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Partition coefficient

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No determination of the partition coefficient was possible since (benzoato-O,O')hydroxy(octadecanoato-O,O')aluminium is an ionisable salt and the partition coefficient can vary greatly depending on pH and the pKa of the substance. The substance could not be tested as it is insoluble in water and is expected to be insoluble in n-octanol. Exposure to the substance is not expected as it is embedded in an oil matrix.

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No determination of the partition coefficient was possible by the shake-flask method as detailed in Method A8 Partition Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 107 of the OECD Guidelines for Testing of Chemicals, 27 July 1995. This was due to the insolubility of (benzoato-O,O')hydroxy(octadecanoato-O,O')aluminium in water, as determined to be less than 0.000025 g/L (WIL 2016) and the expected insolubility in n-octanol based on read-across from aluminum, benzoate C16-18-fatty acids complexes. Further to this, determination of the partition coefficient by the HPLC estimation method as detailed in Method A8 Partition Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 117 of the OECD Guidelines for Testing of Chemicals, 13 April 2004, was also not possible. (benzoato-O,O')hydroxy(octadecanoato-O,O')aluminium is expected to be insoluble in suitable reverse phase HPLC solvents, based on the insolubility of the read-across substance, aluminum, benzoate C16-18-fatty acids complexes.

The partition coefficient was estimated by QSAR but the result is considered not to be relevant to the substance itself. As (benzoato-O,O')hydroxy(octadecanoato-O,O')aluminium is an ionisable salt, the partition coefficient can vary greatly depending on pH and the pKa of the substance. In order to compare partition coefficient values of different, ionisable compounds on a relative basis, partition coefficient values are sometimes reported as "corrected for ionisation", indicating that the value represents the partition coefficient at a pH where a compound exists primarily in the non-ionised form. However, KOWWIN (KOWWIN v1.68 in EPISuite v4.00, US EPA 2009) considers (benzoato-O,O')hydroxy(octadecanoato-O,O')aluminium to be “ion pairs” and as such only provides estimates for the ionised fatty acids and benzoic acid rather than the salt. The partition coefficient value for the salt itself therefore could not be determined.

(Benzoato-O,O')hydroxy(octadecanoato-O,O')aluminium is typically not synthesized as the “pure” compound and seldom exists except in the presence of the oil matrix. High temperature stability indicates that the grease thickener structure is robust and resistant to diffusion out of the oil. Dissolution of the grease thickener from grease into water is very unlikely as the thickener is poorly water soluble and the thickener is embedded in the hydrophobic grease matrix and is designed not to leach out. Thus the partition coefficient of the substance is not expected to be relevant.