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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:
May 04 - 18, 2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 105 (Water Solubility)
Qualifier:
according to guideline
Guideline:
EU Method A.6 (Water Solubility)
GLP compliance:
yes (incl. QA statement)
Remarks:
Rheinland Pfalz, Landesamt für die Umwelt
Type of method:
flask method
Water solubility:
3.51 mg/L
Incubation duration:
>= 0 - <= 4 d
Temp.:
20 °C
pH:
>= 6.01 - <= 6.41

Main Test 1

Setup

To determine a dependency of the water solubility on the amount of the test item added, six different loading rates were chosen: 50 mg/L (flask 2), 100 mg/L (flask 3), 200 mg/L (flasks 1A – 1C), 300 mg/L (flask 4), 400 mg/L (flask 5), 500 mg/L (flask 6). Three replicates were prepared with the same loading rate 200 mg/L (flasks 1A, 1B, 1C) and used in the equilibration time.

The following amounts were added to the flasks:

Content of Flasks

No.

Amount test item in mg

Volume H2O in mL

Resulting nominal concentration in mg/L

1A

40.0

200

200

1B

40.2

200

201

1C

40.0

200

200

2

5.1

100

51

3

10.1

100

101

4

30.0

100

300

5

40.1

100

401

6

50.2

100

502

Flask 1A was intended for the sampling point 24h, flask 1B for the sampling point 48h and flask 1C for the sampling point 72h. A preincubation at 30°C was not used to avoid an oversaturation of the solution.

Performance

Six vessels [flasks 1C (for the sampling point 72 h) and flasks 2 – 6] were set onto the shaking apparatus immediately and shaking at 200 rpm was started. After 24 ± 2 hours, flask 1B (for the sampling point 48 h) and after 48 ± 2 hours, flask 1A (for the sampling point 24 h) were set on the shaker and all flasks were shaken for further 24 ± 2 hours at room temperature.

Then, flasks 1A-C were taken from the shaker, samples were taken from the flasks, mem-brane filtrated via 0.45 μm PTFE filters and extracted. Due to a difference of more than 15 % in the concentrations on days 2 and 3 (flasks 1B and 1C), the test was prolonged and the flask 1C was measured in day 4.

Because of a difference of less than 15 % in the concentrations on days 2 and 4 and no upward tendency, the test was finished on day 4. The value from the flaks 1C (3 d) was stated as an outlier and was not used in the calculation. The final measurement was performed as determination from flasks 2 – 6 in the same way. All filtrated test solutions showed no Tyndall effect (i.e. a laser beam was not scattered when transmitted through the liquid). A slightly Tyndall effect was observed in the filtrated solution from the flask 4.

Main Test 2

Setup

Due to a water solubility of the test item determined in the main test 1 lower than 5 mg/L and a high RSD of the result, the main test was repeated using the slow-stirring flask method. The test item was melted at 80 °C before usage. The same nominal loads were used:

Content of Flasks

Flask No.

Amount test item in mg

Volume H2O in mL

Resulting nominal concentration in mg/L

1A

40.0

200

200

1B

40.1

200

201

1C

40.0

200

200

2

5.1

100

51

3

10.0

100

100

4

30.0

100

300

5

40.1

100

401

 6  50.2  100  502

Performance

Six vessels [flasks 1C (for the sampling point 72 h) and flasks 2 – 6] were set onto the magnetic stirrer immediately and stirring at 100 rpm was started. After 24 ± 2 hours, flask 1B (for the sampling point 48 h) and after 48 ± 2 hours, flask 1A (for the sampling point 24 h) were set on the stirrer and all flasks were stirred for further 24 ± 2 hours at room temperature (20.0 ± 0.5 °C).

Then, flasks 1A-C were taken from the stirrer, samples were taken, membrane filtrated via 0.45 μm PTFE filters and extracted. Due to a difference of more than 15 % in the concentrations on days 2 and 3 (flasks 1B and 1C), the test was prolonged and the flask 1C was measured in day 4.

Because of a difference of less than 15 % in the concentrations on days 3 and 4 and no upward tendency, the test was finished on day 4.

The final measurement was performed as determination from flasks 2 – 6 in the same way. All filtrated test solutions showed no Tyndall effect (i.e. a laser beam was not scat-tered when transmitted through the liquid).

FINDINGS TEST 1

The following values were observed in the flasks 2 – 6:

Flask

Temperature [°C]

pH

Concentration [mg/L]

Total Mean [mg/L]

Total Standard Deviation [mg/L] (RSD** [%])

1*

20.0

6-7

3.83

3.44

 

0.45 (13.0 %)

2

19.5

5.71

2.91

 

3

19.5

6.29

3.84

4

19.5

5.90

4.75***

5

19.5

6.15

3.02

6

19.5

6.51

3.61

*mean value of flasks 1A – 1C (days 1, 2 and 4)

**RSD = relative standard deviation

***as a slightly Tyndall-effect was observed in the filtrated solution, the flask was not used in the evaluation

Mean at the plateau is 3.44 ± 0.45 mg/L.

The ratio of two signals 1 and 2 in all test vessels was 97.5 % : 2.5 % (mean value).

FINDINGS TEST 2

Flask

Temperature [°C]

pH

Concentration [mg/L]***

Total Mean [mg/L]

Total Standard Deviation [mg/L] (RSD** [%])

1*

20.0

6-7

2.97

3.51

 

0.66 (18.8 %)

2

20.5

6.23

2.86

 

3

20.5

6.01

2.93

4

20.5

6.21

4.14

5

20.5

6.11

3.90

6

20.5

6.41

4.26

*mean value of flasks 1A – 1C (days 1 – 4)

**RSD = relative standard deviation

***recovery rate of QC sample 95.8 % was taken into account in the calculation

Mean at the plateau is 3.51 ± 0.66 mg/L.

The ratio of two signals 1 and 2 in all test vessels was 99.0 % : 1.0 % (mean value). The flask 1C (4d) was not used in the calculation of the area ratio as the value was stated as an outlier.

Description of key information

3.51 ± 0.66 mg/L at 20.0 ± 0.5 °C, pH = 6.01 - 6.41 (OECD 105 / EU A.6, slow-stirring flask method)

Key value for chemical safety assessment

Water solubility:
3.51 mg/L
at the temperature of:
20 °C

Additional information

3.51 ± 0.66 mg/L at 20.0 ± 0.5 °C, pH = 6.01 - 6.41 (slow-stirring flask method)