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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:
February 01, 2018 - February 09, 2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
equivalent or similar to guideline
Guideline:
other: OECD 105
Deviations:
not applicable
Principles of method if other than guideline:
OECD 105
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:
-0.22
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

13

10

10

18

dissolved

100.3

2.5

2.5

1

not dissolved

7.5

10

1

not dissolved

According to this preliminary test the solubility of the test item in n-octanol was between 1.3 g/L and 10.0 g/L (without correction for the purity).

Calculation of the partition coefficient log POW from 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 PS20170183.04 (cS = 81 g/L) and the data obtained above. It was calculated to be: log POW < -0.9. Due to the calculations the shake flask method or the HPLC method should be suitable for the determination of the partition coefficient. Nevertheless, the shake flask method applies only to essentially pure substances (content of Acid Yellow 232 = 68.8 % (w/w)) and the HPLC method is not recommended for metal complexes like the present test item. Therefore, the partition coefficient of the present test item was estimated based on the ratio of the solubilities in water and octanol. The octanol solubility was determined using the flask method.

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 Table5. The n-octanol solubility was calculated from the measured and unrounded concentration values and not from the rounded values given in Table5.

Table5: 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 / g

1.009

1.041

1.003

--

Amount of octanol / mL

20

20

20

20

Stirring time at 30 °C / h

24

48

72

72

Dilution factor

1000

1000

1000

1000

Measured concentration / mg/L

48.6 / 48.6

48.3 / 48.3

48.1 / 48.2

-- / --

Mean concentration / mg/L

48.6

48.3

48.2

--

n-Octanol solubility / g/L

48.6

48.3

48.2

--

The n-octanol solubility of the test item at 20 °C was determined to be48.4g/L (± 0.2 g/L), without correction of the purity.

 

Calculation of the partition coefficient log POW from the individual solubilities

In theproject 20170183.04 the water solubility of the test item at 20 °C was determined to be 81 g/L. Within this project the n-octanol solubility of the test item at 20 °C was determined to be 48.4 g/L.

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

log POW=  - 0.22

Executive summary:

The partition coefficient (n-octanol/water) of the test item Acid Yellow 232 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 large content of salt in the sample and thecontent of only 68.8 % (w/w) of the main constituent. It was found to be (without correction of the purity):

log POW =  - 0.22

Description of key information

The partition coefficient (n-octanol/water) of the test item Acid Yellow 232 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 large content of salt in the sample and thecontent of only 68.8 % (w/w) of the main constituent. It was found to be (without correction of the purity):

log POW =  - 0.22

Key value for chemical safety assessment

Additional information