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Partition coefficient

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Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
2008-10-09 to 2008-12-19
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
unsuitable test system
Remarks:
It is not clear from the study report, if the volatility of the substance was taken into consideration, therefore, the reliability of the measured data is questionable
Qualifier:
according to
Guideline:
EU Method A.8 (Partition Coefficient)
Deviations:
not specified
Qualifier:
according to
Guideline:
OECD Guideline 117 (Partition Coefficient (n-octanol / water), HPLC Method)
Deviations:
not specified
GLP compliance:
no
Other quality assurance:
ISO/IEC 17025 (General requirements for the competence of testing and calibration laboratories)
Type of method:
HPLC method
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
Key result
Type:
log Pow
Partition coefficient:
>= 5.4 - <= 6.2
Temp.:
26 °C
pH:
7.35
Conclusions:
Log Kow (Pow) for Oxooel LS9 is measured to be 5.4 to 6.2 at 26 degrees C.
Executive summary:

As the test item is a mixture of several components, upper and lower limits of log Kow were determined using the HPLC method.

Log Kow (Pow) for Oxooel LS9 is measured to be 5.4 to 6.2 at 26 degrees C.

Endpoint:
partition coefficient
Type of information:
(Q)SAR
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification
Justification for type of information:
1. SOFTWARE
EpiSuite v4.11, US EPA, 2012

2. MODEL (incl. version number)
KOWWIN v1.68

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
see attachment (log Kow_QSAR justification.pdf)

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
- Defined endpoint: n-octanol-water partition coefficient
- Unambiguous algorithm: KOWWIN uses a "fragment constant" methodology to predict log P, known as an Atom/Fragment Contribution (AFC) method. Coefficients for individual fragments and groups were derived by multiple regression of 2447 reliably measured log P values.
Results of the two successive multiple regressions (first for atom/fragments and second for
correction factors) yield the following general equation for estimating log P of any organic compound:
log P = Σ(fini ) + Σ(cjnj ) + 0.229
(num = 2447, r2 = 0.982, std dev = 0.217, mean error = 0.159)

where Σ(fini ) is the summation of fi (the coefficient for each atom/fragment) times ni (the number of
times the atom/fragment occurs in the structure) and b is the linear equation constant; Σ(cjnj ) is the summation of cj (the coefficient for each correction factor) times nj (the number
of times the correction factor occurs (or is applied) in the molecule).

- Defined domain of applicability:
Currently there is no universally accepted definition of model domain. However, users may wish to
consider the possibility that log P estimates are less accurate for compounds outside the MW
range of the training set compounds, and/or that have more instances of a given fragment than the
maximum for all training set compounds. It is also possible that a compound may have a functional
group(s) or other structural features not represented in the training set, and for which no fragment
coefficient was developed. These points should be taken into consideration when interpreting
model results.

Training Set Molecular Weights:
Minimum MW: 18.02
Maximum MW: 719.92
Average MW: 199.98

Validation Molecular Weights:
Minimum MW: 27.03
Maximum MW: 991.15
Average MW: 258.98

- Appropriate measures of goodness-of-fit and robustness and predictivity:
The model has been tested on an external validation dataset of 10,946 compounds.
Total Validation Set Statistics:
number in dataset = 10946
correlation coef (r2) = 0.943
standard deviation = 0.479
absolute deviation = 0.356
avg Molecular Weight = 258.98

Validation Set Estimation Error:
within <= 0.20 - 39.6%
within <= 0.40 - 66.0%
within <= 0.50 - 75.6%
within <= 0.60 - 82.5%
within <= 0.80 - 91.6%
within <= 1.00 - 95.6%
within <= 1.20 - 97.7%
within <= 1.50 - 99.1%

5. APPLICABILITY DOMAIN
- Descriptor domain: The components of the substance are within the molecular weight range of the training set compounds, and all fragments are represented in the training set. Thus, it is concluded, that the substance is within the applicability domain.
- Similarity with analogues in the training set: several linear and branched alkanes and alkenes, which are considered to be similar, are present in the training set.

6. ADEQUACY OF THE RESULT
The QSAR prediction is valid and of good reliability. Thus, the result is adequate for chemical safety assessment.
Principles of method if other than guideline:
Estimation of the log Kow of the components by QSAR (EpiSuite v4.11, US EPA, 2012; KOWWIN v1.68)
GLP compliance:
no
Remarks:
not applicable for in silico study
Type of method:
calculation method (fragments)
Partition coefficient type:
octanol-water
Key result
Type:
log Pow
Partition coefficient:
4.17
Temp.:
25 °C
pH:
>= 0 - <= 14
Remarks on result:
other: weighted mean

for details see attachment

Conclusions:
The weighted mean log Kow of Oxooel LS9 was estimated to be 4.17 (EpiSuite v4.11, US EPA, 2012, KOWWIN v1.68).

Description of key information

The weighted mean log Kow of Oxooel LS9 was estimated to be 4.17 (EpiSuite v4.11, US EPA, 2012, KOWWIN v1.68).

Key value for chemical safety assessment

Log Kow (Log Pow):
4.17
at the temperature of:
25 °C

Additional information

As the test item is a mixture of several components, upper and lower limits of log Kow were determined using the HPLC method. Log Kow (Pow) for Oxooel LS9 was measured to be 5.4 to 6.2 at 26 degrees C.

However, it is not clear from the study report, if the volatility of the substance was taken into consideration, therefore, the reliability of the measured data is questionable. The contribution to the overall log Kow of the less volatile constituents, which are also more lipophilic, is probably overestimated in this experimental setting. In addition, no compound specific analytics were performed.

Thus, a calculation of the weighted mean log Kow based on QSAR (EpiSuite v4.11, US EPA, 2012, KOWWIN v1.68) was performed, which is used as key value for chemical safety assessment: The weighted mean log Kow of Oxooel LS9 was estimated to be 4.17.