Lipid-water partition coefficients and correlations with uptakes by algae of organic compounds

In view of the scarcity of the lipid-water partition coefficients (K_tw) for organic compounds, the logK_tw values for many environmental contaminants were measured using ultra-pure triolein as the model lipid. Classes of compounds studied include alkyl benzenes, halogenated benzenes, short-chain chlorinated hydrocarbons, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and organochlorine pesticides. In addition to logK_tw determination, the uptakes of these compounds from water by a dry algal species were measured to evaluate the lipid effect on the algal uptake. The measured logK_tw are closely related to their respective logK_ow (octanol-water), with logK_ow=1.9 to 6.5. A significant difference is observed between the present and early measured logK_tw for compounds with logK_ow>~5, which is attributed to the presence and absence of a triolein microemulsion in water affecting the solute partitioning. The observed lipid-normalized algae-water distribution coefficients (logK_aw/lipid) are virtually identical to the respective logK_tw values, which manifests the dominant lipid-partition effect of the compounds with algae.