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Physical & Chemical properties

Partition coefficient

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Reference
Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP guideline study without deviation
Qualifier:
according to guideline
Guideline:
OECD Guideline 123 (Partition Coefficient (1-Octanol / Water), Slow-Stirring Method)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of method:
other: slow-stiirring method
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
Type:
log Pow
Partition coefficient:
4.56
Temp.:
25 °C
pH:
7.8 - 8
Remarks on result:
other: The measured pH of the aqueous phases were between 7.83 and 7.96 at 21 °C.

The results in the two phases at each time are given in the following table:

 

Vessel Number and

Sampling time

Concentration in the aqueous phase (mg/L)

Concentration in the 1-octanol phase (mg/L)

Pow Ratio

Log Pow

13-004 1Za T = 136H

0.56

20400

36428.6

4.561

13-004 1Zb T = 136H

0.58

20800

35862.1

4.555

13-004 1Zc T = 136H

0.58

20850

35948.3

4.556

13-004 1Za T = 160H

0.56

20200

36071.4

4.557

13-004 1Zb T = 160H

0.58

20600

35517.2

4.550

13-004 1Zc T = 160H

0.56

20500

36607.1

4.564

13-004 1Za T = 166H

0.56

20100

35892.9

4.555

13-004 1Zb T = 166H

0.58

20700

35689.7

4.553

13-004 1Zc T = 166H

0.56

20500

36607.1

4.564

13-004 1Za T = 184H

0.60

21550

35916.7

4.555

13-004 1Zb T = 184H

0.58

20900

36034.5

4.557

13-004 1Zc T = 184H

0.56

19800

35357.1

4.548

13-004 1Za T = 190H

0.56

19900

35535.7

4.551

13-004 1Zb T = 190H

0.58

20900

36034.5

4.557

13-004 1Zc T = 190H

0.60

21450

35750.0

4.553

 

 

The average value of log Pow of the different vessel units is calculated as the average of the results of the individual experimental units weighed with their respective variances.The results are shown in the following tables.

 

Vessel 1Za

Mean value 1Za

Variance 1Za

Vessel 1Zb

Mean value 1Zb

Variance 1Zb

Vessel 1Zc

Mean value 1Zc

Variance 1Zc

4.561

4.557

4.555

4.555

4.551

4.556

0.000011

4.555

4.550

4.553

4.557

4.557

4.554

0.000007

4.556

4.564

4.564

4.548

4.553

4.557

0.000039

 

Mean/vessel

Variance

Weighed average

4.556

4.554

4.557

0.000011

0.000007

4.557000

4.557

 

Executive summary:

The partition coefficient n-octanol/water (Kow) of tert-amyl peroxy-2-ethylhexanoate was estimated using the slow-stirring method. The Kow test was performed in accordance with the OECD 123 guideline. It was shown that the weighted average value of the 1-octanol/water partition coefficient log10 Pow of the substance is equal to 4.556 ± 0.001 at 25 ± 1 °C.

The result issued from the statistical calculations can be given as 4.56.

Description of key information

OECD 123, GLP, slow-stirr method, key study, validity 1:
Log Kow = 4.56 at 25°C

Key value for chemical safety assessment

Log Kow (Log Pow):
4.56
at the temperature of:
25 °C

Additional information

A first study was performed according to OECD Guideline 117 with GLP statement. However, the HPLC method could overestimate the Kow for certain structures: there is some evidence that those containing oxygen may be susceptible to the formation of hydrogen bond within the column that could slow down molecules. That's why the partition coefficient n-octanol/water (Kow) of tert-amyl peroxy-2-ethylhexanoate was estimated using the slow-stirring method in accordance with the OECD 123 guideline, which appears to be more suitable. With this method, it was shown that the weighted average value of the 1-octanol/water partition coefficient log10 Pow of the substance is equal to 4.556 ± 0.001 at 25 ± 1 °C.The result issued from the statistical calculations can be given as 4.56.