Determining the chemical activity of hydrophobic organic compounds in soil using polymer coated vials

Fredrik Reichenberg¹^,2 , Foppe Smedes³ , Jan-Åke Jönsson² and Philipp Mayer¹

¹Department of Environmental Chemistry and Microbiology, National Environmental Research Institute, University of Aarhus, PO Box 358, 4000 Roskilde, Denmark

²Division of Analytical Chemistry, Lund University, PO Box 124, S-221 00 Lund, Sweden

³Ministry of Transport, Public Works and Water management, National Institute for Costal and Marine Management/RIKZ, PO Box 207, 9750 AE Haren, Netherlands

author email corresponding author email

Chemistry Central Journal 2008, 2:8doi:10.1186/1752-153X-2-8


Published:	6 May 2008

Abstract

Background

In soils contaminated by hydrophobic organic compounds, the concentrations are less indicative of potential exposure and distribution than are the associated chemical activities, fugacities and freely dissolved concentrations. The latter can be measured by diffusive sampling into thin layers of polymer, as in, for example, solid phase micro-extraction. Such measurements require equilibrium partitioning of analytes into the polymer while ensuring that the sample is not depleted. We introduce the validation of these requirements based on parallel sampling into polymer layers of different thicknesses.

Results

Equilibrium sampling devices were made by coating glass vials internally with 3–12 μm thick layers of polydimethylsiloxane (PDMS). These were filled with slurries of a polluted soil and gently agitated for 5 days. The concentrations of 7 polycyclic aromatic hydrocarbons (PAHs) in the PDMS were measured. Validation confirmed fulfilment of the equilibrium sampling requirements and high measurement precision. Finally, chemical activities of the PAHs in the soil were determined from their concentrations and activity coefficients in the PDMS.

Conclusion

PAHs' thermodynamic activities in a soil test material were determined via a method of uptake into PDMS. This can be used to assess chemical exposure and predict diffusion and partitioning processes.