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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:
2018-05-30 to 2018-06-07
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, each vessel was sampled several times instead of sampling one vessel at every point in time/ exclusion of O2 and CO2, under inert gas (argon)
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, each vessel was sampled several times instead of sampling one vessel at every point in time/ exclusion of O2 and CO2, under inert gas (argon)
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:
Appearance: Green powder
Storage conditions: Keep container tightly closed, in a dry place at room temperature.
Water solubility:
52.5 mg/L
Conc. based on:
element (dissolved fraction)
Remarks:
Cu
Loading of aqueous phase:
2 other: test item/L
Incubation duration:
>= 1 - <= 3 d
Temp.:
19.1 °C
pH:
>= 4.6 - <= 4.7
Remarks on result:
other: S.D.: ± 0.6 mg Cu/L
Water solubility:
340 mg/L
Conc. based on:
test mat. (dissolved fraction)
Loading of aqueous phase:
2 g/L
Incubation duration:
>= 1 - <= 3 d
Temp.:
19.1 °C
pH:
>= 4.6 - <= 4.7
Remarks on result:
other: S.D.: ± 4 mg/L
Remarks:
calculated based on a mean dissolved copper concentrations of 52.5 ± 0.6 mg/L and a copper amount of 15.42 % in the test item.
Details on results:
- The mean temperature was 19.1 ± 0.3 °C
- No oxygen was detectable
- The pH of test item solutions remained between 4.6 – 4.7, whereas the pH of the method blanks ranged between 6.4 – 7.3
- The turbidity in samples from the test was always < 1 NTU indicating that filtered solutions did not contain any undissolved material
- Validation: recovery was in the range of 100 ± 15 % of the respective certified value or the nominal/calculated values.

ICP-OES analysis 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 of quality assurance samples [%]

June 06, 2018; measurement of test samples and method blanks (1d, 2d)

2.5 – 1000 (total of 13 calibration points, 12 used + blank)

219.227

1.46

4.37

0.999941

32

87.5

June 07, 2018; measurement of test samples and method blanks (3d)

1.0 – 1000 (total of 13 calibration points, 13 used + blank)

219.227

2.36

7.07

0.999980

16

100

 

Recovery/validation data copper of measurement series

Element Cu

Recovery [%]

SD [%]

n (total)

n (valid)

June 06, 2018

TMDA-70.2 (dilution factor 2), nominal value Cu: 406 µg/L – diluted 203 µg/L

102

13

6

5

Quality control standard (Roth) 5 µg/L

106

16

6

5

Quality control standard (Roth) 100 µg/L

105

1

6

6

Quality control standard (Roth) 750 µg/L

105

1

6

6

Recalibration standard 50 µg/L

98.1

1.2

6

4

June 07, 2018

TMDA-70.2 (dilution factor 2), nominal value Cu: 406 µg/L – diluted 203 µg/L

103

1

3

3

Quality control standard (Roth) 5 µg/L

97.3

4.4

3

3

Quality control standard (Roth) 100 µg/L

102

1

3

3

Quality control standard (Roth) 750 µg/L

102

1

3

3

Recalibration standard 50 µg/L

99.2

1

3

3

 

Selected samples were fortified with a known amount of copper (by standard addition of commercial standard) to determine the standard recoveries of this element.

Fortification of measurement series

Sample

Element

Measured concentration [µg/L]

Calculated level after addition [µg/L]

Recovery
[µg/L] / [%]

June 06, 2018

Vessel 1 sample a 1d (dilution 100-fold) – 1 mL sample 4 mL 100 µg/L standard

Cu

526

185

180 / 96.9

Vessel 1 sample a 2d (dilution 100-fold) – 1 mL sample 4 mL 250 µg/L standard

Cu

524

305

320 / 105

June 07, 2018

Vessel 1 sample a 3d (dilution 100-fold) – 1 mL sample 4 mL 100 µg/L standard

Cu

399

160

164 / 103

 

Calculation of water solubility according to a copper content of 15.42 % in test item.

Cu conc. [mg/L]

Mean Cu conc. [mg/L]

SD [mg/L]

Mean Cu both vessels [mg/L]

SD [mg/L]

Cu in test item [%]

Calculated amount of test item dissolved on basis of Cu [mg/L]

Mean dissolved test item [mg/L]

SD [mg/L]

Mean both vessels [mg/L]

SD [mg/L]

vessel 1 day 1 sample a

52.6

52.6

0.4

52.5

0.6

15.42

341

341

3

340

4

vessel 1 day 1 sample b

52.1

338

vessel 1 day 2 sample a

52.4

340

vessel 1 day 2 sample b

52.7

342

vessel 1 day 3 sample a

39.9$

$

vessel 1 day 3 sample b

53.2

345

vessel 2 day 1 sample a

51.9

52.4

0.7

337

340

4

vessel 2 day 1 sample b

51.3

333

vessel 2 day 2 sample a

53.0

344

vessel 2 day 2 sample b

52.9

343

vessel 2 day 3 sample a

52.8

343

vessel 2 day 3 sample b

52.5

341

$  Outlier according to Shapiro Wilks and Grubbs test, not used for calculations

The water solubility of 2-ethylhexanoic acid, copper salt is based on mean dissolved copper concentrations of sampling days 1, 2, 3 and a copper amount of 15.42 % in the test item. The amount of dissolved 2-ethylhexanoic acid, copper salt was calculated as follows:

 

Mean copper concentrations analysed:

Vessel 1:       52.6 ± 0.4 mg/L

Vessel 2:       52.4 ± 0.7 mg/L

Mean:            52.5 ± 0.6 mg/L

 

Mean copper concentration x 100 % / 15.42 %:

Vessel 1:       341 ± 3 mg/L

Vessel 2:       340 ± 4 mg/L

Mean:            340 ± 4 mg/L 

Conclusions:
Under the conditions of this test (under exclusion of CO2 and O2, under inert gas; flask method; loadings of 2 g test item/L ultrapure water) solubility equilibrium was observed during testing on three consecutive days (variations between subsequent sampling points were less than 15 % and no increasing copper values were observed). The analysed dissolved copper concentration at 19.1 ± 0.3 °C is 52.5 ± 0.6 mg/L (determined as dissolved copper, separated by filtration < 0.2 µm from undissolved test item). This corresponds to a water solubility of 2-ethylhexanoic acid, copper salt of 340 ± 4 mg/L, calculated on a copper content of 15.42 %.
The pH of test item solutions remained between 4.6 – 4.7, whereas the pH of the method blanks ranged between 6.4 – 7.3.

Description of key information

2-Ethylhexanoic acid, copper salt has a water solubility of 340 ± 4 mg/L at 19.1  ± 0.3 °C.

Key value for chemical safety assessment

Water solubility:
340 mg/L
at the temperature of:
19.1 °C

Additional information

Under the conditions of this test (under exclusion of CO2and O2, under inert gas; flask method; loadings of 2 g test item/L ultrapure water solubility) equilibrium was observed during testing on three consecutive days (variations between subsequent sampling points were less than 15 % and no increasing copper values were observed). The analysed dissolved copper concentration at 19.1 ± 0.3 °C is 52.5 ± 0.6 mg/L (determined as dissolved copper, separated by filtration < 0.2 µm from undissolved test item). This corresponds to a water solubility of 2-ethylhexanoic acid, copper salt of 340 ± 4 mg/L, calculated on a copper content of 15.42 %.

The pH of test item solutions remained between 4.6 – 4.7, whereas the pH of the method blanks ranged between 6.4 – 7.3.