Measurements of Octanol−Air Partition Coefficients for Polychlorinated Biphenyls

Abstract

The octanol−air partition coefficient, K OA, is measured for 15 polychlorinated biphenyls (PCBs) over the temperature range −10 °C to +30 °C using a generator column method. The enthalpy of phase change from octanol to air, H, is calculated for 18 PCBs and ranges from 66 to 90 kJ/mol. Enthalpy of dissolution of the liquid phase PCB in octanol, Δ SOL H, calculated as Δ VAP H − H, has a mean value of 6.6 kJ/mol ( n = 18) and there is no correlation of Δ SOL H with homolog group or number of ortho-substituted chlorine atoms. Results show that K OA values increase within a homolog group for congeners having fewer ortho chlorine atoms. A log 10 − log 10 correlation of K OA against liquid-phase vapor pressure ( p o L ) shows enhanced partitioning into octanol for mono- and non-ortho congeners. Separate regressions for non/mono-ortho and multi-ortho groups allow K OA to be estimated for other congeners.