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Partition coefficient

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Description of key information

Key value for chemical safety assessment

at the temperature of:
20 °C

Additional information

The octanol/water partition coefficient (P) of the test compound, di(2-ethylhexyl)terephthalate also known as DOTP, was determined through shake-flask batch extraction and gas-liquid chromatography (GLC) using procedures equivalent to OECD 107 guidelines. Triplicate GLC analyses of duplicate 0.1% and 1% DOTP-in-octanol samples yielded a mean P value of 5.2 X 105 for well water (log Pow = 5.72), with a relative standard deviation (RSD) of 60%. The mean P value in sea water was found to be 1.8 X 105 (log Pow = 5.26), with an RSD of 19%. However, for this substance it is recognized that the shake-flask method does not adequately distinguish between test substance that is truly in water solution and that which may be suspended in micelles and trace particulate matter in water, which would lead to an erroneously high measured concentration in the water phase and an underestimation of the actual Kow.

The studies were performed before the development of the slow-stir methodology (OECD 123) which eliminates this problem. Therefore these studies are believed to be unreliable. Estimations of the log Kow were performed using 3 different well recognized models, SPARC, KOWIN, and ACD Labs. These models provided log Kow values for this substance of 7.81, 8.39, and 9.54 respectively. This endpoint is provided as a range of these values using a weight of evidence approach. Of these values the value generated by KOWIN, log Kow = 8.34, provides a estimated water solubility value from the WSKOW model that is consistent with the experimentally derived water solubility value determined by a slow-stir technique similar to the methods used in OECD 123. Therefore, greater confidence is placed on that value being the best estimate of Kow for this substance.