As early as 1952, Zemany (ref. 1) pioneered the application of pyrolysis mass spectrometry (Py-MS) to the characterisation of biopolymers such as albumin and pepsin. Although he employed a relatively primitive off-line filament pyrolysis technique, his results showed that characteristic and reproducible fingerprints could be obtained. After Zemany's publi cation, no further Py-MS studies of biomaterials appear to have been reported for more than a decade. Instead, two years later Davison, Slaney and Wragg (ref. 2) published the first account of a different analytical pyrolysis technique, namely pyrolysis gas chromatography (Py-GC), which required less expensive and complicated instrumentation than Py-MS and soon found application in the synthetic polymer field and a number of related areas. In the early 1960's, the search for extraterrestrial life - or, at least, complex organic compounds - as part of the scientific mission of planned space probes prompted the application of Py-GC to biochemical problems, e.g., studies of biopolymers and microorganisms by Wilson et al. (ref. 3) and Oyama (ref. 4). This, in turn, triggered an extensive series of studies by Reiner et al. (refs. 5-7), who pioneered the application of Py-GC in microbiology.
Meanwhile, Zemany's report on Py-MS seemed almost forgotten, in spite of the strong potential advantages of Py-MS over Py-GC with regard to speed of analysis, long-term reproducibility and suitability of the data for computer processing. Towards the end of the 1960's, however, scattered reports on the use of direct Py-MS for the characterisation of complex organic materials appeared in the literature. Hummel's group in Cologne started an impressive series of experiments (refs. 8, 9) using both direct probe and filament pyrolysis in combination with field ionisation and electron impact ionization mass spectrometry for structural elucidation of synthetic polymers. Also, publications dealing with biochemical applications of Py-MS appeared, revealing the existence of at least three different pyrolysis approaches namely, direct probe pyrolysis, laser pyrolysis and filament pyrolysis. This diversification reflected the existence of the same three approaches in Py-GC since direct probe pyrolysis, using a heated capillary, can be regarded as the equivalent of "oven" or "furnace" pyrolysis in Py-GC. For a detailed account of the development of pyrolysis techniques up to 1967, the reader is referred to the excellent review by Levy (ref. 10). Developments up to 1979 are described in two highly detailed and complete reviews by Irwin and Slack (ref. 11) and Irwin (ref. 12), which should be consulted by every worker in the field of analytical pyrolysis. Since the above three pyrolysis approaches still persist in Py-MS today, the further evolution of these techniques will be discussed in the following paragraphs.
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