Expanding the Applicability Range of the Generator Column Technique to Measure the Octanol-Air Partition Ratio of Volatile Compounds

Bioaccumulation modeling has identified a lower limit of similar to 5 for the log of the octanol-air partition ratio (log KOA) of chemicals that potentially bioaccumulate in air-breathing organisms. Because existing techniques are not well suited to this volatility range (vapor pressure between 1 and 1000 Pa), we adjusted the generator column method to allow for KOA determination of more volatile compounds. We reduced gas flow rates and experimental run times and examined the potential depletion of octanol within the generator column. By recording KOA values for hexachlorobenzene, 1,2,3,4-tetrachlorobenzene, and 1,2,3-trichlorobenzene that agree with earlier measurements, we first confirmed our ability to obtain reliable data with the generator column technique. The log KOA values between 5 and 45 degrees C for 1,3-dichlorobenzene, trans-decalin, 2,6-dimethyldecane, 1,2,3,4-tetramethylbenzene, hexylcyclohexane, tri-isopropyl phosphate, and tetradecene have been obtained with the technique. The lowest log10 KOA value measured was 4.69 for trans-decalin at 25 degrees C. Good agreement with predictions made with poly-parameter linear free energy relationships lends confidence to these data. Reducing gas flow rates and experimental run times are key to obtaining reliable KOA data when applying the generator column technique to volatile compounds. Depletion of the octanol concentration in the generator column did not notably affect the KOA obtained from the measurements.

Automated summary

Bioaccumulation modeling has identified a lower limit for the log KOA values of chemicals that potentially bioaccumulate in air-breathing organisms. We adjusted the generator column method to determine KOA values of volatile compounds and successfully obtained reliable data. These findings have implications in assessing the bioaccumulation potential of different chemicals.