Pyrolysis - mass spectrometry

Pyrolysis mass spectrometry (PyMS) is a technique that (via Curie-point pyrolysis) thermally degrades a sample of interest at a known temperature in an inert atmosphere or a vacuum. It causes molecules to cleave at their weakest points to produce smaller, volatile fragments called pyrolysate (Irwin, 1982). The mass spectrometer can then be used to separate the 

In Curie-point pyrolysis the material is placed on an iron-nickel alloy foil which is heated to the Curie point of the foil (this is 530°C for 50 50 Fe-Ni foils). For a given type of foil, the Curie-point temperature is constant, therefore this type of pyrolysis is very reproducible. The foil holding the sample is rapidly heated to its Curie point by passing a radio-frequency current for 3 s (in the case of the Horizon 200-X instrument used at Aberystwyth) through a coil surrounding the foil. The foil takes around 0.5 s to reach this point at this temperature the material on the foil is thermally 

One of the great advantages of PyMS is that it is relatively cheap compared with other methods of analysis. Many samples can be run through the PyMS machine in a short time (typically less than 2 min each) at a cost of less than 1 sterling per sample. 

The atomic masses up to 50 are discarded since they include very common compounds such as methane (CH4,16 amu), ammonia (NH3,17 amu), water (H2O, 18 amu), methanol (CH3OH, 32 amu) and hydrogen sulphide (H2S, 34amu), which are likely to be present in large quantities in any pyrolysate. Fragments with an miz ratio of over 200 are rarely analytically important for bacterial discrimination so these are also discarded (Good- 

Spectroscopic and Structural Characterization 3.4.3.1 Pyrolysis-Mass Spectrometry 

Information regarding the chemical identity of gases evolved from specimens as a function of the heating temperature can be obtained from pyrolysis-mass 

The most important conclusions emerging from these studies may be summarized as follows  

The magnitude of the peak associated with the methoxy group (m/z = 31) was negligible as compared with that of benzene or its derivatives. Flence, the major thermal decomposition pathway up to Tp of about 500 °C involves the cleavage of the complete meso-substituent and not just the outer fringe of the chelate as reported originally by van Veen et al. [131] 

The high molecular weight volatile fragments detected for H2TM PP and to a much lesser extent for (FeTMPP)20 are ascribed to species involving both pyrrole and substituted phenyl moieties. 

The system was used to study a wide range of polymeric materials. The sensitivity is sufficiently high to allow samples of 5 ug or less to give adequate electron-impact spectra, but in the chemical ionisation mode larger samples are necessary. Mass pyrograms are usually characteristic of the sample type and frequently allow discrimination between samples of similar composition. 

Jackson and Walker studied the applicability of pyrolysis combined with capillary column gas chromatography mass spectrometry to the examination of phenyl polymers (eg. styrene-isoprene copolymer) and polymer like phenyl ethers (eg. bis(m-(m-phenoxy phenoxy)phenyl)ether). They examined the effect of varying parameters affecting the nature of products formed and relative product distribution in routine pyrolysis. These parameters include the effects of pyrolysis temperature rise times, pyrolysis temperatures up to 985 C and pyrolysis duration. Temperature rise time (0.1 to 1.5 s) is not a critical factor in the Curie point pyrolysis of a styrene-isoprene copolymer, either with regard to the nature of the products formed or their relative distributions. Additionally, the variation of pyrolysis duration or hold time (2.0 to 12.5 s) at a fixed Curie temperature reflected no change in the nature of components formed however changes in product distributions were observed. Variations in Curie temperature at a fixed pyrolysis duration produced drastic changes in product distributions such as a three- 

A pyrogram of the copolymer (isoprene-styrene) resulting from a 10 s pyrolysis at 601°C yields product distributions similar to the sum of the two constituent product distributions. For example, when the polymer polyisoprene is pyrolyzed, C2, C3, C4, isoprene and Cjo dimers are produced. When polystyrene is pyrolyzed, styrene and aromatic hydrocarbons are the products. The copolymer product distribution and relative area basis resemble the two individual polymer product distributions. 

Mattem et al carried out laser mass spectrometry on polytetrafluoroethylenes. They found a fragmentation mechanism common to each fluoropolymer yields structurally relevant ions indicative of the orientation of monomer units within the polymer chain. A unique set of structural fragments distinguished the positive ion spectra of each homopolymer, allowing identification. 

Chin-An-Hu has described a pyrolysis mass spectrometric method for polymer characterisation. 

The enormous tenperatures attained on resistively heated sanple holders can also be used to intentionally enforce the deconposition of nonvolatile sanples, thereby yielding characteristic pyrolysis products. Pyrolysis mass spectrometry (Py-MS) can be applied to synthetic polymers [40], fossil biomaterial [41], food [42], and soil [43] analysis and even to characterize whole bacteria [44]. In polymer analysis, for example, Py-MS does of course not yield molecular weight distributions, though the type of polymer and the monomer units it is based on can usually be identified by Py-MS [40,45]. Often, pyrolysis products are not directly introduced into the ion source but separated by GC beforehand. A detailed treatment of this branch of mass spectrometry is beyond the scope of the present book. 

The advantages of PMS over PGC for generating information about polymeric materials are its speed, sensitivity, ease of producing data that can be processed by a computer, and the elimination of the variables associated with GC. A major disadvantage of PMS is that a complex mixture is produced by a combination of pyrolysis and electron impact fragmentation, which makes a mass pyrogram more difficult to interpret than the chromatogram produced in PGC, in which only a pyrolytic breakdown is involved. 

The in-source direct PMS method discussed in Section 3.8.2 [9] when used in conjunction with a spectral library search is capable of providing rapid identification of some iso polymers. 

Infrared (IR) spectra of thin films of a polymer in the region up to 4000 cm are characteristic of the polymer. Computerised retrieval from data in a library of standard polymers has been used in the IR fingerprinting technique to facilitate polymer identification [10]. 

Alexander [11] has described a method for obtaining spectra of thin films of polymer that are free of interference fringes. 

The method has been described extensively in previous papers (ref. 358,359). The extract (1 mg) was suspended in methanol (1 ml) by mild ultrasonic treatment. From this suspension, 5-pl samples were applied to ferromagnetic coated wires and the solvent was evaporated under rotation. The coated wires were mounted in glass reaction tubes. The automated pyrolysis mass spectrometry 

Polymer pyrolysates may be rather complex for example, the pyrogram of 1,4-polybutadiene contains some 500 components [670], complicating considerably the application of PyGC (unless comprehensive) as well as PyMS techniques. To ease the 

PyMS is a mass spectrometric technique in which a flash pyrolysis device is coupled directly or indirectly to a mass spectrometer. Total PyMS experiments can be performed in a few minutes. Off-line PyMS of polymers was first reported in 1948 [671, 672] and on-line PyMS of polymers in 1953 [673]. In the ideal experimental design the pyrolytic fragments of macromolecules are generated under non-isothermal conditions, escape sufficiently fast from the dissociating matrix so that overheating and further rearrangement of the pyrolysis products are prevented, and are analysed without further wall contact by soft ionisation MS techniques. The ideal conditions are most closely met when pyrolysis takes place inside the ionisation chamber, but in practice the analytical PyMS conditions are often quite different. 

PyMS systems eliminate some of the problems associated with transfer of pyrolysis products from 

Several advanced PyMS configurations have been described. Boon et al. [712] have presented a multi-purpose external ion source FTICR mass spectrometer for rapid microscale analysis of complex mixtures. External source DT-FTlCR-MS allows obtaining nominal mass spectra, temperature windows, HRMS data and exact elemental composition and MS/MS data on selected ions. For more detailed structural analysis of the more volatile part of the pyrolysate PyGC-MS and PyGC-HRMS are frequently applied. Laser pyrolysis experiments benefit 

Hummel [691] has given an excellent account of Py-FIMS in polymer studies, which contains much information of mechanistic and stmctural value, in spite of the simplicity of the spectra. The use of insource pyrolysis coupled with FIMS for studies of 

The use of GC-MS grew rapidly during the early 1970s as discussed by Shackleford and McGuire [1]. 

The advantages of Py-MS over pyrolysis-gas chromatography (Py-GC) for generating information about polymeric materials are its speed, sensitivity, ease of producing data 

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Laser desorption is commonly used for pyrolysis/mass spectrometry, in which small samples are heated very rapidly to high temperatures to vaporize them before they are ionized. In this application of lasers, very small samples are used, and the intention is not simply to vaporize intact molecules but also to cause characteristic degradation. 

Pyrolysis mass spectrometry, which does not require a volatile derivative, has been applied to various penicillins (78MI51100). These spectra contained fragments arising from the bicyclic ring system (4,5-dihydro-5,5-dimethylthiazole at mje 115, 1- and 2-methylpyrrole at mje 81 and unidentified peaks at m/e 100 and 125) as well as a series of fragments characteristic of the C(6) side chain. 

R. Goodacre, D.B. Kell and G. Bianchi, Rapid identification of species using pyrolysis mass spectrometry and artificial neural networks of propionibacterium acnes isolated from dogs. J. Appl. Bacteriol., 76 (1994) 124-134. 

R. Goodacre, J. Pygall and D.B. Kell, Plant seed classification using pyrolysis mass spectrometry with unsupervised learning the application of auto-associative and Kohonen artificial neural networks. Chemom. Intell. Lab. Syst., 33 (1996) 69-83. 

R. Goodacre, Characterisation and quantification of microbial systems using pyrolysis mass spectrometry introducing neural networks to analytical pyrolysis, Microbiol. (Europe), 2 19 (1994). 

T-MS). The main direct mass-spectral methods are thermal desorption and pyrolysis mass spectrometry. Several factors favour the efficiency at which volatiles can be removed from a polymeric matrix ... 

PyMS Pyrolysis mass spectrometry SALS Small-angle light scattering... 

Pyrolysis Mass Spectrometry of Recent and Fossil Biomaterials. Compendium and Atlas... 

Wright, M. and B. Wheals (1987), Pyrolysis-mass spectrometry of natural gums, resins and waxes and its use for detecting such materials in ancient Egyptian cases, /. Appl. Pyrol. 11,195-211. 

Basile, F. Voorhees, K. J. I Iadfield.T. L. Microorganism Gram-type differentiation based on pyrolysis mass-spectrometry of bacterial fatty-acid methyl-ester extracts. Appl. Environ. Microbiol. 1995, 61,1534-1539. 

METHOD REPRODUCIBILITY AND SPECTRAL LIBRARY ASSEMBLY FOR RAPID BACTERIAL CHARACTERIZATION BY METASTABLE ATOM BOMBARDMENT PYROLYSIS MASS SPECTROMETRY... 

Cartmill,T. D. Orr, K. Freeman, R. Sisson, P. R. Lightfoot,N. F. Nosocomial infection with Clostridium difficile investigated by pyrolysis mass spectrometry. J. Med. Microbiol. 1992,37, 352-356. 

Freeman, R. Gould, F. K. Wilkinson, R. Ward, A. C. Lightfoot, N. F. Sisson, P. R. Rapid inter-strain comparison by pyrolysis mass spectrometry of coagulase-negative staphylococci from persistent CAPD peritonitits. Epidemiol. Infect. 1991, 106,239-246. 

Sisson, P. R. Kramer, J. M. Brett, M. M. Freeman, R. Gilbert, R. J. Lightfoot, N. F. Application of pyrolysis mass spectrometry to the investigation of outbreaks of food poisoning and non-gastrointestinal infection associated with Bacillus species and Clostridium perfringens. Int. J. Food Microbiol. 1992,17, 57-66. 

Beverly, M. B. Basile, F. Voorhees, K. J. Fatty acid analysis of beer spoiling microorganisms using pyrolysis mass spectrometry. J. Am. Soc. Brewing Chemists 1997, 55,79-82. 

Goodacre, R. Trew, S. Wrigley-Jones, C. Neal, M. J. Maddock, J. Ottley, T. W. Porter, N. Kell, D. B. Rapid screening for metabolite overproduction in fermentor broths using pyrolysis mass spectrometry with multivariate calibration and artificial neural networks. Biotechnol. Bioengin. 1994, 44,1205-1216. 

Goodacre, R. Karim, A. Kaderbhai, M. A. Kell, D. B. Rapid and quantitative analysis of recombinant protein expression using pyrolysis mass spectrometry and artificial neural networks Application to mammalian cytochrome b5 in Escherichia coli. J. Biotechnol. 1994,34,185-193. 

Goodacre, R. Kell, D. B. Pyrolysis mass spectrometry and its applications in biotechnology. Curr. Opin. Biotechnol. 1996,7, 20-28. 

Goodacre, R. Shann, B. Gilbert, R. J. Timmis, E. M. McGovern, A. C. Alsberg, B. K. Kell, D. B. Logan, N. A. Detection of the dipicolinic acid biomarker in Bacillus spores using Curie-point pyrolysis mass spectrometry and fourier transform infrared spectroscopy Anal. Chem. 2000,72,119-127. 

DISCRIMINATION AND IDENTIFICATION OF MICROORGANISMS BY PYROLYSIS MASS SPECTROMETRY FROM BURNING AMBITIONS TO COOLING EMBERS—A HISTORICAL PERSPECTIVE... 

With recent developments in analytical instrumentation these criteria are being increasingly fulfilled by physicochemical spectroscopic approaches, often referred to as whole-organism fingerprinting methods.910 Such methods involve the concurrent measurement of large numbers of spectral characters that together reflect the overall cell composition. Examples of the most popular methods used in the 20th century include pyrolysis mass spectrometry (PyMS),11,12 Fourier transform-infrared spectrometry (FT-IR), and UV resonance Raman spectroscopy.16,17 The PyMS technique... 

Flowchart showing the main stages in pyrolysis mass spectrometry. 

Meuzelaar, H. L. Kistemaker, P. G. A technique for fast and reproducible fingerprinting of bacteria by pyrolysis mass spectrometry. Anal. Chem. 1973, 45, 587-590. 

Meuzelaar, H. L. C. Haverkamp, J. Hileman, F. D. Pyrolysis Mass Spectrometry of Recent and Fossil Biomaterials. Amsterdam Elsevier, 1982. 

Windig, W. Kistemaker, P. G. Haverkamp, J. Factor analysis of the influence of changes in experimental conditions in pyrolysis-mass spectrometry. J. Anal. Appl. Pyrolysis 1980, 2,7-18. 

Gutteridge, C. S. Characterization of microorganisms by pyrolysis mass spectrometry. Meth. Microbiol. 1987,19, 227-272. 

Meuzelaar, H. L. Kistemaker, R G. Eshuis, W. Boerboom, H. A. Automated pyrolysis-mass spectrometry application to the differentiation of microorganisms. Adv. Mass Spectrom. 1976, 7B, 1452-1456. 

Wieten, G Haverkamp, J. Meuzelaar, H. Boudewijn Engel, H. Berwald, L. Pyrolysis mass spectrometry A new method to differentiate between the mycobacteria of the tuberculosis complex and other mycobacteria. J. Gen. Microbiol. 1981,122,109-118. 

Borst, J. van der Snee-Enkellar, A. C. Meuzelaar, H. L. C. Typing of Neisseria gonnorrhoeae by pyrolysis mass spectrometry. Antonie van Leewenhoek 1978,44, 253. 

Kajioka, R. Tang, P W. Curie-point pyrolysis mass-spectrometry of Legionella species. /. Anal. Appl. Pyrolysis 1984, 6, 59-68. 

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