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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:
October 12, 2018 - October 19, 2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 107 (Partition Coefficient (n-octanol / water), Shake Flask Method)
Deviations:
not applicable
Principles of method if other than guideline:
OECD 105
GLP compliance:
yes (incl. certificate)
Type of method:
flask method
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
Key result
Type:
log Pow
Partition coefficient:
<= -5.7
Temp.:
20 °C
Remarks on result:
other: calculated based on maximum solubility in each solvent
Remarks:
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 particles.

Table: 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

5.1

10

10

1

not dissolved

90

100

~64

not dissolved

According to this preliminary test the solubility of the test item in n-octanol was below 51 mg/L (without correction for the purity).

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 PS20180303-4 (preliminary test: cS > 182 g/L) and the data obtained above. It was calculated to be: log POW < -3.6.

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 and the HPLC method were not applicable due to the low log POW and as the test item is surface-active (see report PS20180303-3).

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 7. The n-octanol solubility was calculated from the measured and unrounded concentration values and not from the rounded values given in Table 7.


 Table: n-Octanol solubility experiments of the test item

Experiment

24 h experiment

48 h experiment

72 h experiment

blank

experiment (72 h)

Amount of test item / mg

5.5

5.5

5.5

--

Amount of octanol / mL

20

20

20

20

Stirring time at 30 °C / h

24

48

72

72

Dilution factor

1.25

1.25

1.25

1.25

Results for main constituent 1

Measured concentration / mg/L

<0.205 / <0.205

<0.205 / <0.205

<0.205 / <0.205

-- / --

Mean concentration / mg/L

<0.205

<0.205

<0.205

--

n-Octanol solubility / mg/L

<0.164

<0.164

<0.164

--

Results for main constituent 2

Measured concentration / mg/L

<0.124 / <0.124

<0.124 / <0.124

<0.124 / <0.124

-- / --

Mean concentration / mg/L

<0.124

<0.124

<0.124

--

n-Octanol solubility / mg/L

<0.099

<0.099

<0.099

--

The n-octanol solubility of the test item at 20 °C was determined to be

< 0.16 mg/L for main constituent 1

< 0.10 mg/L for main constituent 2

resulting in a total n-octanol solubility of

< 0.26 mg/L main constituent 1 & 2

Calculation of the partition coefficient log POW from the individual solubilities

In the project PS20180303-4 the water solubility of the test item at 20 °C was determined to be

81.1 g/L for main constituent 1 and

47.4 g/L for main constituent 2,

resulting in a total water solubility of

128.5 g/L main constituent 1 & 2.

Within this project the n-octanol solubility of the test item at 20 °C was determined to be

< 0.16 mg/L for main constituent 1

< 0.10 mg/L for main constituent 2

resulting in a total n-octanol solubility of

< 0.26 mg/L main constituent 1 & 2


 

The partition coefficient POW of the test item was determined to be:          

For main constituent 1:        log POW<  -5.7

For main constituent 2:        log POW<  -5.7

For main constituent 1&2:    log POW<  -5.7

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.The shake flask method and the HPLC method were not applicable due to the low log POW.

It was found to be:

log POW < -5.7

for main constituent 1, main constituent 2, and main constituent 1 & 2.

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.The shake flask method and the HPLC method were not applicable due to the low log POW.

It was found to be:

log POW < -5.7

for main constituent 1, main constituent 2, and main constituent 1 & 2.

Key value for chemical safety assessment

Additional information