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(77-10) Equilibrium Sampling of Hydrophobic Organic Chemicals to Determine their Bioavailability. Mayer, Philipp*,1,2, Kraaij, Rik2, Vaes, Wouter2,3, Tolls, Johannes2, Hermens, Joop2, 1 National Environmental Research Institute, Roskilde, Denmark2 IRAS, Utrecht University, Utrecht, Netherlands3 TNO, Zeist, Netherlands ABSTRACT- Information about dissolved concentrations in addition to total concentrations is crucial for the understanding and the quantification of bioavailable pollutant fractions. Equilibrium partitioning methods are suited to measure dissolved concentrations in different environmental matrices including sediment, because analyte concentrations in the equilibrated sampling phase are controlled by the chemical potential (or fugacity) in the surrounding media (matrix). Dissolved concentrations can then be calculated using the appropriate partition coefficient. The principle of such equilibrium sampling methods will be described with emphasis on two crucial aspects: (1) Equilibrium extractions of hydrophobic organic substances are known to require long sampling times of up to tenth of years which limits their general applicability. The make-up of a fast sampler that allows equilibrium sampling within hours to weeks will therefore be discussed, and the importance of a high surface area to volume ratio will be addressed. (2) Exact and precise equilibrium partition coefficients are required in order to translate the measured analyte concentrations in the sampler to the surrounding media, and a simple method that is customized for this purpose will be presented. Finally, the applicability of dissolved concentrations within a bioavailability context will be demonstrated: contaminant concentrations in sediment dwelling worms will be predicted based on dissolved concentrations and bioconcentration factors, and these predicted concentrations will be compared with measured concentrations in the worms. Key words: Bioavailability, sediment, SPME, Equilibrium partitioning sampling, freely dissolved concentrations |
