Introduction: We focus on organic acids emitted from wooden construction materials for showcases and cabinets
Concentration in showcases depends on the emission of objects,construction materials and outside sources. The ventilation influences the emission rate of construction materials. Due to ventilation, the final concentration gasses in the air will be lower (assuming that the construction material is the only source). However, the emission rate will be higher at higher ventilation.
Objectives give guidelines to the Museums
Aim of this research
The use of Solid Phase Micro Extraction for analysis: Compounds of interest absorb on the SPME fibre. Next the fibre is transferred to the injection port of Gas Chromatography-mass Spectrometry (GC-MS) and the compounds are desorbed due to the high temperature and analysed. See Supelco catalogue for more information (http://www.sigma-aldrich.com )
A small test chamber is used for measuring the construction material.
By varying the airflow, different ventilation rates are simulated. The air is sampled at the outlet by SPME.
Static sampling
Dynamic sampling
Measurements were performed using a calibration gas of acetic acid and formic acid.
Calibration gasses were made using permeation tubes.
Several SPME fibres were tested:
- PDMS / DVB polydimethylsiloxane / divinylbenzener
- CAR / PDMS Carboxen / polydimethylsiloxane
- CW / DVB Carbowax / divinylbenzene
- DVB / CAR / PDMS divinylbenzene / carboxen / polydimethylsiloxane
Comparison of dynamic and static measurements showed the response with dynamic sampling was higher. This is true for all four fibres tested
The uptake in dynamic sampling was not influenced by the flow rate of the air in the range tested, i.e. from 180 ml/min through 1500 ml/min. Therefore, static sampling was rejected. However, using flow rates lower than 180 ml/min might affect the sampling rate
Slide 13 through 16:
Uptake curves of the different fibres for acetic acid and formic acid. The more they absorb, the longer it takes to reach the equilibrium. The fibre with the highest uptake for both acids is the Carboxen / polydimethylsiloxane fibre.
Detection limits of all fibres when they are in equilibrium with the exception of the Carboxen / polydimethylsiloxane fibre where the sampling time is reduced to 30 min.
Calibration curves of formic acid and acetic acid with the Carboxen / polydimethylsiloxane fibre after 30 min. sampling.
Future research
The IAP group of the Instituut Collectie Nederland / Netherlands Institute for Cultural Heritage (ICN)
