裂解色谱法甲基化试剂碱性对多不饱和脂肪酸降解和异构化的影响

采用最佳比例裂解甲基化试剂,消除了强碱性甲基化试剂对油脂中多不饱和脂肪酸降解和异构化作用的影响。考察了不同比例甲基化试剂的碱性对多不饱和脂肪酸降解和异构化的程度。     

Instrumentation for curie-point pyrolysis/gas chromatography using high-resolution glass open-tubular columns

Summary A Curie-point pyrolyzer using ferromagnetic tubes as sample supports has been designed to be coupled to glass open-tubular columns. For optimum operation of the pyrolyzer as well as of the separation system, independent carrier gas flow-rates may be selected. All potential contaminants diffusing from structural parts are purged without coming into contact with the sample. With full maintenance of the currently available resolving power, pyrolysis gas chromatograps free of extraneous signals are obtained for sample sizes greater than 10 ng.     

Hyphenation of Curie-point-pyrolysis high-resolution gas chromatography with several spectroscopic methods for the analysis of cured epoxy resins

The coupling of Curie-point pyrolysis (Py) with gas chromatography (GC) and mass spectrometry (MS) or Fourier transform infrared spectroscopy (FTIR) has been widely reported. The approach reported in this paper combines chromatographic separation with eluent monitoring by use of three different spectroscopic detectors (MS, FTIR and Atomic Emission Detector [AED]). The features of these detectors, with different selectivities, are shown for the analysis of cured epoxy resins. Besides characterisation of major resin constituents by identification of the pyrolysis products, the usefulness of the AED is also revealed by the detection of minor compounds (such as coupling agents) in cured epoxy resins.     

Determination of the carbon isotopic composition of whole/intact biological specimens using at-line direct thermal desorption to effect thermally assisted hydrolysis/methylation

In this paper, we discuss the use of a direct thermal desorption (DTD) interface as an alternative to Curie-point flash pyrolysis system as an inlet technique in gas chromatography-combustion isotope-ratio mass spectrometry (GC/C-IRMS) analysis of whole/intact phytoplankton and zooplankton specimens. The DTD in combination with a combipal auto-injector is programmed to perform the injection, evaporation of solvents, transport of capped programmed-temperature vaporizer (PTV) liners to the PTV injector and chemical derivatisation (thermally assisted hydrolysis/methylation; THM) such that a profile of a cellular fatty acids is obtained. Flow-cytometric sorted microalgae and handpicked zooplankton are used as samples with trimethylsulfonium hydroxide (TMSH) as methylating reagent. A major advantage of this novel approach over the Curie-point technique is the automation of the total procedure, which allows unattended analysis of large sample series. The profiles and delta(13)C carbon isotopic signatures of the fatty acid methyl esters (FAMEs) produced are very similar to those obtained using the Curie-point flash pyrolysis method. It is shown that algal samples must be kept no longer than 48 h in the DTD sample tray prior to the THM-analysis in order to maintain the integrity of their FAME profile.     

Investigations of model systems of the Maillard reaction: II. Pyrolysis—gas chromatography—mass spectrometry analysis of some non-volatile products of the reaction of d-glucose and 4-chloroaniline

Low molecular weight compounds resulting from the reaction of d-glucose with 4-chloroaniline were subjected to Curie-point pyrolysis, and the cleavage products were identified by gas chromatography—mass spectrometry. Based on their structures, some general features were detected which possibly are applicable to the structural analysis of higher molecular weight Maillard compounds of this type. It is shown in one example that pyrolysis and electron impact mass spectrometry obviously prefer similar fragmentation patterns. In addition to Curie-point pyrolysis, Pyrotest pyrolysis and dry distillation were also tested but yielded less reproducible results.     

Determination of the antioxidant alurofen in synthetic rubbers by pyrolysis-gas chromatography

A pyrolysis—gas chromatographic (Py—GC) method for the determination of the antioxidant Alurofen in synthetic rubbers was developed. The Alurofen was extracted from the rubber, then pyrolysed as 873 K in continuous-mode furnace pyrolyser in 20 s. Chromatographic conditions for the separation of the pyrolysis products were established. The pyrolysis of the Alurofen at several temperatures was investigated by measuring the yields of the pyrolysis products. It was observed that 2-phenyl-2-(4-hydroxyphenyl)propane was produced in the greatest, amounts, and the effect of the pyrolysis temperature on the yield of this compound was studied. The overall Py—GC method for the determination of the Alurofen content of rubbers had a mean relative error of 2.7% and a relative standard deviation of 2.94%.     

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.     

A comparison of various pyrolysis experiments for the analysis of reference humic substances

The interpretation of the results of pyrolysis studies of humic substances is fraught with difficulties if only a single analytical technique is employed for substructure analyses. In this paper we have carried out investigations into humic substances utilising the additional information from the combination of gas chromatography/infrared spectroscopy and gas chromatography/mass spectrometry detection following Curie-point pyrolysis at five different temperatures. The results were compared to those obtained from conventional flash pyrolysis. The aim was to ensure the validation of the results of the compounds identified by at least one other spectroscopic technique. Some 30 substances have been positively identified by infrared spectroscopy, although their appearance is dependent on pyrolysis method and temperature. Most assignments were validated by mass spectrometry or the substance class confirmed.     

Pyrolysis—gas chromatography of methyl methacrylate—styrene and methyl methacrylate—α-methylstyrene copolymers

The pyrolysis—gas chromatographic behaviour of methyl methacrylate copolymers with styrene or α-methylstyrene was investigated with a Curie-point pyrolyzer. Monomer yield from each copolymer was very high as a result of the high probability of unzipping. Though only small quantities of dimers and or trimers are formed on the pyrolysis of two copolymers, they reflect the sequence distribution of copolymers. Under some assumption, the run number of each copolymer is calculated using the amounts of dimer and or trimer formed.     

Multichannel autosampler for Curie-point pyrolysis capillary gas chromatography

A multichannel autosampler which can automatically analyze up to 20 samples in sequence has been developed for on-line Curie-point pyrolysis – capillary GC. The results obtained from the system show that the analysis of thermally labile samples could be performed without either thermal degradation or reaction during the waiting time before the final pyrolysis. The reproducibilities of the relative peak areas and retention times of the characteristic pyrolysates of a tricomponent copolymer were significantly better than those obtained by manual sample manipulation.     

Determination of sodium dodecylbenzene sulfonate in ternary mixtures by curie-point pyrolysis gas chromatography coupled to multivariate analysis

Summary Multivariate analysis was used to develop a viable method for determination of sodium dodecylbenzene sulfonate (DBS) by Curie-point pyrolysis gas chromatography. The pyrograms obtained were normalized against a maximum peak area and peak height. Normalized values were used for Quantification IV, which is one of the multivariate analysis methods, to select useful values initially. Then cluster analysis was carried out using both the selected values and their deviations. This method corresponds to qualitative analysis and indicates which data-base is similar to the sample. On the basis of this data-base, calibration data-bases are chosen. Principal component analysis (PCA) was performed using the calibration data-base and a set of sample data simultaneously. The principal component scores and contribution coefficients obtained were used to construct a calibration curve from which the DBS content of the sample was calculated. The results are in fair agreement with theoretical values.     

Pyrolysis—gas chromatography of networks

Cis-1,4-polybutadiene was exposed to different doses of β-radiation (5–100 Mrad), and polybutadiene samples with different contents of 1,2- and 1,4-isomers were exposed to equal doses of radiation (50 Mrad). The cross-linked products were characterized by sol—gel analysis, distribution of the molar masses of the sol fraction, determination of the degree of swelling and compressibility, and pyrolysed by means of a Curie-point pyrolyser at 770°C in 4 s. Evaluation of the pyrograms taken with the help of a capillary gas chromatograph proved that pyrolysis—gas chromatography enables statements regarding the micro-structure of these cross-linked polymers to be made through the degradation products 1-cis-2- and 1-trans-2-dimethylcyclopropane, 2-methyl-1,3-butadiene and trans-1,3-pentadiene in a very short time without much preparation of the samples. The peak areas of 1,3-butadiene and 4-vinylcyclohexane can be used to characterize the network density.     

Determination of multipolymer structure using pyrolysis gas chromatography

The thermal degradation of poly(styrene-butadiene-methylmethacrylate-butylacrylate)multipolymers has been investigated by Curie Point pyrolysis gas chromatography (PGC). Small multipolymer samples were pyrolysed in a stream of helium at 600° in a Curie Point pyrolyser directly connected to the gas chromatograph. The pyrolysis products were identified by mass spectrometry. The interpretation of each cluster of dimer and trimer peaks appearing on the chromatogram was carried out by using a statistical method (factor analysis) from which the molecular structure of the multipolymers was inferred.     

Poly-α-ester degradation studies. I. Introduction: Design and construction of equipment

The various types of polyester degradation known to occur at elevated temperature are briefly summarized with particular reference to features of potential diagnostic value. Although little is known of poly-α-ester degradation in particular, examination of work on other linear polyesters indicates the spectrum of analytical and kinetic information that will be needed to characterize the degradation of poly-α-esters of various structures. On the basis of this review, an apparatus has been designed which enables kinetic information to be simultaneously obtained by thermogravimetry, gas evolution analysis, and rheological studies of the residual polymer melt. In addition a gas sampling procedure enables twin-column gas-liquid chromatographic analysis to be carried out on the degradation products. Samples of the chromatographically separated degradation products are collected in a microcollector cell for infrared and mass spectrometric analysis. Other refinements include in-line filament and Curie-point pyrolysis techniques.     

Design and development of pyrolyser to extract medicinal oil from the stem of Ziziphus jujuba

Pyrolysis as an extraction method of phytochemicals from plant parts for medicinal applications is less explored. Practitioners of traditional Indian medicine use a process which is a crude equivalent of pyrolysis, to extract oily substances from stem parts of plants and use them in treatment of various ailments. In this study, a prototype pyrolyser is fabricated to simulate the traditional method and the stem part of Ziziphus jujuba is subjected to pyrolysis using the pyrolyser under controlled conditions. Based on the principle of applied pyrolysis, the engineering design is conceptualized and drawing for a prototype extractor is made. Material selection for the main reactor vessel and the heating system with controller is finalized. The prototype is fabricated. The oily extract obtained is compared with the extract from the traditional method for compositional identity and phyto chemistry to validate the process. The chemical similarities of the extracts from both methods establishes pyrolsis as the basic principle behind the traditional method and this validates the design of the pyrolyser. The FTIR and GC-MS analysis of the extracted oily substance from both methods reveals the presence of various cyclic, nitrogenous, long chain and heterocyclic compounds which are believed to be the pyrolysates of various cyclopeptide alkaloids reportedly present in the stem of Ziziphus jujuba. These phytochemicals have sedative property and are likely to be responsible for the curative nature of the oil used in the treatment of various human disorders and the research substantiates the stem's historical use by traditional practitioners.     

Mass spectrometric and factor discriminant analysis of complex organic matter from the bacterial culture environment of Bacteroides gingivalis

Curie point evaporation and pyrolysis mass spectrometry were applied to the analysis of samples from cultures of Bacteroides gingivalis, an anaerobic microorganism isolated from the dental sulcus of human patients. Gaseous metabolites were sampled on ferromagnetic wires with an absorbent coating of activated carbon. Smears of bacteria and media after growth were analysed on normal ferromagnetic wires. The mass spectra from analyses at the Curie-point temperatures of 358°C and 510°C were examined with a specially adapted factor discriminant analysis program based on ARTHUR. The bacteria were characterized mainly by their volatile fractious. Mass spectra of the media after growth reflected physiological differences between the strains. The absorbent wire technique proved useful for evaluation of gaseous metabolites. Curie-point evaporation and pyrolysis mass spectrometry was found to be especially useful for preliminary screening of samples of organic matter from the various compartments of the bacterial environment.     

Curie-point pyrolysis gas chromatography/mass spectrometry in the identification of paint media

Curie-point pyrolysis gas chromatography/mass spectrometry has been applied to different model paint samples containing proteinaceous (egg yolk) and oily (linseed oil) media. Results of pyrolysis at 610°C are highly reproducible, and among the different pyrolysis products some compounds diagnostic for the different binders have been identified. The application of the method to real samples, i.e. from the oil painting ‘Ritratto’ by Giuseppe Nogari (1669–1763) and from the tempera paint on the ligneous roof of S. Giobbe church (16th century) in Venice, proves its effectiveness in the identification of binding media.     

Applications of a new vapour-phase pyrolyser

The application of a device for the post-column vapour-phase pyrolysis of compounds after gas chromatographic separation is described. The system proposed permits a mixture to be separated, pyrolysis to be carried out and pyrograms to be obtained in the chromatograph with one flame ionization detector. The reproducibility of the retention time and the intensity of the pyrogram peaks were studied. Some examples of applications to the identification of unknown components in a single gas chromatographic analysis are given.     

Coupling of thermal desorption in modified closeable sampling columns with wide-bore capillary gas chromatography and mass spectrometric detection

In contrast to usability of Curie-point pyrolysis at 700°C directly attached to gas chromatography-mass spectrometry (GC-MS) for determination of organic wood preservatives in waste wood samples the investigation method reported here consists of thermal desorption at temperatures about 260°C in connection with GC-MS for peak identification or GC with flame ionization detection for quantitative analyses. So-called “modified closeable sampling columns” are used as batch-reactor in thermal desorption experiments. Desorbed vapours can be introduced on capillary columns without sample discrimination and without a disturbing lost of resolution. In this manner a lot of individual polycyclic aromatic hydrocarbons were determinated in waste wood samples, especially in railway sleepers.     

全盘自动化气相色谱仪单纯形寻优

自行研制的全盘自动化气相色谱仪在通用计算机的支持下,通过单纯形自动寻优,在色谱专家水平上建立了分析样品的最佳气相色谱分析方法。