Pyrolysis Gas-liquid Chromatography Research Articles

Characterisation of a unique ‘asphalt’ sample from the early 19th century Hafkenscheid painting materials collection by analytical pyrolysis MS and GC/MS

Asphalt has been used since antiquity for various purposes and by painters since the 17th century. Asphalt as a pigment material with a known pre-19th century provenance is extremely rare. The analytical pyrolysis techniques of direct temperature-resolved mass spectrometry (DTMS) and pyrolysis gas liquid chromatography coupled with mass spectrometry (Py-GC/MS) were applied to characterise a unique ‘asphalt’ sample from a painting materials collection dating from the early 19th century. The provenance of this sample was investigated by comparison with a sample from a present day floating asphalt from the Dead Sea. DTMS demonstrated a complex envelope of ions from hydrocarbons ranging past m/z 1000 in both samples. Both samples showed evaporating sets of compounds as well as pyrolysing materials evolving from asphaltenes. Asphaltene network polymers were marked by aliphatic cross-links releasing alkenes and alkanes, and aromatic centres releasing alkylbenzenes, alkylnaphthalenes, alkylanthracenes, alkylphenanthrenes, and alkylbenzothiophenes. Hopanoid hydrocarbons and C-ring monoaromatic steroid hydrocarbons were among the biomarker compounds identified. Particularly striking were homologous series of alkylbenzothiophenes and alkyldibenzothiophenes with long hydrocarbon chains that could be traced with DTMS and confirmed by DTMS/MS. The results indicate that the early 19th century ‘asphalt’ sample from the Hafkenscheid collection is indeed a true asphalt that shows many similarities to the Dead Sea asphalt sample, which is therefore proposed as the possible region of provenance.

Pyrolysis–gas–liquid chromatography with atomic emission detection for the identification of Corynebacterium species

We report here the application of pyrolysis–gas chromatography followed by atomic emission detection (AED) for the characterisation of microorganisms. AED measured the quantity of carbon, sulfur and nitrogen in the molecules separated chromatographically. Twenty-three strains, representing eight Corynebacterium species, were tested in this preliminary study. Co-ordinate principal analysis grouped 11 strains in their respective species group. Most of the other strains appear randomly distributed, perhaps because these strains require additional nutrients. These preliminary results show that the method could be used as a tool for the taxonomic and perhaps the epidemiologic characterisation of bacteria.

The Value of Pyrolysis-Gas-Liquid Chromatography in the Taxonomy of Some Ascogenous Yeasts

Summary Pyrolysis-gas liquid chromatography analysis were carried out on 28 strains of yeasts belonging to the Ascomycetes. A large number of quantitative and qualitative differences were observed in the different pyrograms. These results were compared and the similarities calculated by computer analysis. With pyrolysis, different yeasts could be classified into groups which correspond with the present classification system. The 28 strains studied could be separated within 49 h, in comparison with the 7–10 days with conventional methods.

Pyrolysis gas—liquid chromatography of N,N-dimethyl-alkylamine N-oxides and their mixtures

A rapid quantitative and small scale method based on direct injection pyrolysis gas—liquid chromatography is described for the determination of N,N-dimethylalkylamine N-oxides. The method is suitable for determination of individual N-oxides as well as of their homologous compositions with or without the presence of parent tertiary amines in water or methanol solutions. The sensitivity of the method is 10–15 nmol of compounds injected. The unsymmetrical (1-methyldodecyl)dimethylamine N-oxide forms two isomeric alkenes 1-tridecene and trans-2-tridecene in a ratio of 1.68, in agreement with the predicted value.

Pyrolysis‐GLC applied to composition analysis, general characterisation and the detailed specification of polymers

AbstractSince its inception in the late 1950s, pyrolysis gas‐liquid chromatography has rapidly become an important tool for the polymer chemist. Applications range from polymer characterisation to the elucidation of polymer degradation mechanism. Typical analytical applications include the characterisation of complex polymer mixtures, the assessment of copolymer composition and microstructure, structural analysis and the assignment of polymer tacticity. Recent advances in the technique are reviewed and examples of results are given.Most current GLC equipment is perfectly adequate for polymer/copolymer analysis provided that certain basic requirements are satisfied. For polymer characterisation, furnace and Curie‐Point methods are not the most appropriate and even simple filament methods are preferable to these. Refined filament techniques are the most suitable methods for studying degradation kinetics, and can provide a highly precise specification of polymer structure.For example, studies on the dependence of the specific rate of pyrolysis can distinguish anionic and free‐radical polymers. Analysis of the energetics of the degradation may indicate the activation energy for end initiation; this may be compared with bond‐strengths of possible end‐group structures. A similar process can be used to elucidate the nature of possible ‘weak‐links’ within the polymer backbone. The effects of polymer modification, for example oxidation, may also be assessed. Examples are quoted for these situations and the requirements of the technique are stressed.

The staphylococci: A classification and identification study using pyrolysis-gas-liquid chromatography

Packed-column Curie-point pyrolysis-gas-liquid chromatography (Py-GC) was used to produce a characterisation database of 200 pyrograms representing 10 species of staphylococci. Discriminant analysis showed Staphylococcus xylosus was very poorly distinguished from S. saprophyticus. S. warneri proved heterogeneous in both Py-GC and conventional biochemical tests. These species were discarded from the database. S. epidermidis gave two pyrotypes, with 10% of strains in pyrotype 2; 20 pyrograms representing pyrotype 2 were added to the database. 451 strains, mostly clinical, were identified in Py-GC and in three independent biochemical schemes. Py-GC results were compared with the consensus of these three schemes. Some (19) failed to give a consensus, a further 12 identified biochemically as S. warneri and 5 as S. xylosus. Of the remaining 415 strains, only 60 showed disagreement between Py-GC and biochemical identification. Eighteen S. epidermidis strains identified as S. haemolyticus or S. capitis in Py-GC; 14 gave characteristic pyrograms similar to S. epidermidis pyrotype 2 in Py-GC and represent intermediates between typical and pyrotype 2 strains. Many (20) of the remaining mis-identified strains were atypical in biochemistry and may represent undescribed species, mis-identifications in consensus or extreme species variants. The individual biochemical identification schemes showed agreement rates (79–85%) comparable to Py-GC when matched with the consensus of the other methods. Py-GC classification differentiated the species S. aureus, S. cohni, S. capitis, S. hominis, S. haemolyticus, S. epidermidis, S. epidermidis prototype 2 and S. simulans. S. xylosus and S. saprophyticus formed a single cluster. S. warneri strains did not cluster well, but a minority formed a linking group between S. epidermidis and S. capitis.

The thermal degradation of poly(acenaphthylene)

The thermal stability of poly(acenaphthylene) has been studied by pyrolysis gas-liquid chromatography and pyrolysis mass spectrometry. The principal degradation product is acenaphthylene monomer, with smaller amounts of a similar compound, possibly the saturated acenaphthene. Small yields of a dimeric oligomer were also observed. Mechanisms for product formation are suggested.

Characterization of biopolymers by pyrolysis gas chromatography and multidimensional analysis : Application to synthetic melanins

A method for characterization of the melanin biopolymer has been developed and validated by the use of synthetic melanins derived from tyrosine, dopamine or hydroquinone. The technique involved pyrolysis gas-liquid chromatography with capillary columns. A back-flushing technique is described which improves pyrogram reproducibility such that closely related melanins can be distinguished with the aid of principal components analysis and non-metric multidimensional scaling.

Pyrolysis gas-liquid chromatography of the pathotypes of the potato cyst nematodesGlobodera rostochiensisandG. pallida

SUMMARYCurie-point pyrolysis gas-liquid chromatography (PGLC) was used to detect gross chemical differences between the 8 European pathotypes of the potato cyst nematodesGlobodera rostochiensisandG. pallida. No qualitative differences were seen with either flame ionization or flame photometric detection systems, although quantitative differences between pathotypes were detected. Cluster analysis of these differences failed to group the pathotypes into species, but separation of some economically important pathotypes was achieved. The potential of PGLC for nematode identification is discussed.

Identification of staphylococci by pyrolysis gas-liquid chromatography.

The identification of bacteria by pyrolysis gas-liquid chromatography (PGLC) was evaluated with the genus Staphylococcus. A matrix containing the characteristics of seven species of Staphylococcus was constructed from the results obtained with 42 named strains identified by biochemical methods. An identification program based upon this database was evaluated in tests with 100 isolates of catalase-positive oxidase-negative gram-positive cocci identified by biochemical and PGLC systems. Agreement between the two systems was 90%. Pure cultures of unknown isolates were identified within 30 min by PGLC using a microcomputer data acquisition and analysis program. A taxonomic analysis of the data is presented, and methods for quality control of PGLC, prolongation of column life, and data analysis are described and discussed.

Rapid diagnosis of systemic candidiasis in children with cancer by pyrolysis gas liquid chromatography.

A pyrolysis gas liquid chromatographic method for detection of Candida antigen in patients with disseminated candidiasis is described. The test was positive in 73% of cases and no false positives or false negatives were noted in controls.

The Inability of Pyrolysis Gas-Liquid Chromatography to Differentiate Selected Foodborne Bacteria

Pyrolysis gas-liquid chromatography (PGLC) and stepwise discriminant analysis (SDA) were ineffective when used to differentiate selected genera, species and strains of foodborne microorganisms. Each of 18 individual bacterial strains analyzed was grown, harvested and subjected to PGLC analysis. The resulting pyrolysis products were separated on a high resolution capillary column and the elution patterns (pyrograms) were subjected to stepwise discriminant analysis of 26 (a–z) characteristic peaks. Classification with the combination of PGLC and SDA was 87% accurate for gram-negative strains of bacteria and 94% accurate for gram-positive strains of bacteria. PGLC-stepwise discriminant· analysis correctly discriminated 80% of the bacterial strains according to the known gram-stain reactions. Only 63% were correctly classified to the genus level when all samples were compared. These findings point out the weak points for this method of bacterial analysis.

Differentiation of Streptococcus mutans serotypes by discriminant analysis of pyrolysis—gas—liquid chromatography data

Curie-point pyrolysis with a relatively low resolution gas—liquid chromatographic system (packed Carbowax 20M columns) provided data on washed cells of oral streptococci. When the data were ordered into a hierarchy of comparisons the steps were matched not only by the increase in variability between sets but also by the proportion of the output showing relatively high variability. It was possible to segregate strains of Streptococcus mutans serotype c from those of different serotypes by use of a discriminant function derived from only three pyrogram peaks.

Rapid Radiometric Method for Detection of Salmonella in Foods

[This corrects the article on p. 648 in vol. 40.].

Virulence Prediction of Yersinia enterocolitica by Pyrolysis Gas-Liquid Chromatography

Virulence Prediction of <i>Yersinia enterocolitica</i> by Pyrolysis Gas-Liquid Chromatography

Virulence prediction of Yersinia enterocolitica by pyrolysis gas-liquid chromatography.

Pyrolysis gas-liquid chromatography (PGLC) was used to differentiate between HeLa cell-invasive and noninvasive strains of Yersinia enterocolitica and between Sereny-positive and -negative strains. A temperature-programmed gas-liquid chromatograph, equipped with a high-resolution Carbowax 20M coated capillary column, separated the volatiles from pyrolyzed whole cells preparations and cell wall fractions. The resulting pyrolysis elution patterns (pyrograms) were divided into 313 30-s time interval areas. The time interval areas were normalized in relation to the entire pyrogram area and were evaluated by stepwise linear discriminant analysis. The results of the PGLC-statistical analyses showed good correlation in prediction of the HeLa cell invasivity test. The technique of PGLC coupled with statistical analyses is objective, in contrast to traditional methods of determining pathogenicity of Y. enterocolitica.

Effect of different growth conditions on the discrimination of three bacteria by pyrolysis gas-liquid chromatography.

High-resolution pyrolysis gas-liquid chromatography was applied to three bacteria (Escherichia coli NCTC 9001, Pseudomonas putida (NCIB 9494, and Staphylococcus aureus NCTC 8532) grown under a variety of conditions. Changing the culture medium drastically altered the quantitative aspects of the pyrograms of all three organisms, but the effects of culture time and incubation temperature were less severe. Mathematical analysis of the relative peak heights showed that four peaks could be used to discriminate the three bacteria however they were cultured.

An Investigation of the Relationship between Bacillus cereus, Bacillus thuringiensis and Bacillus mycoides using Pyrolysis Gas-Liquid Chromatography

Nine strains of Bacillus mycoides, 10 of Bacillus cereus and 18 of Bacillus thuringiensis were analysed using pyrolysis gasliquid chromatography. Application of canonical variates analysis to the resultant pyrograms showed that these organisms formed three distinct groups. Stepwise discriminant analysis with jacknifing showed that of the original 27 peak heights used to define the canonical variates axes, only two were needed to obtain reasonably stable discriminant functions. These discriminant functions ( Dixon, 1975 ) are potentially valuable in identification. Jacknifing also indicated that, had it been an unknown, one strain of B. mycoides would have been incorrectly identified as B. cereus.

Characterization of Bacillus subtilis, Bacillus pumilus, Bacillus licheniformis, and Bacillus amyloliquefaciens by Pyrolysis Gas-Liquid Chromatography, Deoxyribonucleic Acid-Deoxyribonucleic Acid Hybridization, Biochemical Tests, and API Systems

Eight strains each of Bacillus subtilis, Bacillus pumilus, Bacillus licheniformis, and Bacillus amyloliquefaciens were analyzed by using pyrolysis gas-liquid chromatography. Statistical analysis with canonical variates gave four well-separated groups, which represented the four species. Further analysis of the same strains by deoxyribonucleic acid-deoxyribonucleic acid hybridization and API identification systems confirmed the discrimination obtained with pyrolysis gasliquid chromatography. However, analysis by biochemical tests performed in the classical way gave only three groups since it was not possible to achieve separation of the strains representing B. subtilis from those of B. amyloliquefaciens when these tests were used.

Use of principal components analysis for displaying variation between pyrograms of micro-organisms

Principal components analysis is used to display variations between batches of pyrograms of micro-organisms represented by sets of peak heights. Although it is not usually suitable for discriminating genus or species groups, it provides a means of detecting aberrant analyses, unsuspected trends in the data and of assessing reproducibility. It can also provide information relating specific peaks or sets of peaks to clusters of samples. These uses of principal components analysis are not confined to pyrolysis—gas—liquid chromatography; the technique can be applied widely to quantitative chromatographic and mass spectrometric data.