Measuring Diffusive Uptake Rates of VOCs on Thermal Desorption Diffusive Air Samplers for Use in Human Health Risk Assessment

Abstract:

Sampling by axial tube sorbent samplers is a convenient and reliable method of air analysis. This technique collects compounds of interest by pumping air through the sampler (active sampling) or by the diffusion of those compounds across the ambient air/sorbent concentration gradient (diffusive sampling). Determining compound concentrations from diffusive sampling requires the use of a diffusive uptake rate. This proves problematic for the quantification of compounds sampled as published uptake rates in the relevant literature are sparse. A parallel active/diffusive sampling technique on Tenax® TA was employed to measure uptake rates. Samples were then analyzed via thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) for desired analytes, in this case VOCs including BTEX and other hydrocarbons. For uptake rates representing sample durations of one week or more, rates of shorter duration were compiled and utilized. A developed literature on diffusive uptake rates would provide currently unavailable insight into the risk certain compounds pose to human health. Diffusive sampling offers average concentrations over the entirety of a sampling period which lends a truer expression of long-term exposure humans experience to these compounds and thus alludes to the potential risk to human health as a result.