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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:
from 2018-11-05 to 2019-01-28
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 117 (Partition Coefficient (n-octanol / water), HPLC Method)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method A.8 (Partition Coefficient - HPLC Method)
Version / remarks:
European Commission Regulation (EC) No. 44012008 and No. 2016/266, A.24. Parlition coefficient n-octanol/water
Deviations:
no
GLP compliance:
no
Type of method:
HPLC method
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
Key result
Type:
log Pow
Partition coefficient:
5.7
Temp.:
20 °C
pH:
6.2
Details on results:
The log Pow was determined to be 5.7 at 20 °C.

Preliminary Visual Estimation of the Water Solubility

Increasing amounts of the test item were stirred with defined volumes of n-octanol at room temperature and visually checked for any undissolved particles.

Table 1. Results of the preliminary visual estimation of the n-octanol solubility

Added amount
of test item
in mg

Total amount
of test item

in mg

Added volume
of n-octanol
in mL

Total volume
of n-octanol
in mL

Stirring
time
in min

Appearance
of mixture

11.0

11.0

10

10

Without stirring

dissolved

96.3

107.3

--

10

10

dissolved

983

1090

--

10

15

dissolved

The solubility of the test item in n-octanol was > 109 g/L.

The water solubility of the test item was determined to be 1.04 mg/L. With the data obtained the partition coefficient was calculated as: log Pow > 5.0.

In addition the program KOWWIN (part of EpiSuite) was used to calculate the log Pow of the test item. The calculated value was 4.8.

Therefore, the partition coefficient n-octanol/water of the test item at room temperature was determined by the HPLC-method. 

HPLC-Method

Table 2. Determination of the Dead Time t0

Dead time
marker

tR in min
1st injection

tR in min
2nd injection

tR in min
mean

Formamide

1.04

1.04

1.04

 

Table 3. Calibration data 1st injection (* from OECD guideline 117, adopted 2004)

Calibration substance

tR in min

k

log k

log Pow*

2-Butanone

1.22

0.18

-0.76

0.3

Acetanilide

1.29

0.24

-0.63

1.0

Cinnamyl alcohol

1.52

0.46

-0.33

1.9

2,6-Dicholorobenzonitrile

1.92

0.84

-0.07

2.6

Allyl phenyl ether

2.72

1.62

0.21

2.9

Benzophenone

2.46

1.37

0.14

3.2

Cumene

4.96

3.76

0.58

3.7

Diphenyl ether

4.55

3.37

0.53

4.2

Fluoranthene

9.26

7.90

0.90

5.1

4,4' DDT

22.50

20.64

1.31

6.5

 

Regression: logPow = a + b * logk

Parameters: a = 2.620, b = 2.782, r2 = 0.9805

Table 4. log Pow of the test item – 2nd injection

tR in min

k

logk

log Pow

Test Item

14.63

13.07

1.12

5.7

 

Table 5. Calibration data 2nd injection (* from OECD guideline 117, adopted 2004)

Calibration substance

tR in min

k

log k

log Pow*

2-Butanone

1.22

0.17

-0.77

0.3

Acetanilide

1.29

0.24

-0.63

1.0

Cinnamyl alcohol

1.52

0.46

-0.33

1.9

2,6-Dicholorobenzonitrile

1.92

0.84

-0.07

2.6

Allyl phenyl ether

2.73

1.62

0.21

2.9

Benzophenone

2.47

1.37

0.17

3.2

Cumene

4.96

3.77

0.58

3.7

Diphenyl ether

4.55

3.38

0.53

4.2

Fluoranthene

9.29

7.93

0.90

5.1

4,4' DDT

22.58

20.71

1.32

6.5

 

Regression: logPow = a + b * logk

Parameters: a = 2.623, b = 2.773, r2 = 0.9808

Table 6. log Pow of the test item – 1st injection

tR in min

k

logk

log Pow

Test Item

14.66

13.10

1.12

5.7

 

Within two HPLC runs the partition coefficient log Pow of the test item was determined to be log Pow = 5.7.

Conclusions:
The log Pow of the test item was determined to be 5.7 at 20 °C.
Executive summary:

A study was conducted in accordance with OECD TG 117 and Regulation (EC) No 440/2008 method A.24 to determine the partition coefficient of the test substance using the HPLC method. In a preliminary test the solubility of the test item in n-octanol was determined to be >109 g/L. Based on this solubility and the solubility in water (1.04 mg/L), the log Pow was estimated to be >5.0, therefore, the HPLC method was used. The test item was dissolved in methanol by using an ultrasonic bath and diluted from 0.1 mL to 1 mL with the mobile phase. The dead time marker and the calibration substances each were dissolved in methanol and diluted from 0.1 mL to 1 mL (except for the calibration substance cinnamyl alcohol were the dilution was 0.05 mL to 1 mL with the mobile phase) with the mobile phase. All samples were injected as single solutions twice. Using the HPLC method for the main test, the value found for the partition coefficient n-octanol/water was found to be at 5.7.

Description of key information

The log Pow of the test item was determined to be 5.7 at 20 °C.

Key value for chemical safety assessment

Log Kow (Log Pow):
5.7
at the temperature of:
20 °C

Additional information

A study was conducted in accordance with OECD TG 117 and Regulation (EC) No 440/2008 method A.24 to determine the partition coefficient of the test substance using the HPLC method (reference 4.7-1). In a preliminary test the solubility of the test item in n-octanol was determined to be >109 g/L. Based on this solubility and the solubility in water (1.04 mg/L), the log Pow was estimated to be >5.0, therefore, the HPLC method was used. The test item was dissolved in methanol by using an ultrasonic bath and diluted from 0.1 mL to 1 mL with the mobile phase. The dead time marker and the calibration substances each were dissolved in methanol and diluted from 0.1 mL to 1 mL (except for the calibration substance cinnamyl alcohol were the dilution was 0.05 mL to 1 mL with the mobile phase) with the mobile phase. All samples were injected as single solutions twice. Using the HPLC method for the main test, the value found for the partition coefficient n-octanol/water was found to be at 5.7.