EMISSION OF ORGANIC ACIDS FROM WOODEN CONSTRUCTION MATERIALS IN A SMALL TEST CHAMBER; PRELIMINARY RESULTS OF OPTIMISATION OF THE SOLID PHASE MICRO EXTRACTION TECHNIQUE

Maarten van Bommel, Bart van Elst, and Francien Broekens

Instituut Collectie Nederland / Netherlands Institute for Cultural Heritage (ICN)

PART 1: ABSTRACT

Wooden construction materials, used in storage and exhibitions, are known sources for low molecular organic volatiles. The amount of organic volatiles depends, among others, on the type of wood. Especially particleboard and other composits such as MDF, are known to emit formic acid, acetic acid and formaldehyde, but other types of wood emit these organic compounds as well. In the last decades, much effort has been put in determining the effects of these emissions on objects of culture and art, e.g. by the well-known "Oddy test". Furthermore, methods to reduce emission have been investigated. Appropriate lacquers, absorption materials or sealing the wood with impermeable films can reduce the emission significantly.

The damage to objects depends on the concentration of harmful gasses, the sensitivity of the material of the object, exposure time and environmental conditions. In the case of organic acid vapours and formaldehyde, the wooden construction material of the showcase is often the emitting source. The concentration organic volatiles do not only depend on the emission rate of the construction material, but also on the ventilation of the showcase. A high air exchange rate will in principle lower the concentration organic vapour, assuming that the outside air does not contain organic vapour. However, the exchange rate does also affect the emission rate of the construction material; a higher exchange rate will increase the emission.

At the ICN, research is focussed on predicting the final concentration of organic vapours in a showcase, in order to provide guidelines for the use of construction materials and the need of mitigation methods. For this, it is necessary to determine the emission rates of materials at different exchange rates. Usually, construction materials are placed into a small test chamber with the possibility to control the air exchange rate by flushing the test chamber with a variable airflow. The concentration organic vapours in the air is determined using various sampling and analysis techniques, however, none of these techniques is satisfactory in terms of sensitivity and speed. Lately, a new sampling technique, Solid Phase Micro Extraction (SPME), is introduced as a fast and sensitive method.

This presentation focuses on the sampling technique itself, in particular on establishing the relationship between the uptake by the SPME fibre and the flow rate of the air. Using a calibration gas, two different sampling techniques were compared: static and dynamic sampling. Static sampling is performed by flushing a glass jar with the calibration gas. Next, the glass jar is closed and the SPME fibre is introduced through a septum and exposed to the stagnant air. The advantage of this technique is that the sampling rate of the SPME fibre is independent of the airflow. Dynamic sampling is performed by sampling directly in the gas stream through an in-line injection valve. This presentation discusses the application of different SPME fibres, the effect of the airflow rate during SPME sampling on the amount of organic vapour collected, evaluation of the different sampling techniques and the calibration of the sampling technique used.

Click here for Part 2: Slides from presentation

Author to whom correspondence may be addressed:

Maarten van Bommel
Instituut Collectie Nederland
Gabriel Metsustraat 8
1071 EA Amsterdam
The Netherlands
E-mail: Maarten.van.Bommel@icn.nl