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Reliable thermal mass quantification of PVC – An ongoing challenge
Summary
Researchers examined the challenges of reliably quantifying PVC using thermal analysis methods such as pyrolysis-gas chromatography-mass spectrometry, highlighting the complexity of pyrolytic processes and the susceptibility to matrix interference from organic compounds. They found that PVC is a particularly problematic candidate because its thermal decomposition products can originate from multiple sources, requiring careful contextual interpretation of results to avoid misidentification.
By now thermal analysis of micro- and nanoplastics has become a recognized, established and complementary alternative to spectroscopic methods. Pyrolytic methods are of particular advantage when it comes mass quantification at trace level and/or comparing results from different sample types in terms of space, time and modeling. Even though the method appears straightforward and is widely applied, pyrolytic processes are highly complex and susceptible to interferences. Accordingly, contextualized data interpretation is obligate and requires maximum attention. Especially if polymers are analyzed in complex samples according to indicative pyrolytic decomposition products and their related indicator ions are detected by mass spectrometry after gas chromatographic separation. Then, the signal obtained includes all copolymers and formulations that can be traced back to a respective base polymer. Consequently, the results obtained should be addressed as a (base) polymer cluster. The specificity of selected indicator products is decisive for the extent to which interference from organic accompanying matrix must be expected. Special attention require complex samples where the thermal decomposition products of a polymer may also have multiple sources. One particularly critical candidate is PVC. It has the third highest demand globally and is therefore of high analytical relevance. Thermal decomposition of PVC leads to extensive cleavage and releases HCl along with almost exclusively chlorine-free, partially alkylated aromatics available for polymer analysis. However, their lack of specificity lead to a challenge in data interpretation regardless of extensive sample pre-processing. The presentation will highlight polymers that contribute to the PVC cluster (C-PVC). Additionally, environmental relevant polymeric structures including refractive organic material will be shown, that hamper or restrict interpretation. It is discussed in which context meaningful results can be expected, when the inclusion of correction factors is appropriate to allow at least a semi-quantitative estimate and when an inclusion of C-PVC data should be completely questioned. Also see: https://micro2024.sciencesconf.org/558564/document