| Abstract: | SUMMARIES. This paper describes the application of pyrolysis-gas chromatography-mass spectrometry (PyGCMS) to the characterization of an extensive range of synthetic paint types. Household and industrial paints, both of which have been formulated with polymers such as alkyd, polyvinyl acetate (PVA) and nitro¬cellulose, are included in this study, in addition to the acrylic solution and acrylic emulsion paints that were made specifically for the artists ' market. The pyrograms obtained by PyGCMS were characteristic to each paint type and their principal diagnostic features are discussed. Apart from using the mass spectra produced by electron impact (El) to confirm the identity of every peak, two additional analytical features of the mass spectrometer were shown to be particularly useful in this study. Chemical ionization (CI) was used to assist with the identification of unknown peaks through molecular weight determination. Selected ion current (SIC) monitoring, where the mass spectrometer only scans for specific masses, was successfully used for the detec¬tion of peaks of low intensity or those hidden by a more abundant material with a similar retention time.
CONCLUSION. PyGCMS was shown to be an extremely effective analytical method for detecting all the principal classes of synthetic polymers that have been used as binding media in paint formulations. Each polymer class yielded a characteristic pyrogram, so that complicated co- and ter-polymers could be readily detected. The main limitation of the technique was the inability to carry out totally quantitative analy¬sis on any of the copolymers or mixtures of media, due to the occurrence of often quite complex frag¬mentation reactions on pyrolysis. The use of mass spectrometry as the detector, however, enabled the detection of weak or masked peaks and the use of mixed media by artists. Although not discussed here, the technique was just as suited to characteriz¬ing synthetic grounds and primers, which are for¬mulated with the same types of polymeric binder. It was also capable of detecting the main classes of resin used in synthetic varnishes as well as azo organic pigments. |
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