Updated Abraham Solvation Parameters for Polychlorinated Biphenyls

This study shows that the recently published polychlorinated biphenyl (PCB) Abraham solvation parameters predict PCB air-n-hexadecane and n-octanol-water partition coefficients very poorly, especially for highly ortho-chlorinated congeners. Therefore, an updated set of PCB solvation parameters was derived from four PCB properties and associated Abraham solvation equations. Additionally,the influence of ortho-chlorination on PCB solvent accessible volume and surface area was investigated. The updated PCB solvation parameters were tested on partitioning between five other phase combinations. Compared to the original PCB solvation parameter set, the updated PCB solvation parameters resulted in substantially improved estimates from Abraham solvation equations for (subcooled) liquid vapor pressures, aqueous solubilities, HPLC capacity factors, and for coefficients of air-n-hexadecane, air-water, organic carbon-water, and n-octanol-water partitioning. For water to polydimethyl siloxane and sodium dodecylsulphate (SDS) partitioning, the updated PCB solvation parameters yielded no improvement compared to the original data set The main difference between the updated and the original parameter set is that updated PCB McGowan specific volumes depend on the degree of ortho-chlorination, which is qualitatively confirmed by trends in the PCB solvent accessible volumes and surface areas. The use of the updated PCB solvation parameters instead of the original values is therefore recommended.