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Physical & Chemical properties

Partition coefficient

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Description of key information

The structure-fragment calculation method indicates a log Pow range of -1.00 to -0.30 for components of this UVCB mixture. The upper limit value of log Pow = -0.30 is used to conservatively represent partitioning of the components of this UVCB substance in the chemical safety assessment (Dow, 2010).

Key value for chemical safety assessment

Log Kow (Log Pow):
-0.3
at the temperature of:
20 °C

Additional information

Octanol water partitioning of this UVCB mixture was investigated using the HPLC and shake-flask method (EU Method A.8) and under the conditions of the study, the partition coefficient n-octanol/water (log Pow) for components ranged from less than 0.3 to 1.6 (HPLC method) and by the shake-flask method was 0.0. In both cases, the results were suspected to be influenced by surface-active properties of the substance (surface tension = 38.4 nM/m at 20°C). Therefore, calculated values were generated for the lowest- and highest-molecular weight homologues of this mixture using the ClogP structure-fragment method. These calculated values indicate a log Pow range of -1.00 to -0.30 for this UVCB mixture. The upper limit value of log Pow = -0.30 is used to conservatively represent partitioning of the components of this UVCB substance in the environmental exposure assessment. It should also be noted that these values of log Pow represent that for aqueous pH at which the substance is not ionized. The components of this substance possess ionizable amino groups, which have estimated pKa values ranging from 14.2 to 14.5. Therefore, these substances will occur as partly- or fully-ionized species under the neutral pH conditions occurring in the environment, and will have hydrophobicity which is much less than indicated from log Pow.