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(38-43) SPME-measurements of freely dissolved concentration of hydrophobic organic compounds in the Microtox Solid Phase test. ter Laak, T. L.*,1, Mayer, P.2, Busser, F.1, Klamer, J. C.3, Hermens, J. L. M.1, 1 University of Utrecht, Utrecht, The Netherlands2 TNO, Delft, The Netherlands3 RIKZ, Haren, The Netherlands ABSTRACT- The Microtox Solid Phase (MSP) sediment toxicity test was developed to determine the acute toxicity of contaminated sediments. In this test, Vibrio fisheri, a luminescent marine bacterium, is added to a range dilutions of a sediment suspension. It is generally thought that (test) organisms (insects, oligochaetes and bacteria) are exposed to contaminants via the water-phase. This research aims to investigate the freely dissolved (bioavailable) concentrations of different hydrophobic organic chemicals (HOCs) in the MSP-test system. 'Free concentrations' of a selection of organic contaminants were measured with a 7 Key words: Sediment Sorption, SPME, Free dissolved concentration, Hydrophobic organic chemicals |
m Polydimethylsiloxane (PDMS) SPME-fiber after 126 hours incubation. These included a number of chlorobenzenes, chloroanilines and chloronitrobenzenes in spiked sediment and a number of chlorobenzenes in field sediment. Dissolved concentration measurements were plotted against the sediment suspension-dilution factor, showing free concentrations to be stable at low dilution factors and decreasing at higher dilution factors. The initial stability can be explained by a partition-controlled delivery from the sediment that keeps the aqueous concentration constant. Dissolved concentration measurements were fitted by non-linear regression in order to determine sediment/water partition coefficients. These regressions do illustrate how concentrations of compounds change non-linearly and how the composition of the mixture changes with dilution as well.