title: Determining chemical activity of (semi)volatile compounds by headspace solid-phase microextraction.
abstract: This research introduces a new analytical methodology for measuring chemical activity of nonpolar (semi)volatile organic compounds in different sample matrices using automated solid-phase microextraction (SPME). The chemical activity of an analyte is known to determine its equilibrium concentration in the SPME fiber coating. On this basis, SPME was utilized for the analytical determination of chemical activity, fugacity, and freely dissolved concentration using these steps: (1) a sample is brought into a vial, (2) the SPME fiber is introduced into the headspace and equilibrated with the sample, (3) the SPME fiber is injected into the GC for thermal desorption and analysis, and (4) the method is calibrated by SPME above partitioning standards in methanol. Model substances were BTEX, naphthalene, and alkanes, which were measured in a variety of sample types: liquid polydimethylsiloxane (PDMS), wood, soil, and nonaqueous phase liquid (NAPL). Variable sample types (i.e., matrices) had no influence on sampling kinetics because diffusion through the headspace was rate limiting for the overall sampling process. Sampling time was 30 min, and relative standard deviations were generally below 5% for homogeneous solutions and somewhat higher for soil and NAPL. This type of activity measurement is fast, reliable, almost solvent free, and applicable for mixed-media sampling.
authors.affiliation: Department of Environmental Chemistry and Microbiology, National Environmental Research Institute, University of Aarhus, Frederiksborgvej 399, 4000 Roskilde, Denmark. chni@dmu.dk
authors.forename: Charlotte N
authors.initials: CN
authors.lastname: Legind
authors.forename: Ulrich
authors.initials: U
authors.lastname: Karlson
authors.forename: Joel G
authors.initials: JG
authors.lastname: Burken
authors.forename: Fredrik
authors.initials: F
authors.lastname: Reichenberg
authors.forename: Philipp
authors.initials: P
authors.lastname: Mayer