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Partition coefficient

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Reference
Endpoint:
partition coefficient
Type of information:
calculation (if not (Q)SAR)
Adequacy of study:
key study
Study period:
14 Jun 2016
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to
Guideline:
other: Computational Approach in OECD Guideline 107 (EU A.8)
Principles of method if other than guideline:
According to the guidance of the ECHA a ratio calculation is an acceptable alternative for the determination of octanol/water Partition Coefficient of surfactants.
Citation from ''Guidance on information requirements and chemical safety assessment Chapter R.7a: Endpoint specific guidance'', 2014, R.7.1.8 Partition Coefficient, page 58:
This method enables partition coefficient to be calculated based on the ratio of the solubility of the material in octanol and water. For some substances (e.g. some surfactants and pigments), it is technically not feasible (or good practice) to measure an octanol-water partition coefficient by OECD 107, and other methods (OECD 117 and QSAR) may be unsuitable as they are based on extrapolations of measured values. For such substances it may be possible to obtain a ratio of the saturated water solubility (OECD 105) and saturated octanol solubility (no guideline currently available but based on the principles of OECD 105). The calculation method however has the drawback that it does not include the interaction between the water and solvent phase (i.e. a chemical with high Pow is rather ‘pushed out of the water’ than ‘pulled into octanol’). This explains the poor correlation typically observed between octanol solubility and Kow (Dearden, 1990, Sijm et al., 1999). The ratio was found somewhat more representative if one uses octanol/saturated water and water/saturated octanol.
GLP compliance:
no
Type of method:
other: calculated
Partition coefficient type:
octanol-water
Type:
log Pow
Partition coefficient:
> 0.23
Temp.:
20 °C
pH:
ca. 7
Remarks on result:
other: pH: cf. water solubility study

n-Octanol solubility of the test item: > 549 g/L at 20 °C (Report No. 15-17080/1-7 / 16-00805/1-7)

Water solubility of the test item: 322 g/L at 20 °C (Report No. 15-17080/1-8 / 16-00805/1-8)

Pow > 549/322 = 1.7; log Pow > 0.23.

 

Description of key information

log Pow > 0.23 at 20 °C, pH 7

Key value for chemical safety assessment

Log Kow (Log Pow):
0.23
at the temperature of:
20 °C

Additional information

The partition coefficient of the substance was determined using calculation method according to OECD 107 (EU A.8).