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EC number: 269-214-1 | CAS number: 68201-37-6
Partition coefficient
Administrative data
Link to relevant study record(s)
Description of key information
log Pow > 4
Key value for chemical safety assessment
Additional information
The value for partition coefficient log Pow of UVCB substance is based on a weight of evidence using experimental and QSAR results for the components of the substance. Due to the complex nature of the UVCB substance not all components of the substance are known. For the evaluation of the influence of the dimerisation and branching, the hypothetical structures were examined with use of QSAR model (KOWWIN v1.68).
The experimental literature partition coefficient log Pow for monomers of C16-18 fatty acids are all above 6: log Pow=8.23 for octadecanoic acid, 7.17 for palmitic acid and 7.45 for heptadecanoic acid. The partition coefficient of the substance increases with the increase of number the C chain incrementally. Log Pow of the dimer of C18 fatty acids is then expected to be much higher than log Pow of monomers. It is also proven by QSAR prediction for example dimer structure (log Pow = 14.81). The branching does not affect the log Pow substantially and it was calculated by KOWWIN v1.68 for an example structure of C16 acid to be 6.45.
The log Pow was also experimentally determined (HPLC method, OECD 117) with Octadecanoic Acid, branched and linear (CAS 68201-37-6). In unbuffered media, a partition coefficient range of 4.0 to 5.9 was determined. The pH of this sample was measured as ca 5-6.
In media adjusted to pH 2, a partition coefficient range of 5.6 to >6 (6.1) was determined. The results from this testing need to be viewed with caution as the method only covers materials with partition coefficient values in the range 0 to 6. Some components within the mixtures had estimated values out of this range.
All available results show that the log Pow of Octadecanoic Acid, branched and linear (CAS 68201-37-6) is high and well above 4. Therefore log Pow >4 cut-off value is accepted for the chemical safety assessment.
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