Polymer-water partition coefficients of hydrophobic compounds for passive sampling: application of cosolvent models for validation.

Polymer-water partition coefficients (Kpw) of hexachlorobenzene, 41 polychlorinated biphenyls (PCBs), and 26 polyaromatic hydrocarbons (PAHs) were determined for low-density polyethylene (LDPE) and five different silicone rubbers. Partition coefficients were determined in ultra pure water and in a range of methanol-water mixtures. Different cosolvent models for the effect of methanol concentration on the polymer-mixture partition coefficient (Kpm) were used to validate the Kpw in pure water. Linear regression of logKpm against the mole fraction (x) methanol over range 0 < x < 0.3 yielded the best results. The obtained logKpws were best described by a correlation with molecular weight, for PCBs in combination with the fraction of chlorine atoms in the meta and para positions (standard deviations of approximately 0.08 log units). Correlations with logKow were less good (standard deviations of approximately 0.21 log units), partly as a result of uncertainties in the logKow estimates that were used. Similar Kpws were found for different batches of silicone rubber from the same supplier. Differences in logKpws for silicone rubbers obtained from different suppliers ranged from 0.16-0.58.