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Environmental fate & pathways

Adsorption / desorption

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Description of key information

Modeled data is used to fulfill this endpoint as the physical/chemical properties of this substance prevented attempts to measure it experimentally.

Key value for chemical safety assessment

Additional information

A series of studies were performed to identify appropriate test system and analytical conditions for determining the adsorption/desorption (i.e., partitioning) of bis(2-ethylhexyl)terephthalate to soils and sediments. The experimental approach was based on OECD Test Guideline No. 106. In a preliminary study three sterilized soil types: Spodosol, Alfisol, and Entisol were utilized. In order to overcome the difficulty in measuring this substance in aqueous solution due to its extremely low waler solubility, a 14C isotope of the substance was used. The initial assessment of the analytical method for measuring the radio labeled substance in 0.01 M CaCl2 was performed. Using liquid scintillation counting, it was possible to measure the radio labeled substance at its limiting solubility and achieve recoveries of 95%-110%. Thereafter, a series of preliminary experiments were performed using varying compositions of soil, aqueous solution and test article. In these more complex systems, it was not possible to achieve good or reproducible recoveries of the radio labeled substance. Adsorption of the substance onto the surfaces of the glassware was a possible source of error. Deactivation of the glassware surfaces was attempted using sylilation, without success. Therefore, none of the test systems that were studied proved useful for performing adsorption/desportion, measurements. It was concluded that the high variation in the test system recoveries would not allow for adequate measurement of the adsorption/desorption characteristics of this test material. Due to the inability to determine this endpoint experimentally, the endpoint is fulfilled by weight of evidence using a range of values from QSAR estimations from three different methods. A log Koc value of 5.43 was obtained from the USEPA EPI Suite

KOCWIN QSAR model using a log Kow input of 8.39. Within the KOCWIN model a log Koc value of 5.07 was also obtained using the Molecular Connectivity Index Value method. A log Koc value of 6.6 was obtained using the ACDLabs model. Therfore, the log Koc is reported as being in the range of 5.07 to 6.6.