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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:
December 08, 2017 to December 19, 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 107 (Partition Coefficient (n-octanol / water), Shake Flask Method)
Version / remarks:
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 applicable due to the large salt content of the sample.
Deviations:
no
Qualifier:
according to
Guideline:
EU Method A.8 (Partition Coefficient - Shake Flask Method)
Version / remarks:
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 applicable due to the large salt content of the sample.
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:
>= 0.1
Temp.:
20 °C
Remarks on result:
other: pH not determined

Results

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

103.4

5

5

~ 2

not dissolved

5

10

~1.5

not dissolved

40

50

~ 1.5

not dissolved

50

100

~65

not dissolved

According to this preliminary test the solubility of the test item in n-octanol was below 1.034 g/L (without correction for the purity).

Calculation of the log POW from the preliminary test

The estimated partition coefficient was calculated with the water solubility data determined in project 20170182.04 (cS = 0.055 g/L) and the data obtained above. It was calculated to be:

log POW < 1.3.

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 applicable due to the large salt content of the sample.

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

168 h experiment

blank

experiment (72 h)

Amount of test item / mg

275.6

293.3

251.3

251.7

--

Amount of octanol / mL

50

50

50

50

50

Stirring time at 30 °C / h

24

48

72

168

72

Dilution factor

40

40

40

40

40

Measured concentration / mg/L

1.88 / 1.90

1.01 / 1.02

0.99 / 1.01

0.96 / 0.96

-- / --

Mean concentration / mg/L

1.89

1.01

1.00

0.96

--

n-Octanol solubility / g/L

0.076

0.041

0.040

0.038

--

The solubility experiments showed a decreasing amount of the test item at increasing stirring time. This may result from instability of the test item in n-octanol. Therefore, as a conservative approach the highest measured concentration was taken into account. Hence, the n-octanol solubility of the test item at 20 °C was determined to be≥ 0.076g/L without correction of the purity.

 

Calculation of the partition coefficient log POWfrom the individual solubilities

In theproject 20180182.04 the water solubility of the test item at 20 °C was determined to be 0.055 g/L (± 0.006 g/L). Within this project the n-octanol solubility of the test item at 20 °C was determined to be ≥ 0.076 g/L without correction of the purity.

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

log POW 0.1

Executive summary:

The partition coefficient (n-octanol/water) of the test itemAcid Red 299 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 HPLC and shake flask method were not applicable due to the large salt content of the sample.

Without correction of the purity the partition coefficient was found to be:

 

log POW 0.1

Description of key information

The partition coefficient (n-octanol/water) of the test item Acid Red 299 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 HPLC and shake flask method were not applicable due to the large salt content of the sample.

Without correction of the puritythe partition coefficient was found to be:

 

log POW 0.1

Key value for chemical safety assessment

at the temperature of:
20 °C

Additional information