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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:
25 July 2008 to 17 November 2008
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study conducted to GLP in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results.
Reference:
Composition 0
Qualifier:
according to
Guideline:
EU Method A.8 (Partition Coefficient)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of method:
shake-flask method to: flask method
Partition coefficient type:
octanol-water
Test material information:
Composition 1
Analytical method:
high-performance liquid chromatography
Type:
Pow
Partition coefficient:
0.065
Temp.:
21.1 °C
pH:
7
Remarks on result:
other: Mean value
Type:
log Pow
Partition coefficient:
-1.19
Temp.:
21.1
pH:
7
Remarks on result:
other: Mean value
Details on results:
PRELIMINARY TEST
- Approximate solubility in n-octanol: <5.00 x 10^-3 g/L
- Approximate solubility in water: >48.76 g/L
- Approximate Pow: 1.03 x 10^-4
- Log10 Pow: -3.99

VALIDATION
The linearity of the detector response with respect to concentration was assessed over the nominal concentration range of 0 to 250 mg/L for the aqueous phase and 0 to 100 mg/L for the organic phase. This was satisfactory with correlation coefficients of 0.998 being obtained for both aqueous and organic phases.

Table 2: Total weights (mg) and analysed concentration (mg/L) of the respective phases

Sample Number

Volume of water saturated n-octanol (mL)

Volume of stock solution (mL)

Total Weight (mg)*

Organic Phase

Aqueous Phase

pH

Analysed Concentration (mg/L)

Weight (mg)

Analysed Concentration (mg/L)

Weight (mg)**

1

360

18

22.3

38.7

13.9

776

14.0

1.6

2

360

18

22.3

34.9

12.6

714

12.9

1.6

3

300

30

37.2

56.2

16.9

941

28.2

1.7

4

300

30

37.2

62.9

18.9

911

27.3

1.7

5

260

52

64.4

62.3

16.2

1.03 x 10^3

53.5

1.7

6

260

52

64.4

104

27.0

1.05 x 10^3

54.4

1.7

* = from analysis of the stock solution

** = from analysis of the respective phase

 

- pH of n-octanol saturated water: 1.1

- pH of stock solution: 1.6

- Temperature: 22.1 ± 0.5 °C

 

Table 3: The partition coefficient determined for each sample

Sample Number

n-Octanol / Water Volume Ratio

Partition Coefficient

Log10 Pow

Mean Partition Coefficient

1

20:1

4.99 x 10-2

-1.30

4.94 x 10-2

2

4.89 x 10-2

-1.31

3

10:1

5.97 x 10-2

-1.22

6.44 x 10-2

4

6.91 x 10-2

-1.16

5

5:1

6.06 x 10-2

-1.22

7.99 x 10-2

6

9.93 x 10-2

-1.00

 

- Mean Pow: 6.46 x 10^-02

- log10 Pow: -1.19

- Pow standard deviation: 1.86 x 10^-02

Conclusions:
Under the conditions of the study, the partition coefficient of the test material has been determined to be 0.0646, log10 Pow -1.19 at 21.1 ± 0.5 °C. The estimated partition coefficient of the test material at pH 7 was calculated to be 0.0000191 log10 Pow -4.72 at pH 7.
Executive summary:

The partition coefficient of the test material was determined in a study which was conducted under GLP conditions and in accordance with the standardised guideline EU Method A.8 according to the flask method using HPLC analysis.

Under the conditions of the study, the partition coefficient of the test material has been determined to be 0.0646, log10 Pow -1.19 at 21.1 ± 0.5 °C. The estimated partition coefficient of the test material at pH 7 was calculated to be 0.0000191 log10 Pow -4.72 at pH 7.

Description of key information

Pow = -1.19 (log Pow = 0.0646), pH 7, EU Method, A.8., shake flask method, Buterl & O'Connor (2008)

Key value for chemical safety assessment

Log Kow (Log Pow):
0.065
at the temperature of:
21.1 °C

Additional information

The partition coefficient of the test material was determined in a study which was conducted under GLP conditions and in accordance with the standardised guideline EU Method A.8. The shake flask method was used to determine the partition coefficient of the test material with the standards and samples being analysed by LC-MS. The study was assigned a reliability score of 1 in line with the principles for assessing data quality as defined by Klimisch (1997).

A preliminary assessment of the partition coefficient was made based on the approximate solubilities of the test material in n-octanol and water. For the definitive test, 6 partitions were performed; in each test, the combined volume of both phases occupied not less than 90 % of the total volume of the test vessel. The shaking was performed by inversion of the flasks through approximately 180 ° over a five minute period. After separation, aliquots of both phases were centrifuged at 13500 rpm for 15 minutes and the supernatant taken for analysis.

Under the conditions of the study, the partition coefficient of the test material has been determined to be 0.0646, log10 Pow -1.19 at 21.1 ± 0.5 °C. The estimated partition coefficient of the test material at pH 7 was calculated to be 0.0000191 log10 Pow -4.72 at pH 7.