Comics’ VOC-abulary: Study of the ageing of comic books in archival bags through VOCs profiling

In the last years, the price of several collectible comic books reached the record value of millions of dollars. Since the value of collectible comic books is strictly related to their state of preservation, specialized rating agencies certificate their quality and condition, and for the same reason comics books are commonly encapsulated in sealed containers or bags for preservation and protection. Nonetheless, recent studies regarding micro-climate frames for the exhibition or storage of artworks as paintings suggest that the storage of any composite object made of organic materials in a sealed environment could lead to the presence of a significant concentration of volatile organic compounds (VOCs) in the enclosed micro-climate, that can be related to unexpected degradation pathways, or to an increase in the ageing rate of materials. In this study, we characterized the volatile organic compounds (VOCs) emitted by comic books stored in archival bags for the first time in the literature. In particular, we analyzed the VOCs emitted by comic books printed in the last six years by the same publisher. We applied solid phase micro extraction (SPME) to characterize the VOCs profile inside archival bags containing comic books by gas chromatography/mass spectrometry (GC/MS). The semi-quantitative data obtained on more than 60 individual VOCs were elaborated by principal component analysis (PCA) allowing us to highlight a variation in the profiles of the emissions of the series of comics books printed from 2012 to 2018 and stored in sealed archival bags immediately after the purchase. Select ion flow tube mass spectrometry (SIFT-MS) was also used to obtain quantitative results in real time, as an alternative to the SPME sampling step. This study represents the first reported application of SIFT-MS in heritage science. The study contributed to identify VOC profiles and molecular markers that can be used to study the emission of comic books in sealed bags, and can ultimately be correlated to the degradation processes of the materials used in their production.