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Partition coefficient

Description of key information

Octanol/water partition coefficient (Log Pow): 1.12 (calculated using Chemsilico software)

Key value for chemical safety assessment

Log Kow (Log Pow):

1.12

Additional information

Experimental determination of the partition coefficient was commissioned but a result was not obtained for the following reasons:

As the test item was not applicable to the partition coefficient test, no determination was carried out using Method A8 Partition Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008, Method l07 of the OECD Guidelines for Testing of Chemicals, 27 July 1995 or Method ll7 of the OECD Guidelines for Testing of Chemicals, 13 April 2004. The following reasons are given:

• As the test item was a complex mixture of a metal oxide with organic ligands, it was considered not applicable to the HPLC method as the reference standards detailed in the guidelines are not of similar chemical classes. Therefore, correlation to the calibration plot would be subject to significant error.
• Although a single preliminary sample was attempted, this indicated the shake-flask method was not applicable. It was observed that the test item was removed from the organic phase by centrifugation indicating it was a suspension and not a true solution. lf a lower stock solution concentration was prepared to dissolve all the test item, this may be too low to measure a reliable partition coefficient.
• In combination with only having a non-specific analytical method and the shake-flask method not being ideal for mixtures, the analysis results for the organic and aqueous phases may have been for different components of the test item that have significantly different partition coefficients. This is especially the case with there being organic and inorganic components in the test item.
• Also, it would not be possible to calculate a partition coefficient based on the solubility of the test item in water and n-octanol for two reasons. Firstly, as both analytical methods used to measure the water solubility were not test item specific and only one of these could be used for n-octanol, it would be subject to error to compare the solubilities in the two solvents and be analyte selective. Additionally, although it was noticed the test item was a suspension in n-octanol at lower concentrations, at very high concentrations it appeared the test item was miscible with n-octanol. These would both lead to doubts over any result. Therefore, an accurate and reliable partition coefficient result was considered not possible. It can only be anticipated that the test item would favor the organic phase over the aqueous phase as very high concentrations were possible in n-octanol but not in water.