Volatile Organic Compounds (VOCs) in Books - Research Project Outline

The aim of this project is to identify and quantify the range of volatile organic compounds emitted by paper as it ages, and to relate the data to the fibre furnish used to make the paper and to its mode and degree of degradation. On the basis of this it should be possible to identify specific markers or combinations of compounds that will characterise different sources of fibre, the principal mode of degradation (acid hydrolysis or oxidation) and the extent of degradation (pH or carbonyl content). It would then be possible to construct an analytical tool that would give a non-destructive indication of the condition of the books in a store simply by sampling the air.

All paper emits a complex mixture of organic compounds as it ages, including the volatile acids formic and acetic acid. These contribute to the familiar "smell of old books" (Buchbauer et al 1995, Lattuati-Derieux et al 2004). There are two principal pathways for degradation of cellulose: acid-catalysed hydrolysis, which predominates at lower temperatures, and oxidation, which predominates at higher temperatures. Acid hydrolysis leads to breaking of the cellulose chains and emission of materials such as furfural (Baranski, Lagan and Lojewski 2004), while oxidation leads to the formation of carbonyls and the emission of volatile acids such as formic and acetic as well as non-volatile acids including oxalic and lactic (Strlic et al 2004). Degradation of lignin-containing papers contributes a range of aromatic compounds, including acids. The mix of compounds produced depends on the nature of the paper, the degree of degradation, and the pathway by which it is degrading (Doering et al 2001). Already more than 100 different compounds, including acids, aldehydes, alcohols, ketones, alkanes and terpenes, have been identified in books and paper, so the challenge is to identify those which are most significant. This list can be compared with those compounds previously identified in wooden display cases (Stulik and Grzywacz 1992).

In well-ventilated or air-conditioned stores, these substances are quickly dissipated, but in areas where air exchange is limited to ensure environmental stability, they may accumulate and contribute to further acid-catalysed hydrolysis. There may also be health implications for people who work in storage areas, if ventilation rates are low. This is being investigated by Havermans as part of the PaperTreat project. Experiments at the Library of Congress show that even new, alkaline paper produces acids quite rapidly during natural ageing (Shahani and Harrison 2002). This problem is therefore not confined to old books printed on poor-quality paper, but may also affect modern books printed on acid-free paper. This project will quantify the rate at which acids are formed in books and paper of different ages and compositions, and the proportion that is retained within the books (where it may contribute to further hydrolysis of cellulose) and that which is emitted to the air, where it may contribute to the degradation of other, non-acidic, books. Measurement of the quantity and chemical nature of the volatile compounds in the air in a store will therefore give an indication of the condition of the books in that room.

The laboratory tests will combine destructive analysis and quantification of acids by ion chromatography with non-destructive analysis using solid-phase micro-extraction (SPME) and gas chromatography. The emphasis throughout will be on quantification rather than the simple identification of volatiles. The use of a non-destructive technique means that it will be possible to quantify the acidic degradation products in collection items in ambient storage conditions and thus obtain a realistic indication of their rate of deterioration. The ratios of different degradation products will indicate the relative importance of acid hydrolysis and oxidation for each book or paper type, and thus indicate what kind of preventive treatment will have the greatest influence on their life-cycle.

Field studies will measure the concentrations of volatile acids in the air in different locations in various book stores in the six Legal Deposit Libraries and two national archives, using diffusion tubes. This simple but reliable technique has been widely used in museums to measure acidic pollutants and is appropriate for this study. Preliminary experiments suggest that newspapers emit acid at a rate of the order of 10µg per cubic metre per day, and these measurements, combined with those of the amount of acid extracted from paper, will indicate how much is lost to the environment and how much is retained in the paper. The nature and condition of the collection in each location and its ventilation rate will determine the nature and concentration of volatile compounds in the air.

Further laboratory tests will reveal the extent and the rate at which books made of acid-free and alkaline buffered paper will absorb volatile acids when present in the atmosphere at known concentrations. This will demonstrate how much of a threat acidic books are to their non-acidic neighbours, and provide a justification for segregating them in stores.

References

Baranski, A, Lagan, J. M. and Lojewski, T. (2004), Acid-catalysed degradation, in Ageing and Stabilisation of Paper, ed. Strlic, M and Kolar, J, Ljubljana : National and University Library of Slovenia, 93-109.

Buchbauer, G, Jirovetz, M, Wasicky, M and Nikiforov, A (1995), On the odour of old books, J Pulp Paper Science ( 21 ) 398-400.

Doering, T, Fischer, P., Banik, G., Binder, U. and Liers, J. (2001), An approach to evaluate the condition of paper by a non-destructive analytical method, Adv. Printing Science and Technology ( 27 ) 27-39.

Lattuati-Derieux, A., Bonnassies-Termes, S. and Lavédrine, B. (2004), Identification of volatile organic compounds emitted by a naturally aged book using solid-phase microextraction / gas chromatography / mass spectrometry, J. Chromatography A ( 1026 ) 9-18.

Shahani, C. J. and Harrison, G. (2002), Spontaneous formation of acids in the natural aging of paper, in Works of Art on Paper, Books, Documents and Photographs: Techniques and Conservation, ed. Daniels, V., Donnithorne, A. and Smith, P., London : IIC, 189-192.

Strlic, M, Kolar, J., Kocar, D. and Rychly, J. (2004), Thermo-oxidative degradation, in Ageing and Stabilisation of Paper, ed. Strlic, M and Kolar, J, Ljubljana: National and University Library of Slovenia, 111-132.

Stulik, D. and Grzywacz, C. (1992), Carbonyl pollutants in the museum environment: an integrated approach to the problem, in La Conservation Préventive, ARAAFU: Paris, 199-205.

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