Solid-phase microextraction fibre–water distribution constants of more hydrophobic organic compounds and their correlations with octanol–water partition coefficients

Fibre coating–water distribution constants (Kfw) of more hydrophobic chemicals were determined with six different solid-phase microextraction fibre types (including a polyoctylmethylsiloxane (C8) prototype) by fibre exposure to agitated large-volume water samples lasting several days. The results obtained are comparable with Kfw values obtained under dynamic conditions. Octanol–water partition coefficients (Kow) were measured with the mixture of distributing substances to examine log Kfw–log Kow relationships based on a consistent dataset. Kfw values obtained with liquid polymer fibre coatings correlate reasonably well with the hydrophobicity of the test compounds (with decreasing sensitivity in the following order: 7 μm polydimethylsiloxane (PDMS)>100 μm PDMS>C8>polyacrylate) whereas this is not the case with the PDMS–divinylbenzene (DVB) and Carbowax–DVB fibres, partially porous coatings which provide the highest Kfw values for all substances tested.