Pyrolysis - gas chromatography - mass spectrometry

Sharp and Paterson [41] have described a pyrolysis - gas chromatographic - mass spectrometric procedure for the determination of 1-10% of copolymerised acrylic acid and methacrylic acid in acrylic polymers (see Method 3.5). The acid groups are propylated and the polymer pyrolysed according to the following reaction scheme  

Jander and co-workers [42] used PyGC to characterise carbonyl groups in humic substances. 

The incorporation of a gas chromatography (GC) stage between pyrolysis (Py) and mass spectrometry (MS) has the obvious advantage of refining the detail that can be achieved in structural analysis and rendering MS identification of pyrolysis prodncts more certain. The application of Py-GC-MS to the identification of complex mixtnres of volatile compounds produced under high temperature conditions has been reviewed by Chang and Tackett [1]. 

Not unlike TG-MS cfr. Chp. 2.1.5.3), PyGC cfr. Chp. 2.2.1) and PyMS cfr. Chp. 2.2.2), PyGC-MS represents a vast number of instrumental configurations differing in pyrolyser type, PyGC interface, GC characteristics (column type), MS characteristics (including ionisation mode), operational variables (oxidative pyrolysis, simultaneous alkylation pyrolysis, temperature-resolved pyrolysis, etc.) and data handling procedures (search library, chemomet-rics). Standardisation in this area is still far off. 

On- and off-line PyGC-MS approaches were discussed by Boon [708]. The first directly coupled PyGC-MS system, using a Curie-point pyrolyser, was described by Simon et al. [762]. The use of flash pyrolysis has increased dramatically with introduction of fused silica GC columns. In PyGC-MS the type of ionisation mode is usually either El or CL Electron impact ionisation at the normal ionising voltage (70 eV) causes extensive fragmentation. 

Additive detection with PyGC-MS is influenced by (i) fragmentation or thermal stability of the additive (ii) concentration of the additive in the matrix (Hi) structure (mass) of additive and polymer fragments (specificity) and (iv) reactions of additive and polymer fragments. 

Before analysing polymer samples it is useful to examine first the pyrolysis behaviour of the pure additives. For example, pyrolysis of A/ -isopropyl-A -phenyl-/7-phenylenediamine (IPPD) at 550°C leads to the formation of A -phenyl-p-phenylenediamine 

In case of great similarity in chemical structures of additive and polymer fragments it is no longer possible to identify the additive fragment 

Pyrolysis - gas chromatography has been used for many years for the characterisation of plastics materials, particularly when they are of an intractable nature owing to cross-linking or are very heavily filled. The technique has now been extended to include mass spectrometry and is of particular value when minor components need to be identified. An example has been described by Sharp and Paterson for the identification of small amounts (1-10%) of copolymerised imsaturated acids in acrylic polymers. The method can be summarised as follows  

The copolymerised acid is propylated by treatment of the sample with Propyl 8 reagent, the resultant polymer is pyrolysed and the propyl ester of the acid, if present, is identified by gas chromatography - mass spectrometry. By this procedure copolymerised acrylic or methacrylic acid has been identified in terpolymers with (a) butyl acrylate and styrene, (b) methyl methacrylate and ethyl acrylate and (c) ethylene and propylene. A methyl methacrylate - alpha-methylstryene - maleic acid terpolymer, when examined by 

Py-GC employing various detection systems is the technique usually used to qualitatively and quantitatively analyse major components and low-level additives in polymers [1-3]. The technique utilises thermal energy to break down polymers to monomers and small oligomers. The mixture of pyrolysis products is directly passed into a gas chromatograph (GC) for separation. However, there are numerous low-level co-monomers and additives that may not be appropriately separated at the same time as the major monomers. These low-level co-monomers and additives frequently appear with poor peak shape under the chromatographic conditions established for analysis of the major monomers hence the interest in combining this technique with MS (such as a polar additive in a non-polar capillary colnmn). Additionally, these peaks may have been overlooked because they exist as converted products in the chromatogram after the pyrolysis-induced reaction (such as vinyl acetate converted to acetic acid). 

Ogawa and co-workers [4] used Py-GC-MS to analyse the components of ozone deteriorated nitrile-butadiene rubber sheet containing additives. There were three peaks related to the quinoline antioxidant in the program. They noted that the mechanical strength of the sheet became zero when the antioxidant level reached 50% of its original level. 

Franich and co-workers [5] described two simple methods using internal standards for the quantitative analysis of 2,6-di- er -butyl-4-methylphenol (butylated hydroxy toluene, BHT) antioxidant in samples of solvent-formulated liquid adhesive and in cured polychloroprene adhesive films. Because only very small samples of cured adhesive could be taken from articles or components without substantially detracting from the product, the methods were developed to use minimal quantities of cured adhesive. The Py-GC method required 

In contrast to the Py-GC method, the extraction method showed only two peaks in the chromatogram, for the internal standard (10.4 min) and the BHT (12.2 min). The resolution and integration facility of the peaks were excellent. 

Wang and co-workers [6] used a Py-GC technique for the qualitative analysis of fumaric acid and itaconic acid as low-level monomers polymerised with other major monomers in emulsion styrene maleic anhydride co-polymers. In order for fumaric acid and itaconic acid to be detected through pyrolysis, the acids are derivatised with primary amines such as methylamine and ethylamine to form a cyclic imide. The detection of derivatised fumaric acid and itaconic acid was accomplished by atomic emission detection. The structures of the derivatisation-pyrolysis products were elucidated by MS. 

When polymers are burnt or smoulder in air, the combustion products are extremely complex, often consisting of several hundred compounds. Because of the toxic or unknown nature of these products, it is important to know their composition in some detail. This information is also essential for mechanistic and modelling studies of the smoke formation process, which can lead to the design of less hazardous polymers in the future. 

A number of analytical methods [66, 67] involving pyrolysis of polymers have been reported in the literature. Michal and co-workers [68] developed a method using direct gas chromatography (GC)-mass spectrometry (MS) for their study of the combustion of polyethylene (PE) and PP. Morikawa [69] used GC to determine polycyclic aromatic hydrocarbons in the combustion of polymers. Liao and Browner [70] also described a method for the determination of polycyclic aromatic hydrocarbons. Many other workers have studied soot and smoke formation and their mechanisms in the combustion of polymers. Generally in these studies, relatively simple and specific methods were used, which were appropriate for the intended tasks. However, these methods are not suitable for complete analysis of the very complex smoke particulates resulting from combustion of many polymers. Most methods have been developed either for volatile compounds of low molecular weight or for polycyclic aromatic hydrocarbons. Joseph and Browner [71] developed a method that can be used to 

The method is directed towards the particulates produced and excludes the volatile compounds of very low molecular weight. Smoke particulates from the smouldering of PU foam in air were collected on glass fibre filters and extracted with chloroform. The concentrated extract was subjected to acid and base extractions. The acid compounds were converted to methyl esters and analysed by a GC-MS data system. The basic and phenolic compounds were analysed using the same system without derivatisation. The neutral fractions were separated into different classes by high-performance liquid chromatography on a bonded amine column. Different fractions were collected and each fraction was analysed by GC-MS with data collection. 

Some nitrogen containing compounds were identified in the neutral fractions. There were five-membered nitrogen containing ring compounds, including indole, isoxazole, indazole, and carbazoles which do not show basic properties and consequently do not react with 1 M hydrochloric acid in the basic extraction step. A number of phthalate esters were also present in different fractions. 

When pyrolysis is carried out at 150 °C the components occurring at the maximum concentration in the hydrocarbon region are located in the C23 region for virgin linear low-density polyethylene (LLLDPE), LDPE - 50% magnesium hydroxide and LLDPE - 40% magnesium hydroxide - 10% red phosphorus. 

Springer Series in Wood Science Methods in Lignin Chemistry (Edited by S.Y. Lin and C.W. Dence) 

Lignin classification based on the quantities of the three phenylpropanoid units, namely 4-hydroxyphenylpropane (H), guaiacylpropane (G), and syringylpropane (S), formed in the pyrolysis of lignocellulosic materials 

Microanalysis of lignin in wood cells and cell fragments of different morphological origin 

Fingerprinting and identification of technical lignins from various pulping processes 

The use of GC-MS grew rapidly during the early 1970s as discussed by Shackleford and McGuire [105]. 

There are now several suppliers of equipment for carrying out this technique (see Appendix 1). One supplier is Finnigan MAT, which supplies single-stage quadruple mass spectrometers. 

1 SSQ70 Series Single-Stage Quadrupole Mass Spectrometer 

In high-performance MS-MS (as opposed to GC-MS) the separator as well as the analysis is performed by the mass spectrometer. One advantage of this technique over combined chromatography-mass spectrometry is that separation is a spatial process rather than being dependent on time. This can lead to improved analysis times and/or greater specificity. MS-MS also opens up other areas such as the study of complete structures. 

3 H-SQ30 Hybrid Mass Spectrometer-Mass Spectrometer 

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G. Chiavari, N. Gandini, P. Russo, D. Fabbri, Characterisation of standard tempera painting layers containing proteinaceous binders by pyrolysis gas chromatography mass spectrometry, Chromatographia, 47, 420 426 (1998). 

Bonaduce I., Colombini M.P., Characterisation of beeswax in works of art by gas chromato graphy mass spectrometry and pyrolysis gas chromatography mass spectrometry procedures, Journal of Chromatography A, 2004, 1028, 297 306. 

N. Gallois, J. Templier and S. Derenne, Pyrolysis gas chromatography mass spectrometry of the 20 protein amino acids in the presence of TMAH, J. Anal. Appl. Pyrol., 80, 216 230... 

M. Carbini, R. Stevanato, M. Rovea, P. Traldi and D. Favretto, Curie point pyrolysis gas chromatography/mass spectrometry in the art field. 2. The characterization of proteinaceous binders, Rapid Commun. Mass Spectrom., 10, 1240 1242 (1996). 

H. Ling, N. Maiqian, G. Chiavari and R. Mazzeo, Analytical characterization of binding medium used in ancient Chinese artworks by pyrolysis gas chromatography/mass spectrometry, Microchem. J., 85, 347 353 (2007). 

L. Osete Cortina and M.T. Domenech Carbo, Analytical characterization of diterpenoid resins present in pictorial varnishes using pyrolysis gas chromatography mass spectrometry with on line trimethylsilylation, J. Chromatogr., A, 1065, 265 278 (2005). 

K.B. Anderson and R.E. Winans, Nature and fate of natural resins in the geosphere. I. Evaluation of pyrolysis gas chromatography mass spectrometry for the analysis of natural resins and... 

M.J. Casas Catalan and M.T. Domenech Carbo, Identification of natural dyes used in works of art by pyrolysis gas chromatography/mass spectrometry combined with in situ trimethylsilyla tion, Anal. Bioanal. Chem., 382, 259 268 (2005). 

H. Mestdagh, C. Rolando, M. Sablier and J. P. Rioux, Characterization of ketone resins by pyrolysis gas chromatography/mass spectrometry, Anal. Chem., 64, 2221 2226 (1992). 

Techniques are available to quantify the generation of smoke, toxic and corrosive fire products using the NBS Smoke Chamber (15), pyrolysis-gas chromatography/mass spectrometry (PY-GC-MS) (J 6), FMRC Flammability Apparatus (2,3,5,17,18), OSU Heat Release Rate Apparatus (13) and the NIST Cone Calorimeter (JJO. Techniques are also available to assess generation of 1) toxic compounds in terms of animal response (19), and 2) corrosive compounds in terms of metal corrosion (J 7). In the study, FMRC techniques and AMTL PY-GC-MS techniques were used. 

Pyrolysis-Gas Chromatography-Mass Spectrometry. In the experiments, about 2 mg of sample was pyrolyzed at 900°C in flowing helium using a Chemical Data System (CDS) Platinum Coil Pyrolysis Probe controlled by a CDS Model 122 Pyroprobe in normal mode. Products were separated on a 12 meter fused capillary column with a cross-linked poly (dimethylsilicone) stationary phase. The GC column was temperature programmed from -50 to 300°C. Individual compounds were identified with a Hewlett Packard (HP) Model 5995C low resolution quadruple GC/MS System. Data acquisition and reduction were performed on the HP 100 E-series computer running revision E RTE-6/VM software. 

Characterization of Their Sources by Low-Level Radiocarbon Counting and Pyrolysis/Gas Chromatography/Mass Spectrometry, Conference on Carbonaceous Particles in the Atmosphere, T. Novakov, ed., University of California, Berkeley, p. 36, 1978. 

Thermogravimetric methods such as pyrolysis gas chromatography-mass spectrometry have been used to characterize hydrocarbon sludges from polluted soils [10]. In combination with conventional extraction and supercritical fluid extraction followed by gas chromatography-mass spectrometry, over 100 constituents were identified in soil samples. Thermogravimetric analysis-mass spectrometric results distinguished between the release of a component by thermosorption and by pyrolysis. 

Figure 2.2 shows the total ion current trace and a number of appropriate mass chromatograms obtained from the pyrolysis gas chromatography-mass spectrometry analysis of the polluted soil sample. The upper trace represents a part of the total ion current magnified eight times. The peak numbers correspond with the numbers mentioned in Table 2.1 and refer to the identified compounds. The identification was based on manual comparison of mass spectra and relative gas chromatographic retention times with literature data [34, 35] and with data of standards available. In some cases unknown compounds were tentatively identified on the basis of a priori interpretation of their mass spectra (labelled tentative in Table 2.1). 

Thomas etal. [72] used pyrolysis gas chromatography-mass spectrometry as a fast economic screening technique for polyaromatic hydrocarbons. Thomas used reverse-phase liquid chromatography with atmospheric pressure chemical ionization mass spectrometry/mass spectrometry for the determination of polycyclic aromatic sulphur heterocycles in sediments. 

Schulten et al. [16] identified the following N-containing compounds in NH-N fractions separated from several soils by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) pyrrole (la), methyl pyrrole (lb), pyridine (IVa), methylpyridine (IVb), indole (Via), and benzothiazole (XI). The Roman numerals refer to the chem-... 

Pyrolysis-field ionization mass spectrometry (Py-FIMS) and Curie-point pyrolysis-gas chromatography/mass spectrometry (CpPy-CC/MS) of soils... 

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