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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:
April 13, 2018 - April 24, 2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
equivalent or similar to guideline
Guideline:
other: OECD 105 flask method
Deviations:
not applicable
Principles of method if other than guideline:
OECD 105 flask method
GLP compliance:
no
Type of method:
flask method
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
Key result
Type:
log Pow
Partition coefficient:
-1.6
Temp.:
20 °C
Remarks on result:
other: pH not determined

Preliminary visual estimation of the n-octanol solubility

Defined amounts of the test item were stirred with increasing volumes of n-octanol at room temperature and visually checked for any undissolved parts.

Table4: Results of the preliminary visual estimation of the n-octanol solubility

Amount of test item / mg

Added volume of n-octanol / mL

Total volume of n-octanol / mL

Stirring time

/ h

Appearance of mixture

126.6

2

2

1

dissolved

452.5

2

2

1

not dissolved

(not stirrable)

1

3

67

not dissolved

(stirrable)

According to this preliminary test the solubility of the test item in n-octanol was between 63 g/L and 151 g/L (without correction for the purity). Regarding the stirrability of the test runs a load of 150 g/L was used instead of the fivefold amount of the preliminary test.

Calculation of the partition coefficient log POW from the preliminary test

The partition coefficient POWmay be estimated from the saturation concentrations in n-octanol and water. The estimated partition coefficient was calculated with the water solubility data determined in project 20170181.04 (cS = 507 g/L) and the data obtained above. It was calculated to be: log POW < -0.5.

Due to the calculations the partition coefficient was estimated based on the ratio of the solubilities in water and octanol. The octanol solubility was determined using the flask method.The shake flask method was not applied due to the composition of the test item (salt content, mixture) and the HPLC method was not applicable due to the constitution of the test item (metal complex).

Determination of the solubility in n-octanol: Flask method

The individual saturation solubility of the test item in n-octanol was performed within this study. After that, the partition coefficient was estimated based on the ratio of the test item solubility in n-octanol and water. The flask method was performed as described above. The data for the evaluation are given in Table 5. The n-octanol solubility was calculated from the measured and unrounded concentration values and not from the rounded values given in Table 5.

 

Table5: n-Octanol solubility experiments of the test item

Experiment

24 h experiment

48 h experiment

72 h experiment

168 h experiment

blank

experiment (72 h)

Amount of test item / mg

3.2716

3.4502

3.3593

3.3069

--

Amount of octanol / mL

20

20

20

20

20

Stirring time at 30 °C / h

24

48

72

168

72

Dilution factor

500

500

500

500

500

Measured concentration / mg/L

26.53 / 26.51

22.10 / 22.06

13.55 / 13.48

11.19 / 11.19

-- / --

Mean concentration / mg/L

26.52

22.08

13.51

11.19

--

n-Octanol solubility / mg/L

13.3

11 0

6.8

5 6

--

The n-octanol solubilities showed a decreasing tendency. As a conservative approach the highest value was stated. The n-octanol solubility of the test item at 20 °C was determined to be 13.3g/L.

1.1.4.Calculation of the partition coefficient log POWfrom the individual solubilities

In theproject 20170181.04the water solubility of the test item at 20 °C was determined to be 507 g/L. Within this project the n-octanol solubility of the test item at 20 °C was determined to be 13.3 g/L.

The partition coefficient POWof the test item was determined to be: 

log POW= -1.6

Executive summary:

The partition coefficient (n-octanol/water) of the test item was estimated based on the ratio of the individual solubilities of the test item in water and n-octanol. The solubilities were determined according to the flask method. It was found to be without correction of the purity:

 

log POW = -1.6

Description of key information

The partition coefficient (n-octanol/water) of the test item was estimated based on the ratio of the individual solubilities of the test item in water and n-octanol. The solubilities were determined according to the flask method. It was found to be without correction of the purity:

 

log POW = -1.6

Key value for chemical safety assessment

Log Kow (Log Pow):
-1.6
at the temperature of:
20 °C

Additional information