Emission rates of VOC from paper versus cellulose degradation: an integrated approach to paper characterisation

International audienceThe aim of this ongoing research is to investigate possible correlations between two levels of chemical degradation of cellulose, i.e. the macromolecular level, particular to the polymer, and the molecular level, which leads to the formation of volatile organic compounds (VOC), end-products from oxidation and hydrolysis reactions of cellulose. The objective of developing an integrated approach for evaluating paper degradation is also to establish novel non-destructive stategies for the diagnostic of the conservation state of works on paper. Size-Exclusion Chromatography with Multiangle Laser Light Scattering (SEC/MALS) was used for the macromolecular characterisation of cellulose in model papers, unaged and artificially aged [1]. Indeed, ultimately it is the average length of the cellulose molecules that governs the physical properties of paper, which are related to the material mechanical resistance and brittleness. However, even working on a micro-destructive scale, SEC/MALS analysis requires sampling, which can become problematic in light of the cultural value of paper documents. The VOC production of the model papers, and especially their emission rates, were studied using Field Laboratory Emission Cells (FLEC) [2]. The VOCs were gathered using Solid Phase Extraction (SPE) on two specific sorbent packings, 2,4-Dinitrophenylhydrazine (DNPH) derivatised silica and Tenax TA. The analysis of the VOCs was carried out with either Liquid Chromatography (LC/UV) or Thermal Desorption and Gas Chromatography with dual detection of Flame Ionisation and Mass Spectrometry (TD-GC/FID/MS). These techniques allowed to bypass physical sampling. Capillary Zone Electrophoresis (CZE/UV) was also used to identify and quantify small organic acids and carbohydrates in the papers in order to correlate the results with those of the emission rates. The techniques developed led to the identification of numerous VOC from paper and the determination of their emission rates. Among the most abundant compounds (eg. furfural and other heterocycles, formaldehyde, formic acid, acetic acid, vanillin,...) some showed a linear production during accelerated ageing, and others displayed a more complex evolution, which will be discussed in light of the degradation state