OCTANOL AIR PARTITIONING OF POLYCHLORINATED-BIPHENYLS/

The partitioning of 16 polychlorinated biphenyls (PCBs) between air an d 1-octanol was investigated using a fugacity meter. The measurements were conducted over an environmentally relevant temperature range (10- 43 degrees C). For a given congener the measured 1-octanol/air partiti on coefficient K-OA was exponentially proportional to the reciprocal t emperature. The enthalpy of phase change (octanol to air) Delta H-OA r anged from 71 to 93 kJ/mol. Up to log K-OA values of 9.37 (correspondi ng to 2,2',3,4',5',6-hexachlorobiphenyl), the enthalpy of phase change was similar to the enthalpy of vaporization of the subcooled liquid P CB. For the less volatile congeners (log K-OA > 9.37), the enthalpies of vaporization exceeded the enthalpies of phase change, the differenc e increasing with increasing log K-OA. Solubilities of the PCBs in 1-o ctanol were calculated from the data, and the results were in excellen t agreement with octanol solubilities calculated using the OCTASOL fra gment method. A very good correlation between the measured octanol/air partition coefficients and values calculated from octanol/water and a ir/water partition coefficients was obtained. This yielded a method to estimate reliably the octanol/air partitioning of all PCB congeners.