Jacek,

Sorry for the late response, I did not see your question before today.

Headspace equilibrium SPME in negligible depletion mode ( http://pubs.acs.org/doi/abs/10.1021/ac061880o ) could be a good option for sampling VOCs from soils, but this depends on the desired measurement endpoint. This approach is simple to operate and automate, and it can provide precise measurements of fugacity, chemical activity and/or freely dissolved concentrations (calibration to total concentrations would require stable isotope labeled standards). Such equilibrium sampling is based on the equilibrium partitioning into an absorptive coating (PDMS), which makes the approach very robust against variations in sampling kinetics and also robust against competitive sorption and saturation phenomena. Such equilibrium sampling with SPME and also other equilibrium sampling devices (polymer sheets, coated jars, etc.) are presently gaining ground within the assessment and management of polluted sediments, because many risk processes are closer related to chemical activity than to total concentrations. For instance, the equilibrium partitioning concentrations in animal lipids can be predicted with such methods, see e.g.:

https://www.researchgate.net/publication/49698808_Equilibrium_sampling_of_persistent_and_bioaccumulative_compounds_in_soil_and_sediment_comparison_of_two_approaches_to_determine_equilibrium_partitioning_concentrations_in_lipids?ev=prf_pub

There has been a SETAC workshop in California in 2012 on the application of such sampling techniques to contaminated sediments, and the resulting papers are presently in press.

Best regards

Philipp

Article Equilibrium Sampling of Persistent and Bioaccumulative Compo...