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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:
15 May - 23 Jun 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reason / purpose for cross-reference:
reference to other study
Qualifier:
according to guideline
Guideline:
other: Regulation EC No. 440/2008 Part A., Method A.6. Water Solubility
Qualifier:
according to guideline
Guideline:
other: OECD Test Guideline 105 Water Solubility
Version / remarks:
1995
Qualifier:
according to guideline
Guideline:
other: ECHA Guidance on Information Requirements and Chemical Safety Assessment, Chapter R.7a: Endpoint specific guidance
Version / remarks:
Version 6.0, 2017
Principles of method if other than guideline:
Due to the fact that the test item is a surface active substance, the standard methods for the determination of the partition coefficient are not recommended according to ECHA Guidance on Information Requirements and Chemical Safety Assessment, Chapter R.7a: Endpoint specific guidance (Version 6.0, 2017). The partition coefficient of the test item was calculated by using the octanol solubility and the water solubility.
GLP compliance:
not specified
Type of method:
estimation method (solubility ratio)
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
Key result
Type:
log Pow
Partition coefficient:
< -2.7
Temp.:
20 °C
pH:
>= 6.17 - <= 6.38
Remarks on result:
other: pH measured only for octanol solubility.

Preliminary Test

The preliminary test at room temperature showed, that the octanol solubility of the test item was between 0.9 g/L and 1.3 g/L. The observations of the preliminary test are summarized in the following table.

Amount of test item

[g]

Total volume of added octanol

[mL]

Stirring time

[min]

Remark

0.35

10

30

not dissolved

40

55

not dissolved

90

40

not dissolved

0.13

50

85

not dissolved

100

30

not dissolved

150

Over night

dissolved

 

The solubility of the test item in octanol at room temperature was estimated to be > 0.9 g/L and < 1.3 g/L. Therefore, the flask method was performed.

 

Main Test (flask method)

For the main test three flasks were prepared with an amount of test item and octanol, and one flask only with octanol. After stirring and centrifugation the organic phases were measured by means of HPLC. The solution of each flask has been measured twice. The results of these measurements are shown in the following table. The values represented in the table are rounded values. The calculation was carried out with the original not rounded values.

 

Flask

1a

2a

3a

4a

measured value [g/L]

3.91 / 3.95

4.45 / 4.40

4.63 / 4.45

0 / 0

octanol solubility [g/L]

3.91 / 3.95

4.45 / 4.40

4.63 / 4.45

0 / 0

average octanol solubility [g/L]

3.93

4.42

4.54

0

mean value of the octanol solubility [g/L]

4.30

 

0

standard deviation [g/L]

0.32

--

relative standard deviation [%]

7.5

--

 

To verify the accuracy of the analytical method fresh prepared standard solutions (prepared with the test item) were measured in between the samples of the flask method. The results of these measurements are shown in the following table.

 

Standard solution

(nominal value [g/L])

Measured value [g/L]

Repeatability [%]

Standard-1 (4.58)

4.70

102.4

4.67

102.0

4.75

103.7

4.72

103.1

Standard-2 (5.25)

5.32

101.3

5.30

101.0

5.31

101.1

5.37

102.3

 

The recovery rate of the measured standard solutions was in the range from 101.0 % to 103.7 %, which shows a good accuracy of the analytical method

 

Partition Coefficient

The partition coefficient is calculated with the determined octanol solubility of this study and the water solubility of study CSL-17-0689.02 (see section 4.8) by using following equation:

POW = C1-octanol / Cwater= 4. 30 g/L / >2054 g/L

 

log POW = < -2.7

 

 

Final Results

Octanol Solubility

According to OECD Test Guideline 105 (1995) and Regulation EC No. 440/2008 Method A.6. the octanol solubility at 20 °C of the test item was determined to be:

cS = 4.30 g/L

RSD = 7.5 %

 

Partition Coefficient

The calculated partition coefficient at 20 °C of the test item using the determined octanol solubility of this study and the water solubility of study CSL-17-0689.02 was determined to be:

log Pow < -2.7

Description of key information

Log Kow: < -2.7 at 20 °C (EU Method A.8 - Appendix I, estimation method)

Key value for chemical safety assessment

Additional information

Due to the fact that the test item is a surface active substance, the standard methods for the determination of the partition coefficient are not recommended according to ECHA Guidance on Information Requirements and Chemical Safety Assessment, Chapter R.7a: Endpoint specific guidance (Version 6.0, 2017).

The partition coefficient was estimated from the n-octanol solubility (4.30 g/L, pH 6.17-6.38; OECD Guideline 105, adapted) and the water solubility (>2054 g/L; OECD Guideline 105) of the test substance.