Measurements of octanol-air partition coefficients for polychlorinated biphenyls

The octanol-air partition coefficient, K-OA, is measured for 15 polychlorinated biphenyls (PCBs) over the temperature range -10 degrees C to +30 degrees C using a generator column method. The enthalpy of phase change from octanol to air, Delta(O)(A)H, is calculated for 18 PCBs and ranges from 66 to 90 kJ/mol. Enthalpy of dissolution of the liquid phase PCB in octanol, Delta(SOL)H, calculated as Delta(VAP)H - Delta(O)(A)H, has a mean value of 6.6 kJ/mol (n = 18) and there is no correlation of Delta(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(L)(O)) 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.