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Partition coefficient

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Reference
Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
key study
Study period:
27 September - 08 October 2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
equivalent or similar to
Guideline:
other: OECD Guideline 105 (“Water Solubility”)
Version / remarks:
adopted July 27, 1995
Deviations:
not applicable
Principles of method if other than guideline:
The determination of the log Pow using the respective OECD guideline methods was technically not feasible due to the intrinsic properties of the test item:
- The test item is a UVCB and neither the flask-shake (OECD TG 107) nor the slow-stir method (OECD TG 123) for the determination of the log Pow are applicable to complex mixtures.
- The test item cannot be chromatographed under the conditions described in the HPLC-method (OECD Guideline 117) since it is insoluble in the solvents used for the reverse phase HPLC.
- The test item has no defined chemical structure; therefore the calculation of the log Pow with a QSAR tool is not possible.
Hence, the log Pow has to be estimated based on individual solubility of the test item in water and n-octanol
GLP compliance:
yes (incl. certificate)
Type of method:
estimation method (solubility ratio)
Partition coefficient type:
octanol-water
Analytical method:
photometric method
other: observation of precipitated substance particles in n-octanol
Key result
Type:
Pow
Partition coefficient:
< 0.6
Temp.:
20 °C
pH:
>= 4.42 - <= 4.62
Remarks on result:
other: pH as determined in water solubility study
Key result
Type:
log Pow
Partition coefficient:
< -0.2
Temp.:
20 °C
pH:
>= 4.42 - <= 4.62
Remarks on result:
other: pH as determined in water solubility study
Details on results:
Undissolved particles were still observed in the test item / n-octanol mixture at the concentration ca.1 mg test item / 500 mL n-octanol after 24 hours.
Based on this observation, the solubility of the test item in n-octanol is less than 2.16 mg/L.
The solubility of the test item in water is 3.37 mg/L as determined in a separate GLP study (see "water solubility").
The Pow value of the test item was calculated using the following equation:
Pow: So/Sw

where:
So solubility in n-octanol
Sw solubility in water

Based on the individual solubility of test item in water and n-octanol, the estimated
Pow: < 0.6, the estimated log Pow: <-0.2.
Conclusions:
Based on the individual solubility of test item in water and n-octanol, the estimated Pow: < 0.6, the estimated log Pow: <-0.2.
Executive summary:

The test item is a UVCB substance with an unknown and highly complex composition. Therefore, neither the estimation of the log Pow by QSAR nor its determination with OECD Guideline 107 (shake flask method) is feasible. For the HPLC-method (OECD Guideline 117), which is the recommended method for mixtures, the structural formula of the test item should be known and the test item must be soluble in the mobile phase in sufficient concentration. The test item does not meet those requirements since its structural formula is not known and it is insoluble in the mobile phases applicable for this method. Consequently, the HPLC-method (OECD Guideline 117) is also not feasible and the log Pow of the test item can only be estimated from its individual solubility in water and in n-octanol.

Considering the water solubility and the n-octanol solubility a Pow of <0.6 and log Pow of <-0.2 have been estimated.

Description of key information

Based on the individual solubility of test item in water and n-octanol, the estimated  Pow: < 0.6, the estimated log Pow: <-0.2.

Key value for chemical safety assessment

Log Kow (Log Pow):
-0.2
at the temperature of:
20 °C

Additional information

The test item is a UVCB substance with an unknown and highly complex composition. Therefore, neither the estimation of the log Pow by QSAR nor its determination with OECD Guideline 107 (shake flask method) is feasible. For the HPLC-method (OECD Guideline 117), which is the recommended method for mixtures, the structural formula of the test item should be known and the test item must be soluble in the mobile phase in sufficient concentration. The test item does not meet those requirements since its structural formula is not known and it is insoluble in the mobile phases applicable for this method. Consequently, the HPLC-method (OECD Guideline 117) is also not feasible and the log Pow of the test item can only be estimated from its individual solubility in water and in n-octanol.

Considering the water solubility and the n-octanol solubility aPow of <0.6 and log Pow of <-0.2 have been estimated.