Determination Of Low-Density Polyethylene-Water Partition Coefficients For Novel Halogenated Flame Retardants With The Large Volume Model And Co-Solvent Model

The partition coefficient (K-pew) of an analyte between low-density polyethylene (LDPE) film and water is a critical parameter for measuring freely dissolved concentrations of the analyte with PE passive sampling devices. Measuring log K-pew for super hydrophobic organic chemicals (HOCs) have been proven extremely difficult. The present study developed a large volume model for measuring log K-pew of super HOCs, i.e., novel halogenated flame retardants (NHFRs). Results showed that the measured log K-pew values of selected PAHs and PCBs obtained by the large volume model were in line with those from the co-solvent model and the literature data within less 0.3 log units of difference, while those of NHFRs (6.27-7.34) except for hexachlorocyclopentadienyldibromocyclooctane (HCDBCO) and Decabromodiphenyl ethane (DBDPE) were significantly lower than those (6.51-8.89) from the co-solvent model. A curvilinear relationship was observed between log K-pew and log K-ow of all target compounds, with the turning point at log K-ow = similar to 8.0 in the large volume model, but that was not found for the co-solvent model. These can be attributed to the large molecular volumes (> 450 angstrom(3)) for NHFRs, which require high Gibbs free energy to penetrate into the inside structures of LDPE in the large volume model. However, the solvent swelling effects in the co-solvent model needs to be investigated. Therefore, the large volume model is robust to determine the K-pew values of super HOCs for facilitating the application of aquatic passive sampling techniques. (C) 2021 Elsevier Ltd. All rights reserved.