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Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

05 August 2019 - 13 August 2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

The determination of water solubility was performed using the slow stirring method adapted from OECD Guideline No 123, OECD Guideline No 105 and Method A.6. This study was considered as reliable without restrictions because it was conducted under GLP.

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Qualifier:

according to guideline

Guideline:

other: adapted from OECD Guideline 123

Deviations:

no

Principles of method if other than guideline:

In a stirring vessel maintained at 20 +/- 0.5°C, ultra-pure water containing the test item poured into the top of the vessel was slow stirred. The stirring rate was adjusted in order to form a minimal vortex. The aim of this method was to prevent the formation of emulsions when saturating water. Emulsions can be formed with the shake flask method and lead to a solubility overestimation. The water solubility was given by the mass concentration of the substance in water when it reached a plateau as a function of time. Two experiments were performed in the same conditions

GLP compliance:

yes (incl. QA statement)

Remarks:

2018-11-15

Type of method:

other: slow-stirring method

Water solubility:

24.64 mg/L

Temp.:

20 °C

pH:

>= 4.83 - <= 5.78

Remarks on result:

other: First determination (vessel 1)

Water solubility:

24.69 mg/L

Temp.:

20 °C

pH:

>= 4.74 - <= 5.78

Remarks on result:

other: Second determination (vessel 2)

Key result

Water solubility:

ca. 24.67 mg/L

Temp.:

20 °C

pH:

>= 4.74 - <= 5.78

Remarks on result:

other: Mean of two solubility values obtained in two different experiments.

Preliminary test

A preliminary test was carried out as a range finding test prior to the main test. The concentration range obtained gave an indication on the necessary analytical method sensitivity.

Increasing volumes of water were added at room temperature to  22.0 mg of the test sample in a 100 mL flask. After each addition of an amount of water, the mixture was shaken for 10 minutes and was visually checked for any undissolved parts of the sample.

The approximate solubility deduced from the necessary volume of water in which complete dissolution of the sample occurred is given in the table below.

 

Volume of water added	Solubilisation ?	Approximate solubility
1 mL	NO	-
10 mL	NO	-
100 mL	NO	< 217 mg/L

 

The test item (22.0 mg) was not solubilized by a water volume of 100 mL, corresponding to a solubility below 217 mg/L (taking into account the test item purity of 98.6 %).

 

Main test:

The following table presents the concentrations (in mg/L) obtained during the study for the two vessels. The sampling in the vessel 2 only started when the concentrations observed in the vessel 1 approached an equilibrium state.

Sampling date (m/d/y)	Vessel 1	Vessel 2
08/05/19 8:15 (Preparation)	-	-
08/07/19 8:00	24.91	-
08/07/19 13:15	23.60	-
08/08/19 8:10	24.67	-
08/08/19 13:20	24.26	24.47
08/09/19 7:55	24.48	24.63
08/09/19 13:10	24.76	23.79
08/12/19 8:35	25.83	25.88
08/12/19 13:35	24.04	24.29
08/13/19 7:45	24.11	24.85

 

These concentrations are presented as a function of time in the figure.

 

The pH values measured in both systems were:
- 5.78 in both systems at the beginning of the experiment.
- 4.83 in vessel 1 and 4.74 in vessel 2 at the end of the experiment.
The pH controlled with the indicator strips for each specimen was 5 for all the samples taken from the two vessels.
The temperature variations were included in the range 19.8 °C - 20.3 °C.

 

Equilibrium demonstration:

 

The equilibrium state was declared on August 13, at 7:45. The following table demonstrates that the equilibrium criteria are valid for each vessel.

 

Criteria	Vessel 1	Vessel 2
Maximum difference observed in the 5 last samples	Min: 24.04 mg/L        Max: 25.83 mg/L Difference: 7.2 %	Min: 23.79 mg/L        Max: 25.88 mg/L Difference: 8.4 %
Conclusion	Equilibrium reached	Equilibrium reached

Water solubility calculation:

The means of the five samples before the equilibrium state declaration (08/13/2019 7:45) for each vessel are:
- 24.64 mg/L for vessel 1;
- 24.69 mg/L for vessel 2.
The difference observed between the two determinations is 0.20 %, which proves that an acceptable repeatability is obtained (the OECD 105 acceptability criterion for the maximum difference between two tests by the column elution method is 30 % and 15 % for the shake flask method).
The test item solubility in water is given by the mean of the values obtained for the two vessels: 24.67 mg/L.

Conclusions:

Based on two determinations with the slow-stirring method, the test item ST 08 C 19 solubility in water at 20 ± 0.5 °C was 24.67 mg/L.

Executive summary:

A study was performed to assess the water solubility of the test item by the slow stirring method.

Two determinations in ultrapure water were carried out. 5 mL of the test item were carefully poured at the top of 250 mL of water thermostated at 20 + 0.5°C. The systems were allowed to equilibrate one day before starting the sampling and up to 8 days. The test item concentrations were monitored by HPLC-DAD.

The test item solubility in water at 20 ± 0.5 °C based on two determinations with the slow-stirring method was 24.67 mg/L.

Description of key information

Water Solubility: 24.64 mg/L at 20.0 ± 0.5 °C, EU Method A.6, 2020

Key value for chemical safety assessment

Water solubility:

24.64 mg/L

at the temperature of:

20 °C

Additional information

Kes Study :A study was performed to assess the water solubility of the test item by the slow stirring method.

Two determinations in ultrapure water were carried out. 5 mL of the test item were carefully poured at the top of 250 mL of water thermostated at 20 + 0.5°C. The systems were allowed to equilibrate one day before starting the sampling and up to 8 days. The test item concentrations were monitored by HPLC-DAD.

The test item solubility in water at 20 ± 0.5 °C based on two determinations with the slow-stirring method was 24.67 mg/L.