isocyanide, D-C triple bond C-N triple bond C (1b), prop-1-ynyl isocyanide, H3C-C triple bond C-N triple bond C (1c), and trideuteroprop-1-ynyl isocyanide, D3C-C triple bond C-N triple bond C (1d) are synthesized by flash vacuum pyrolysis of suitable organometallic precursor molecules (CO)5Cr(CN-CCl triple bond CClH) (5a), (CO)5Cr(CN-CCI=CClD) (5b), (CO)5Cr(CN-CCl=CCl-CH3) (5c) and (CO)5Cr(CN-CCI=CCl-CD3) (5d), respectively. Compounds 5a-d are formed in two steps by radical alkylation of tetraethyl-ammonium pentacarbonyl(cyano)chromate, NEt4[Cr(CO)5(CN)] (2) by 1,1,2,2,-tetrachloroethane (3a), 1,1,2,2-tetrachloro-1,2-dideuteroethane (3b), 1,1,2,2,-tetrachloropropane (3c), and 1,1,2,2-tetrachloro- 1,3,3,3-tetradeutero-propane (3d) yielding [(CO)5Cr(CN-CCl2-CCl2-H)] (4a), [(CO)5Cr(CN-CCl2-CCl2D)] (4b), [(CO)5Cr(CN-CCl2-CCl2-CH3)] (4c), and [(CO)5Cr(CN-CCl2-CCl2-CD3)] (4d). Dehalogenation of 4a-d using zinc in diethylether/acetic acid gives 5a-d, respectively. A multinuclear NMR study revealed the 1H-, 13C- and 15N-NMR data of 1a and 1c. Molecular spectroscopic data of 1c were determined by high resolution infrared spectroscopy. The by-products of the pyrolysis are the E and Z isomers of the halogenated ethenyl isocyanides H(Cl)C=CCl-NC (6a) and H3C(Cl)C=CCl-NC (6c) which have been characterized by IR, MS and NMR spectroscopy.

Journal Article↗

PubMed1989

Electron impact mass spectrometry of BHT and its alteration products.

The electron impact (EI) mass spectra of 2,6-di-tert-butyl-4-methylphenol (BHT) and certain of its alteration products are described in detail. Accurate mass measurements confirm the elemental compositions of important fragment ions in the EI spectra. Collisionally activated mass spectra are also used to study fragmentation and suggest common ion structures. The reference spectra provide the basis for identifying various alteration products of BHT by capillary gas chromatography/mass spectrometry (GC/MS) without the necessity of isolating individual components. Application of GC/MS is made to three studies: (i) pyrolysis of hydroperoxy-BHT as a potential pathway to alteration products in food; (ii) GC/MS pyrolysis of hydroperoxy-BHT as a model study; and (iii) alteration of BHT in ethanol/water as a food-simulating solvent.

Butylated Hydroxytoluene↗

PubMedDate not supplied

Airway reactivity response to aged carbon-graphite/epoxy composite material smoke.

Exposure of naïve guinea pigs for a total of 30 min to aged smoke from pyrolysis of 5, 10 and 100 g of carbon-graphite/epoxy-advanced composite material (cgeCM) elicited changes in the ventilation and breathing pattern reminiscent of an acute, asthmatic episode. The severity of these responses was dose related. Although breathing pattern changes were not definitive of stimulation by a single type of respiratory irritant, non-dimensional indices derived from breath structure appeared to be characteristic of bronchoconstriction possibly complicated by CO(2)-stimulated ventilation. The highest exposure concentration also elicited convulsions in the animals, which may or may not be related to the airway reactivity (AR) response. Upon treatment with fresh air, breathing returned to normal. However, this recovery was transient with some respiratory parameters returning to abnormal levels, possibly indicating a rebound or delayed component of the response. Filtration of particulate material from the smoke moderated but did not eliminate the AR response. Animals exposed to diluted smoke from the pyrolysis of 2 g of cgeCM showed no remarkable changes in breathing or ventilation, suggesting that there may be a threshold for aged cgeCM smoke-elicited AR response.

Animals↗

PubMed1986

Retrieval and analysis of a clinical total artificial heart.

Examination by light microscopy, scanning electron microscopy (SEM), and x-ray microanalysis of a clinical total artificial heart (TAH) implanted for 112 days revealed no evidence of calcification, pannus, or vegetative thrombus. A macroscopic thrombus was seen along the suture line in the right atrium but did not obstruct blood flow or valve function. Microscopic thrombi (less than 0.1 mm) and evidence of microemboli were observed on the pumping diaphragm using SEM. Characterization of selected polyetherurethane (PEU) samples from the pumping bladders and housing by Curie-point pyrolysis mass spectrometry (Py-MS) revealed unexpected differences between postmortem retrieved ventricles. Although the origin of these differences could be traced back to batch-to-batch variations in the original PEU material (Biomer), the precise nature of the observed differences in chemical structure and/or composition is still unknown. Numerical comparison between pyrolysis mass spectra from PEU samples exposed to blood or tissue and unexposed samples from the same ventricles did not detect evidence of biodegradation. Continual improvements in fabrication and quality control should minimize surface imperfections and ensure polymer reproducibility; however, existing materials and design parameters appear to be adequate for continued clinical implantation.

Electron Probe Microanalysis↗

PubMed1995

Pyrolysis/gas chromatography/mass spectrometry of lignocellulose.

The use of pyrolysis/gas chromatography/mass spectrometry (PY/GC/MS) to determine the molecular composition of lignocellulose is reviewed and the technique illustrated with applications on some novel systems. Constituents and structural arrangement of lignocellulosic polymers in plant cell wall are briefly described. The basic principles of pyrolysis and the main advantages and disadvantages of PY/GC/MS are discussed. PY/GC/MS analyses of (a) paper industry effluents, (b) agricultural by-products subjected to biological processes of delignification and (c) recycled paper are presented as examples of the amount of information that PY/GC/MS can provide on lignin classification and monitoring of delignification treatments as well as on the fingerprinting of lignocellulosic materials. The ion trap detector mass spectra of 56 pyrolysis products of lignocellulose, including compounds of phenolic, furanic and pyranic nature, are shown.

Cellulose↗

PubMed2004

A new method for determining delta13C and deltaD simultaneously for CH4 by gas chromatography/continuous-flow isotope-ratio mass spectrometry.

A continuous-flow technique has been developed to analyse the deltaD and delta(13)C values for CH(4) from gas samples, in a single run. This is achieved by splitting the sample gas stream and directing the streams simultaneously through a CuNiPt combustion reactor and an alumina pyrolysis reactor. The CO(2) from CH(4) combustion is trapped in a liquid nitrogen trap while the H(2) exiting the pyrolysis reactor is directed to the mass spectrometer for deltaD(CH4) determination. The CO(2) is then sublimed and directed to the mass spectrometer for delta(13)C(CH4) determination. Sample runs take approximately 10 minutes. This technique gives accurate delta(13)C(CH4) results to within +/-0.3-0.5 per thousand and deltaD(CH4) results to within +/-2-5 per thousand. Injection volumes between 0.5 and 2.5 microL of CH(4), equivalent to between 20 and 100 nmol CH(4), are required for accurate delta(13)C and deltaD analyses, respectively, using sample injection into a split flow with a split ratio of 10. This method provides rapid, accurate and reproducible results on multiple sample runs and is, therefore, an ideal method for analysing natural gas samples from a variety of sources.

Journal Article↗

PubMed2004

Stable oxygen isotopes from theropod dinosaur tooth enamel: interlaboratory comparison of results and analytical interference by reference standards.

Although previous work has demonstrated that biological phosphates ('biophosphates') record significant changes in delta18O associated with variations in local climate and seasonality, the repeatability of these analyses between laboratories has not previously been tested. We serially sampled enamel on four Cretaceous dinosaur teeth for phosphate delta18O analysis at up to three different facilities. With the exception of one set of unprocessed enamel samples, the material supplied to each laboratory was chemically processed to silver phosphate. Each laboratory analyzed sample sets by pyrolysis (thermochemical decomposition) in a ThermoFinnigan TC/EA attached to a ThermoFinnigan Delta Plus mass spectrometer. Significant interference between phosphate samples and the NIST reference material 8557 barium sulfate (NBS 127) distorts some of the results. Samples analyzed immediately following NBS 127 may be depleted by 6 per thousand isotopically and in instrument peak amplitude response by 80%. Substantial interference can persist over the subsequent 20 silver phosphate samples, and can influence the instrument peak amplitude response from some organic standards. Experiments using reagent-grade silver phosphate link these effects to divalent cations, particularly Ca2+ and Ba2+, which linger in the reactor and scavenge oxygen evolved from pyrolysis of subsequent samples. Unprocessed enamel includes 40 wt% calcium and self-scavenges oxygen, disrupting the isotopic measurements for the first half of a set and depleting subsequent organic standards by up to 9 per thousand. In sets without NBS 127 or calcium, such interference did not occur and an interlaboratory comparison of results from enamel shows reproducible, significantly correlated peaked delta18O patterns with a 2-3 per thousand dynamic range, consistent with previous results from contemporaneous teeth. Whereas both unprocessed enamel and the NBS 127 barium sulfate should be applied to biological phosphate ('biophosphate') stable isotope research with caution, seasonal variations in enamel phosphate delta18O are a paleoecologically valuable, reproducible phenomenon in theropod dinosaur teeth.

Animals↗

PubMed2002

Measurements by gas chromatography/pyrolysis/mass spectrometry: fundamental conditions in (2)H/(1)H isotope ratio analysis.

Gas chromatography/pyrolysis/isotope ratio mass spectrometry (GC/P/IRMS) is a relatively new method for on-line determination of (2)H/(1)H isotope ratios. The influence of different parameters on the (2)H/(1)H isotope ratios obtained in GC/P/IRMS has been thoroughly studied using several flavor compounds, such as 5-nonanone, linalool, menthol, linalyl acetate and 4-decanolide. The requirement of "conditioning" the pyrolysis reactor to obtain reliable delta(2)H(V-SMOW) values is discussed. Furthermore, the influence of the carrier gas flow of the gas chromatograph on the completeness of pyrolysis and subsequently on the delta(2)H(V-SMOW) values is investigated in detail. The linear range of the compounds investigated is determined. The results show that calibrating the GC/P/IRMS system with secondary standard substances is absolutely necessary in order to obtain reliable delta(2)H(V-SMOW) values. In view of interlaboratory comparability, validation procedures are recommended.

Journal Article↗

PubMed2002

On-line measurement of intramolecular carbon isotope distribution of acetic acid by continuous-flow isotope ratio mass spectrometry.

Molecular and intramolecular carbon isotope measurements of acetic acid present in natural environments have been performed by off-line procedures. The off-line method is complicated and time-consuming and requires micromolar to millimolar amounts of sample. This limits geochemical isotopic studies, especially at the intramolecular level, on acetic acid present in natural samples. Here, we examine an on-line measurement of intramolecular carbon isotope distribution of acetic acid using continuous-flow isotope ratio mass spectrometry (CF-IRMS) coupled with an on-line pyrolysis system. This is achieved by measurement of the respective carbon isotope ratios of CH4 and CO2 produced by on-line pyrolysis of acetic acid. Results for authentic standards of pure acetic acid demonstrated the practicality of this on-line method, although the carbon isotope ratio of the methyl group could not be determined directly. The precision of the carbon isotope measurements was 0.4 per thousand (1sigma). The carbon isotope distribution determined by the on-line method was identical to that determined by the conventional off-line method within analytical error. The advantages of the on-line method compared with the conventional off-line method are that it is less laborious, requires less analytical time (less than one hour per sample) and, most importantly, uses smaller sample sizes (ca. 10 nanomole). An application of this on-line method to natural geochemical samples will provide an insight into the geochemical cycle of acetic acid.

Acetic Acid↗

PubMed2000

Surface Properties of Mesoporous Carbon-Silica Gel Adsorbents.

Carbon/silica (carbosil) samples prepared utilizing mesoporous silica gel (Si-60) modified by methylene chloride pyrolysis were studied by nitrogen adsorption, quasi-isothermal thermogravimetry, p-nitrophenol adsorption from aqueous solution, and (1)H NMR methods. The structural characteristics and other properties of carbosils depend markedly on the synthetic conditions and the amount of carbon deposited. The changes in the pore size distribution with increasing carbon concentration suggest grafting of carbon mainly in pores, leading to diminution of the mesopore radii. However, heating pure silica gel at the pyrolysis temperature of 550 degrees C leads to an increase in the pore radii. The quasi-isothermal thermogravimetry and (1)H NMR spectroscopy methods used to investigate the water layers on carbosils showed a significant capability of carbosils to adsorb water despite a relatively large content of the hydrophobic carbon deposit, which represents a nonuniform layer incompletely covering the oxide surface. Copyright 2000 Academic Press.

Journal Article↗

PubMed1999

Generation, Microwave Spectrum, and Ab Initio MO Calculation of trans-1-Nitrosopropene, CH3CH&dbond;CH-NO (syn form).

trans-1-Nitrosopropene (syn form) was generated in the gas phase by pyrolysis of 1-chloro-1-methyl-2-(hydroxyimino)ethane and identified by microwave spectroscopy. The microwave spectrum of the pyrolysate was observed in the frequency range from 8.0 to 40.0 GHz. The rotational constants (MHz) were determined as A = 34 025(390), B = 2315.62(2), and C = 2198.54(2) for CH3CH&dbond;CH-NO (normal species) and A = 34 012(530), B = 2300.04(3), and C = 2182.70(2) for CH3CH&dbond;CH-15NO (15N isotopic species) in the ground vibrational state. The values of planar moment (Pcc = (Ia + Ib - Ic)/2) obtained for the normal and 15N isotopic species were found to be 1.62(10) and 1.52(13) uÅ2, respectively. These values are almost the same within the limit of errors. This suggests that the nitrogen atom lies in or is close to the ab inertial plane of the molecule and shows also that only two hydrogen atoms are located symmetrically out of the symmetry plane. The pyrolysate was determined to be trans-1-nitrosopropene by comparing the observed and calculated rotational constants, kappa (Ray's asymmetric parameter), and rs coordinates of the nitrogen atom. One vibrationally excited state was observed and assigned to the C-N torsional mode (158(50) cm-1). Interesting pyrolysates such as hydrogen cyanide and acetaldehyde were also detected during the pyrolysis of the precursor. The lifetime of trans-1-nitrosopropene is found to be ca. 5 s in the waveguide cell. Copyright 1999 Academic Press.

Journal Article↗

PubMed2005

Mechanisms of acrylamide formation: Maillard-induced transformation of asparagine.

The formation of acrylamide (AA) from L-asparagine was studied in Maillard model systems under pyrolysis conditions. While the early Maillard intermediate N-glucosylasparagine generated approximately 2.4 mmol/mol AA, the Amadori compound was a less efficient precursor (0.1 mmol/mol). Reaction with alpha-dicarbonyls resulted in relatively low AA amounts (0.2-0.5 mmol/mol), suggesting that the Strecker aldehyde pathway is of limited relevance. Similarly, the Strecker alcohol 3-hydroxypropanamide generated low amounts of AA (0.2 mmol/mol). On the other hand, hydroxyacetone afforded more than 4 mmol/mol AA, indicating that alpha-hydroxycarbonyls are more efficient than alpha-dicarbonyls in transforming asparagine into AA. The experimental results are consistent with the reaction mechanism proposed, i.e. (i) Strecker-type degradation of the Schiff base leading to azomethine ylides, followed by (ii) beta-elimination of the decarboxylated Amadori compound to release AA. The functional group in beta-position on both sides of the nitrogen atom is crucial. Rearrangement of the azomethine ylide to the decarboxylated Amadori compound is the key step, which is favored if the carbonyl moiety contains a hydroxyl group in beta-position to the N-atom. The beta-elimination step in the amino acid moiety was demonstrated by reacting under pyrolysis conditions decarboxylated model Amadori compounds obtained by synthesis.

Acetone↗