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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:
May 04, 2018 to May 14, 2018
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:
The octanol solubility was determined using the flask method (OECD105). The shake flask method and the HPLC method were not applicable due to the low log POW.
Deviations:
no
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:
>= -2.1
Temp.:
20 °C
Remarks on result:
other: pH not determined

Individual Results

 Preliminary visual estimation of the n-octanol solubility

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

Table 3: 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

3.3

5

5

~2.5

not dissolved

20

25

~2.5

not dissolved

80

105

~65

not dissolved

According to this preliminary test the solubility of the test item in n-octanol was below 32 mg/L.

Calculation of the partition coefficient log POWfrom the preliminary test

The partition coefficient POW may 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 PS20170192-4 (cS = 12.7 g/L) and the data obtained above. It was calculated to be: log POW < -2.6.

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.

 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 4. The n-octanol solubility was calculated from the measured and unrounded concentration values and not from the rounded values given in Table 4. 

Table 4: n-Octanol solubility experiments of the test item

Experiment

24 h experiment

48 h experiment

72 h experiment

72 h experiment[1]

blank

experiment (72 h)

Amount of test item / mg

26.7

26.0

27.1

30.8

--

Amount of octanol / mL

50

50

50

50

50

Stirring time at 30 °C / h

24

48

72

72

(+ 96 h at 20 °C)

72

Dilution factor

40

40

40

40

40

Measured concentration / mg/L

0.474 / 0.473

0.560 / 0.560

0.580 / 0.578

1.619 / 1.621

- / -

Mean concentration / mg/L

0.473

0.560

0.579

1.620

-

n-Octanol solubility (main peak) / mg/L

18.9

22.4

23.2

64.8

-

n-Octanol solubility (corrected by the content) / mg/L

32

38

39

109

-

The solubility of the test item in n-octanol increased with the stirring time. For this reason the highest value was taken as final result. The n-octanol solubility of the test item at 20 °C was determined to be

≥ 109 mg/L (corrected by the content).

Calculation of the partition coefficient log POW from the individual solubilities

In the project PS20170192-4 the water solubility of the test item at 20 °C was determined to be 12.7 g/L. Within this project the n-octanol solubility of the test item at 20 °C was determined to be ≥ 109 mg/L.

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

log POW ≥ -2.1


[1] The stirring time at 20 °C was prolonged from 24 h to 96 h.

Executive summary:

The partition coefficient (n-octanol/water) of the test item Reactive Red 123 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 ≥ -2.1

 

Description of key information

The partition coefficient (n-octanol/water) of the test item Reactive Red 123 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 ≥ -2.1

 

Key value for chemical safety assessment

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