Confirming the Limitations of Diffusive Sampling using Tenax TA during Long Term Monitoring of the Environment

Abstract

In order to assess the ideal range of volatile organic compounds (VOCs) that can be quantitatively retained by Tenax TA during long term environmental diffusion monitoring and obtain an estimate of any sampling bias that maybe present, an experiment was devised whereby long term diffusive monitoring, using 7 and 14 day exposure times, was compared to time integrated daily diffusive sampling, conducted in parallel, for the same period of time. Some of the VOCs sampled for were ideal for use with Tenax TA whilst others, with greater volatility, were chosen for their expected non-ideal behaviour. The experiment was carried out for 3 outdoor and 4 indoor environments. The results clearly show that mass uptake for the most volatile species declines as the exposure time increases relative to the time integrated data. A comparison between time weighted average (TWA) concentration data, calculated using effective mass uptake rates, confirms that a negative sampling bias will be incurred in extending the exposure time for the sampling analytes considered unsuitable for collection on Tenax TA. However this bias becomes negligible at very low exposure concentrations such as those encountered during outdoor environmental monitoring.