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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:
2018-01-16 to 2018-08-16
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 105 (Water Solubility)
Version / remarks:
1995
Deviations:
yes
Remarks:
Two vessels were set up in a parallel design under argon, each vessel was sampled several times instead of sampling one single vessel at each point in time.
Qualifier:
according to guideline
Guideline:
EU Method A.6 (Water Solubility)
Version / remarks:
2008
Deviations:
yes
Remarks:
Two vessels were set up in a parallel design under argon, each vessel was sampled several times instead of sampling one single vessel at each point in time.
GLP compliance:
yes (incl. QA statement)
Remarks:
signed 2016-05-31
Type of method:
flask method
Specific details on test material used for the study:
Storage conditions: Room temperature tightly closed
Water solubility:
3.69 g/L
Conc. based on:
test mat. (dissolved fraction)
Loading of aqueous phase:
4 000.34 mg/L
Incubation duration:
>= 1 - <= 3 d
Temp.:
20 °C
pH:
10.5
Remarks on result:
other: 1st test
Key result
Water solubility:
33.8 g/L
Conc. based on:
test mat. (dissolved fraction)
Loading of aqueous phase:
40.024 g/L
Incubation duration:
>= 25 - <= 27 d
Temp.:
20.02 °C
pH:
>= 10.9 - <= 11.3
Remarks on result:
other: 2nd test
Remarks:
S.D.: ± 1.1 g/L; result calculated based on a purity of 99 %
Key result
Water solubility:
34.2 g/L
Conc. based on:
test mat. (dissolved fraction)
Remarks:
Strontium bis(2-ethylhexanoate)
Loading of aqueous phase:
40.024 g/L
Incubation duration:
>= 25 - <= 27 d
Temp.:
20.02 °C
pH:
>= 10.9 - <= 11.1
Remarks on result:
other: 2nd test
Remarks:
S.D.:± 1.1 g/L; result calculated based on a purity of 100 %
Details on results:
Temperature and oxygen
- The mean temperature was 20.4 ± 0.5 °C (1st test), 20.2 ± 0.5 °C in the 2nd test .
- No oxygen was measurable
- pH values for samples: 1st test: 10.51 – 10.54 (days 1–3), 2nd test: 10.89 - 11.31 (days 10-27)
- pH values for blanks: 1st test: 6.57 (3d) - 7.54 (1d), 2nd test: 4.18 (10d) – 5.75 (27d)
- The turbidity in samples from both tests were always <1 NTU indicating that filtered solutions did not contain any undissolved material
- Analytical measurements: The low concentrations [µg/L] in method blanks from both tests will not be subtracted due to the high concentration [g/L] in the test item loaded samples. The calculated variations/changes between the sampling points were less than 15 % for all days and no tendency of increasing was observed. Thus, the validity criteria as foreseen in OECD 105 and Regulation 440/2008/EC A.6 were fulfilled.

ICP-OES measurement with corresponding LOD/LOQ, correlation coefficient and sum of quality assurance samples and recovery

Calibration [µg/L] – lowest and highest calibration point

Chosen wavelength [nm]

LOD
[µg/L]

LOQ
[µg/L]

correlation coefficient

Sum of quality assurance samples

Recovery / validity of quality assurance samples [%]

1st test - January 24, 2018 - measurement of all samples, only method blanks used, test item samples all above calibration

1 – 1000 (total of 13 calibration points, 13 used + blank)

Sr: 421.552

Sr: 0.021

Sr: 0.064

Sr: 0.999968

Sr: 20

Sr: 100

1st test - January 29, 2018 - re-measurement of test item samples, since strontium content of test item samples (1st measurements were not within calibration range)

1 – 1000 (total of 13 calibration points, 13 used + blank)

Sr: 421.552

Sr: 0.024

Sr: 0.071

Sr: 0.999980

Sr: 23

Sr: 91.3

2nd test - July 31, 2018 – test item samples and method blanks of d11

25 – 1000 (total of 13 calibration points, 8 used + blank)

Sr: 215.283

Sr: 1.26

Sr: 3.77

Sr: 0.999988

Sr: 21

Sr: 100

2nd test - August 01, 2018 – test item samples and method blanks of d12

1 – 1000 (total of 13 calibration points, 13 used + blank)

Sr: 421.552

Sr: 0.007

Sr: 0.021

Sr: 0.999965

Sr: 21

Sr: 100

2nd test - August 02, 2018 – test item samples and method blanks of d13

1 – 1000 (total of 13 calibration points, 13 used + blank)

Sr: 216.596

Sr: 0.441

Sr: 1.32

Sr: 0.999964

Sr: 21

Sr: 100

2nd test - August 14, 2018 – test item samples and method blanks of d25

1 – 1000 (total of 13 calibration points, 13 used + blank)

Sr: 407.771

Sr: 0.006

Sr: 0.019

Sr: 0.999131

Sr: 13

Sr: 100

2nd test - August 15, 2018 – test item samples and method blanks of d26

1 – 1000 (total of 13 calibration points, 13 used + blank)

Sr: 216.596

Sr: 0.410

Sr: 1.23

Sr: 0.999986

Sr: 13

Sr: 100

2nd test - August 16, 2018 – test item samples and method blanks of d27

1 – 1000 (total of 13 calibration points, 13 used + blank)

Sr: 407.771

Sr: 0.006

Sr: 0.019

Sr: 0.999112

Sr: 13

Sr: 100

Recovery/validation data for strontium

Element Sr

Recovery [%]

SD [%]

n (total)

n (valid)

January 24, 2018 (1st test)

TMDA-70.2 nominal value Sr: 449 µg/L

101

1

4

4

Quality control standard (Roth) 7.5 µg/L

101

2

4

4

Quality control standard (Roth) 75 µg/L

101

2

4

4

Quality control standard (Roth) 750 µg/L

97.3

0.6

4

4

Recalibration standard 100 µg/L

101

2

4

4

January 29, 2018 (1st test)

TMDA-70.2 nominal value Sr: 449 µg/L

101

1

4

4

Quality control standard (Roth) 7.5 µg/L

103

1

5

4

Quality control standard (Roth) 75 µg/L

101

1

5

4

Quality control standard (Roth) 750 µg/L

95.9

0.9

4

4

Recalibration standard 100 µg/L

104

1

4

4

July 31, 2018 (2nd test)

TMDA-70.2 nominal value Sr: 449 µg/L

(dilution 2-fold) => 224.5 µg/L Sr

99.1

1.7

5

5

Quality control standard (Roth) 100 µg/L

97.4

1.4

5

5

Quality control standard (Roth) 750 µg/L

94.9

0.2

5

5

Recalibration standard 500 µg/L

98.5

0.8

5

5

August 01, 2018 (2nd test)

TMDA-70.2 nominal value Sr: 449 µg/L

 (dilution 2-fold) => 224.5 µg/L Sr

99.2

1.5

5

5

Quality control standard (Roth) 100 µg/L

99.4

0.7

5

5

Quality control standard (Roth) 750 µg/L

94.8

0.6

5

5

Recalibration standard 500 µg/L

98.4

1.4

5

5

August 02, 2018 (2nd test)

TMDA-70.2 nominal value Sr: 449 µg/L

(dilution 2-fold) => 224.5 µg/L Sr

101

1

5

5

Quality control standard (Roth) 100 µg/L

98.1

1.1

5

5

Quality control standard (Roth) 750 µg/L

96.0

2.0

5

5

Recalibration standard 500 µg/L

99.1

1.3

5

5

August 14, 2018 (2nd test)

TMDA-70.2 nominal value Sr: 449 µg/L

(dilution 2-fold) => 224.5 µg/L Sr

103

<1

3

3

Quality control standard (Roth) 100 µg/L

102

1

3

3

Quality control standard (Roth) 750 µg/L

101

1

3

3

Recalibration standard 500 µg/L

104

1

3

3

August 15, 2018 (2nd test)

TMDA-70.2 nominal value Sr: 449 µg/L

(dilution 2-fold) => 224.5 µg/L Sr

99.7

1.1

3

3

Quality control standard (Roth) 100 µg/L

98.2

0.2

3

3

Quality control standard (Roth) 750 µg/L

96.0

1.0

3

3

Recalibration standard 500 µg/L

99.5

1.2

3

3

August 16, 2018 (2nd test)

TMDA-70.2 nominal value Sr: 449 µg/L
(dilution 2-fold) => 224.5 µg/L Sr

103

<1

3

3

Quality control standard (Roth) 100 µg/L

102

1

3

3

Quality control standard (Roth) 750 µg/L

101

1

3

3

Recalibration standard 500 µg/L

104

<1

3

3

Strontium fortification

sample

element

measured concentration [µg/L]

calculated level after addition [µg/L]

recovery
[µg/L] / [%]

January 29, 2018 (1st test)

Vessel 1 sample a 2d sampling; dilution factor 1000; 1 mL sample + 4 mL 250 µg/L standard

Sr

883

377

371/ 98.6

July 31, 2018 (2nd test)

Vessel 1 sample a 11d sampling; dilution factor 10000; 1 mL sample + 4 mL 75 µg/L standard

Sr

771

214

213/ 99.5

August 01, 2018 (2nd test)

Vessel 1 sample a 12d sampling; dilution factor 10000; 1 mL sample + 4 mL 75 µg/L standard

Sr

759

212

211/ 99.8

August 02, 2018 (2nd test)

Vessel 1 sample a 13d sampling; dilution factor 10000; 1 mL sample + 4 mL 75 µg/L standard

Sr

727

205

206/ 100

August 14, 2018 (2nd test)

Vessel 1 sample a 25d sampling; dilution factor 10000; 1 mL sample + 4 mL 250 µg/L standard

Sr

781

356

370/ 104

August 15, 2018 (2nd test)

Vessel 1 sample a 26d sampling; dilution factor 10000; 1 mL sample + 4 mL 100 µg/L standard

Sr

801

240

241/ 100

August 16, 2018 (2nd test)

Vessel 1 sample a 27d sampling; dilution factor 10000; 1 mL sample + 4 mL 250 µg/L standard

Sr

828

366

374/ 102

1st test

The pH value of solutions containing the test item was in the range of 10.51 – 10.54 during testing (days 1 – 3). The pH value in method blanks was in the range of 7.25 – 7.54 at day 1 and decreased during testing (day 3: pH 6.57 – 6.71).The test item reacts basic upon dissolution in water.

The strontium measurements were performed by ICP-OES.

The determination of the water solubility of Strontium bis(2-ethylhexanoate) is based on mean dissolved strontium concentrations of sampling days (1, 2, 3 d) and a strontium amount of 23.3 % in the test item. The amount of dissolved Strontium bis(2-ethylhexanoate) was calculated with a test item purity of 99 % according to test substance data sheet and 100 % as follows: Mean Sr concentrations:

                           Vessel 1:       0.880 ± 0.008 g/L

                           Vessel 2:       0.856 ± 0.044 g/L

                           Mean:              0.868 ± 0.033 g/L

Based on a test item purity of 99 % the water solubility of Strontium bis(2-ethylhexanoate) is: Mean of concentration x 99 % / 23.3 %:

                           Vessel 1:       3.74 ± 0.03 g/L

                           Vessel 2:       3.64 ± 0.19 g/L

                           Mean:              3.69 ± 0.14 g/L

Based on a test item purity of 100 % the water solubility of Strontium bis(2-ethylhexanoate): Mean of concentration x 100 % / 23.3 %:

                           Vessel 1:       3.77 ± 0.03 g/L

                           Vessel 2:       3.67 ± 0.19 g/L

                           Mean:              3.72 ± 0.14 g/L

However, the mean strontium concentration was analysed to 0.868 ± 0.033 g Sr/L that is calculated to a water solubility for strontium bis(2-ethylhexanoate) of 3.69 ± 0.14 g/L (sampling day 1, 2 and 3) at 20 ± 1 °C. Based on the preliminary test a loading for the main test of 4 g/L test item was chosen. Considering the loading and the test result it became obvious that the loading chosen for the main test was too low. Furthermore, no undissolved material was observed in test item loaded vessels. Hence, it was decided to repeat the study using a loading of 40 g/L.

2nd test

For the second test, 32 g of the test item were weighed into 800 mL of argon purged water (32.029 g and 32.010 g in vessel 1 and 2, respectively).

The pH value of solutions containing the test item started at 11.3 at day 10 and decreased over the seven sampling points (day 27: pH 10.9 – 11.1). The pH value in method blanks was in the range of 4.2 (lowest value method blank 2) – 5.8 (highest value method blank 1) within testing. The pH value in method blank 2 is always 4.2. This might be due to a slight acid residue caused by rinsing with acid before measurement?. The test item reacts basic upon dissolution in water.

The determination of the water solubility of Strontium bis(2-ethylhexanoate) is based on mean dissolved strontium concentrations of sampling days (25, 26 and 27 day) and a strontium amount of 23.3 % in the test item. The amount of dissolved strontium bis(2-ethylhexanoate) in the 2nd test was calculated with a test item purity of 99 % according to test substance data sheet and 100 % as follows: Mean Sr concentrations:

                           Vessel 1:       8.00 ± 0.25 g/L

                           Vessel 2:       7.93 ± 0.30 g/L

                           Mean:              7.96 ± 0.27 g/L

Based on a test item purity of 99 % the water solubility of Strontium bis(2-ethylhexanoate) is: Mean of concentration x 99 % / 23.3 %:

                           Vessel 1:       34.0 ± 1.1 g/L

                           Vessel 2:       33.7 ± 1.3 g/L

                           Mean:             33.8 ± 1.1 g/L

Based on a test item purity of 100 % the water solubility of Strontium bis(2-ethylhexanoate): Mean of concentration x 100 % / 23.3 %:

                           Vessel 1:       34.3 ± 1.1 g/L

                           Vessel 2:       34.0 ± 1.3 g/L

                           Mean:              34.2 ± 1.1 g/L

Conclusions:
1st test
Under the conditions of this test (under exclusion of CO2 and O2, under inert gas; flask method; loadings of 4.00 g/L a vessel 1 and 2, solubility equilibrium was observed during testing. The mean measured amount of dissolved strontium at 20 ± 1 °C is 0.868 ± 0.033 g/L (determined as dissolved strontium, separated by filtration from undissolved test item). This corresponds to a water solubility of strontium bis(2-ethylhexanoate) of 3.69 ± 0.14 g/L, calculated on a strontium content of 23.3 % and a test substance purity of 99 % (w/w).
These results indicate a nearly complete dissolution of the test item in the first test. Therefore, a second test with a higher loading has been conducted.

2nd test
Under the conditions of this test (under exclusion of CO2 and O2, under inert gas; flask method; loadings of 40.04 and 40.01 g/L test substance in vessel 1 and 2, a solubility equilibrium was observed during the whole testing. The mean measured amount of dissolved strontium at 20.2 ± 0.5 °C is 7.96 ± 0.27 g/L (determined as dissolved strontium on day 25, 26, 27, separated by filtration from undissolved test item). This corresponds to a water solubility of strontium bis(2-ethylhexanoate) of 33.8 ± 1.1 g/L, calculated on a strontium content of 23.3 % and a test substance purity of 99 % (w/w). Based on a test substance purity of 100 % (w/w), the water solubility of Strontium bis(2-ethylhexanoate) is calculated to 34.2 ± 1.1 g/L.

Description of key information

Based on a test substance purity of 100 % (w/w), the water solubility of Strontium bis(2-ethylhexanoate) is calculated to 34.2 ± 1.1 g/L.

Key value for chemical safety assessment

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

Additional information

1st test

Under the conditions of this test (under exclusion of CO2 and O2, under inert gas; flask method; loadings of 4.00 g/L a vessel 1 and 2, solubility equilibrium was observed during testing. The mean measured amount of dissolved strontium at 20 ± 1 °C is 0.868 ± 0.033 g/L (determined as dissolved strontium, separated by filtration from undissolved test item). This corresponds to a water solubility of strontium bis(2-ethylhexanoate) of 3.69 ± 0.14 g/L, calculated on a strontium content of 23.3 % and a test substance purity of 99 % (w/w).

These results indicate a nearly complete dissolution of the test item in the first test. Therefore, a second test with a higher loading has been conducted.

2nd test

Under the conditions of this test (under exclusion of CO2 and O2, under inert gas; flask method; loadings of 40.04 and 40.01 g/L test substance in vessel 1 and 2, a solubility equilibrium was observed during the whole testing. The mean measured amount of dissolved strontium at 20.2 ± 0.5 °C is 7.96 ± 0.27 g/L (determined as dissolved strontium on day 25, 26, 27, separated by filtration from undissolved test item). This corresponds to a water solubility of strontium bis(2-ethylhexanoate) of 33.8 ± 1.1 g/L, calculated on a strontium content of 23.3 % and a test substance purity of 99 % (w/w). Based on a test substance purity of 100 % (w/w), the water solubility of Strontium bis(2-ethylhexanoate) is calculated to 34.2 ± 1.1 g/L.