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Physical & Chemical properties

Partition coefficient

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Reference
Endpoint:
partition coefficient
Type of information:
experimental study
Remarks:
Migrated phrase: estimated by calculation
Adequacy of study:
key study
Study period:
07 Oct - 23 oct 2015
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 107 (Partition Coefficient (n-octanol / water), Shake Flask Method)
Version / remarks:
adopted in 2008
Qualifier:
according to guideline
Guideline:
EU Method A.8 (Partition Coefficient - Shake Flask Method)
GLP compliance:
no
Type of method:
flask method
Partition coefficient type:
octanol-water
Specific details on test material used for the study:
Storage conditions: ambient temperature (10 – 30 °C)
Analytical method:
high-performance liquid chromatography
Type:
log Pow
Partition coefficient:
< -1.7
Temp.:
23 °C
pH:
ca. 7

Results
Table 1 - Preliminary visual estimation of n-octanol solubility

Added test item amount [g]

Total test item amount [g]

Added n-octanol volume [mL]

Total n-octanol volume [mL]

Stirring time [min]

Appearance of mixture

0.0063

0.0063

10

10

140

Not dissolved

--

0.0063

90

100

1015

Few small particles

0.0171

0.0234

--

100

430

 

Results showed that the n-octanol solubility of the test item is < 0.63 g/L (without correction for the purity).

 

Calculation of the Partition Coefficient log POW
Using the water solubility determined in the study report 20150266.04 (cS> 0.88 g/L) and the preliminary results, it was found that log POW< -0.2

Due to the calculation results, the shake flask method was performed.
The calculated value from KOWWIN was 1.2.

 

Shake Flask Method
The test item is a zwitterionic substance, thus the method had to be carried out at pH 7 (or the isoelectric point). The given values of the concentrations in the aqueous and n-octanol phases are mean values of two measurements.

Table 2 – Results and test conditions of the shake flask method

Experiment

1A

1B

2A

2B

3A

3B

Test item amount [mg]

22.3

Stock solution concentration [mg/L]

223

Added stock solution volume [mL]

10

Added n-octanol volume [mL]

0

0

10

10

30

30

Added buffer volume [mL]

20

pH of aqueous phase at 23 °C

7.0

Aqueous phase measured concentration [mg/L]

2.23
2.22

2.22
2.21

2.23
2.23

2.24
2.24

2.20
2.20

2.21
2.20

Aqueous phase mean concentration [mg/L]*

111.1

110.8

111.3

111.8

110.2

110.3

n-octanol phase measured concentration [mg/L]

< 0.06
< 0.06

n-octanol phase mean concentration [mg/L]*

< 2.28

*for the mean concentration, the sample preparation (dilution) is taken into account

The following partition coefficients were calculated from the measured and unrounded concentration values and not from the rounded values given in Table 2 .

Table 3 – Partition coefficients of the shake flask method at pH 7

Experiment

POW

lop POW

Average log POW

1A

0.025

< -1.69

< -1.69

1B

0.0206

2A

0.0205

< -1.69

2B

0.0204

3A

0.0207

< -1.68

< -1.68

3B

0.0207

< -1.69

Mean value (1A to 3B)

< -1.7

Standard deviation

0.002

 

The six determined log POW values are within a range of ± 0.3 units as requested by the guideline.

Conclusion: The partition coefficient at pH 7 and 23 °C of the test item was found to be:

log POW< -1.7

Description of key information

log POW < -1.7 at pH 7 and 23 °C (OECD 107, Shake Flask Method)

Key value for chemical safety assessment

Additional information

The partition coefficient (n-octanol/water) was firstly estimated based on the ratio of the individual solubilities of the test item in water and n-octanol. The exact partition coefficient was determined according to the flask method described in the european Commission Regulation (EC) No. 440/2008, A.8. and in the OECD Guideline 107.

Based on calculations for logD performed using the model SPARC v4.6, the partition coefficient (log Pow) is equal to the log D at pH 7.