A micro-sampling strategy for monitoring plastic degradation via volatile organic profiling using headspace-solid-phase microextraction GC-MS. Application to historical cellulose acetate negatives

The historical, symbolic, and material value of cultural heritage objects imposes strict limitations on sampling, requiring analytical strategies capable of examining minute samples with minimal or no destruction. While non-invasive and minimally invasive methods are well established for inorganic materials, the characterization of organic components remains challenging. Spectroscopic techniques have partly addressed this issue, but they are often limited by spectral complexity and matrix interferences. Sample preparation methods typically required prior to chromatographic analyses usually consume a significant portion of the available sample, hindering the application of complementary analytical techniques. Here, a micro-sampling approach coupled with headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) was adapted and evaluated for the first time. The methodology enables sequential analytical workflows in which the same micro-sample can be further analyzed by complementary techniques. To demonstrate its applicability, naturally aged cellulose acetate negatives from the National Historical Museum of Argentina (MHN) were investigated. An untargeted analytical strategy was used to comprehensively characterize volatile organic compound (VOC) emissions and correlate them with degradation stage and other material features. A total of 40 VOCs were consistently detected across all fiber coatings, providing a robust volatile signature for material characterization and degradation assessment. The PDMS fiber discriminated against degradation stages, whereas the PDMS/DVB fiber differentiated samples according to format (small vs. large negatives), suggesting that VOC profiles may also reflect differences in manufacturing processes, use history, or conservation treatments. These results demonstrate the potential of HS-SPME-GC-MS for the non-destructive characterization of heritage plastics and degradation assessment. Moreover, the proposed micro-sampling strategy is fully compatible with complementary analytical workflows, including cross-sectional and micro-spectroscopic analyses, providing a methodological framework for preventive conservation based on volatile degradation markers.