Applicability of passive sampling to bioanalytical screening of bioaccumulative chemicals in marine wildlife

Quantification of bioaccumulative contaminants in biota is time and cost-intensive and the required extensive cleanup steps make it selective toward targeted chemical groups. Therefore tissue extracts prepared for chemical analysis are not amenable to assess the combined effects of unresolved complex mixtures. Passive equilibrium sampling with polydimethylsiloxane (PDMS) has the potential for unbiased sampling of mixtures, and the PDMS extracts can be directly dosed into cell-based bioassays. The passive sampling approach was tested by exposing PDMS to lipid-rich tissue (dugong blubber; 85% lipid) spiked with a known mixture of hydrophobic contaminants (five congeners of tetra- to octachloro-dibenzo-p-dioxins). The equilibrium was attained within 24 h. Lipid-PDMS partition coefficients (Klip-PDMS) ranged from 20 to 38, were independent of hydrophobicity, and within the range of those previously measured for organochlorine compounds. To test if passive sampling can be combined with bioanalysis without the need for chemical cleanup, spiked blubber-PDMS extracts were dosed into the CAFLUX bioassay, which specifically targets dioxin-like chemicals. Small quantities of lipids coextracted by the PDMS were found to affect the kinetics in the regularly applied 24-h bioassay; however, this effect was eliminated by a longer exposure period (72 h). The validated method was applied to 11 unspiked dugong blubber samples with known (native) dioxin concentrations. These results provide the first proof of concept for linking passive sampling of lipid-rich tissue with cell-based bioassays, and could be further extended to other lipid rich species and a wider range of bioanalytical end points.