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Water solubility

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Reference
Endpoint:
water solubility
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From September 22, 2004 to October 15, 2004
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 105 (Water Solubility)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method A.6 (Water Solubility)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of method:
flask method
Key result
Water solubility:
475.3 g/L
Conc. based on:
test mat.
Incubation duration:
>= 24 - <= 72 h
Temp.:
20 °C
pH:
ca. 5.4
Remarks on result:
other: SD: 32.4 g/L

Preliminary Visual Estimation of the Water Solubility

Increasing water amounts were added stepwise to about 100 mg of the test substance.

Table: Appearance of the test mixtures

Amount of the test substance (mg)

Total volume (mL)

Appearance of mixture

96.55

0.1

Undissolved

0.5

Dissolved

 

The preliminary visual experiments showed that the water solubility of the test substance was between 190 and 970 g/L.Therefore, the water solubility had to be determined by the "flask-method".

 

Due to the fact that it was not possible to stir about five times of the visual estimated quantity with distilled water, only 20 to 23 g of the homogenised test substance were stirred with 20 mL distilled water.

 

Table: results of the first main test

 

Experiment

Amount of the test substance (g)

Distilled water (mL)

Dilution with water

Measured concentration (HPLC) in g/L

A

23.26

20

0.061 g - 99.59 g

540

B

22.27

20

0.065 g - 99.69 g

521

C

20.08

20

0.058 g - 99.72 g

493

 

It was not possible to filter the solutions in experiments A to C. The solutions appeared as highly viscous. Only experiment C showed after a few minutes a liquid phase on the surface of the solution. For experiment C, this phase was used for dilution. The result of experiment C confirmed the results of the experiments K to M. Due to the fact that it was not possible to filter the solutions in experiments A to C, further preliminary tests were done. Weighed amounts of the homogenised test substance were added in portions to 20 mL distilled water, treated with ultrasonic and stirred for 1 h at 30°C and for approximately 18 h at 20°C. Aliquots of the aqueous phase were taken, centrifuged (30 minutes, 20°C, 15000 rpm) and filtrated (0.2 µm). Aliquots of the filtrate were diluted with distilled water. The concentration of the test substance was determined by HPLC.

 

Table: Additional preliminary tests

 

Experiment

Amount of the test substance (g)

Distilled water (mL)

Dilution with water

Measured concentration (HPLC) in g/L

E

2.99

20

0.021 g - 99.71 g

136

F

5.04

20

0.022 g - 99.79 g

200

G

7.97

20

0.022 g - 99.59 g

294

H

10.02

20

0.023 g - 99.53 g

344

I

12.00

20

0.023 g - 99.57 g

382

J

14.04

20

0.023 g - 99.66 g

412

 

 

Flask-Method

Table: Water solubility of the test item - experiments K to N

 

Experiment

K

L

M

N (Blank)

Amount of test substance (g)

15.87

18.01

14.06

-

Stirring time at 30°C (h)

24

48

72

72

pH at room temperature

5.3

5.4

5.4

7.0

aliquot (g)

0.07831

0.07411

0.08015

0.10682

end volume (g)

99.59

99.61

99.74

99.70

Measured concentration (mg/L)

380.7/377.2

377.6/372.0

358.5/348.8

-

Mean concentration (mg/L)

379

374.8

353.7

-

Water solubility (g/L)

482

503.8

440.1

-

 

Average experiments K to M (without correction for the purity): 475.3 g/L

Standard deviation: 32.4 g/L

Relative standard deviation: 6.8%

 

Table: Concentrations of standards for recheck:

 

Standard

Measured concemtration (mg/L)

% Recovery

Standard F (c= 317.8 mg/L)

331.6

104

Standard A (c =826.9 mg/L)

825.8/826.4

100

 

Recoveries of the 'Recheck samples' ranged between 100% and 104%, indicating a good accuracy of the analytical method.

Conclusions:
Under the study conditions, the water solubility of the test substance at a temperature of 20°C was determined to be 475.3 g/L.
Executive summary:

A study was conducted to determine the water solubility of the test substance, according to OECD Guideline 105 and EU Method A.6, in compliance with GLP.

Due to the fact that it was not possible to stir about five times of the visual estimated quantity with distilled water, only 20 to 23 g of the homogenised test substance were stirred with 20 mL distilled water. Due to the fact that it was not possible to centrifuge and filter in the experiments A to C of the first main test, further preliminary tests were done. Weighed amounts of the homogenised test substance were added in portions to 20 mL distilled water, treated with ultrasonic and stirred for 1 h at 30°C and for approximately 18 h at 20°C. Aliquots of the aqueous phase were taken, centrifuged (30 minutes, 20°C, and 15000 rpm) and filtrated (0.2 µm). Aliquots of the filtrate were diluted with distilled water. The concentrations of the test substance were determined by HPLC.

For the main test, three weighed amounts of the homogenised test substance were added in portions to 20 mL distilled water and stirred for different times at 30°C (experiment K for 24 h, experiment L for 48 h, experiment M and N for 72 h) in tightly closed flasks. After equilibration (24 h at 20°C) aliquots of the saturated aqueous phase were taken and centrifuged (30 minutes, 20°C, 15000 rpm) and filtrated (0.2 µm). Aliquots of the filtrate were diluted with distilled water by weighing the aliquot and the end volume. Due to the fact that the aliquots of the saturated aqueous phases were highly viscous, the aliquots were weighed. The concentration of the test substance was determined by HPLC. Another experiment was performed according to this procedure but without test substance ("blank"= N). 

 

Under the study conditions, the water solubility of the test substance at a temperature of 20°C was determined to be 475.3 g/L.

Description of key information

The water solubility of the test substance at a temperature of 20°C was determined to be 475.3 g/L (Schminke, 2004).

Key value for chemical safety assessment

Water solubility:
475.3 g/L
at the temperature of:
20 °C

Additional information