Non-Destructive Evaluation of Historical Paper Based on pH Estimation from VOC Emissions.

Matija Strlič,Gerrit De Bruin,Boris Pihlar,Irena Cigić,Jana Kolar

doi:10.3390/s7123136

Abstract

Volatile organic compounds (VOCs) emitted from materials during degradationcan be a valuable source of information. In this work, the emissions of furfural and aceticacid from cellulose were studied using solid-phase micro-extraction (SPME) incombination with gas chromatography-mass spectrometry. Two sampling techniques wereemployed: static headspace sampling using SPME for 1 h at 40 oC after 18-h samplepreparation at 80 oC in a closed glass vial, and contact SPME in a stack of paper (or abook). While a number of VOCs are emitted from paper under conditions of natural oraccelerated degradation, two compounds were confirmed to be of particular diagnosticvalue: acetic acid and furfural. The emissions of furfural are shown to correlate with pH ofthe cellulosic environment. Since pH is one of the most important parameters regardingdurability of this material, the developed method could be used for non-destructiveevaluation of historical paper.

Highlights

The analysis of historical objects is often difficult due to restricted sampling
The degradation pathway and the rate of chain scission depend on this parameter: in an acidic environment, cellulose degrades according to acidcatalysed hydrolysis, while in a moderately alkaline environment, it degrades through autoxidation
We developed a non-destructive approach for estimation of pH of historical paper using solid-phase micro-extraction and gas-chromatographic analysis with mass-spectrometric detection

Summary

Introduction

The analysis of historical objects is often difficult due to restricted sampling. The value of historical substance and its integrity is rarely outweighed by the information we gain through destructive sampling and subsequent chemical analysis. The degradation pathway and the rate of chain scission depend on this parameter: in an acidic environment, cellulose degrades according to acidcatalysed hydrolysis, while in a moderately alkaline environment, it degrades through autoxidation. The latter process is much slower and the lifetime of traditionally produced moderately alkaline paper (produced prior to ~1850) is thought to be several millennia. It was found out that the DVB/CAR/PDMS SPME fibre was the most appropriate for extraction of the variety of VOCs emitted from paper. It was our primary interest to relate the information on VOC emission, which can be obtained using contact-SPME sampling with chemical information on the emitting material. It turned out that contact SPME can be used to estimate the pH of paper in a non-destructive manner

Samples

Instrumentation

Static Headspace Sampling

Conclusions