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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:
2017-11-24 to 2018-01-30
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:
Exclusion of CO2 and O2, two vessels was set up in a parallel design at 20 ± 1 °C, each vessel was sampled several times instead of sampling one vessel at every time point.
Qualifier:
according to guideline
Guideline:
EU Method A.6 (Water Solubility)
Version / remarks:
2008
Deviations:
yes
Remarks:
Exclusion of atmospheric CO2 and O2, two vessels was set up in a parallel design at 20 ± 1 °C, each vessel was sampled several times instead of sampling one vessel at every time point.
GLP compliance:
yes
Type of method:
flask method
Specific details on test material used for the study:
Conditions of storage: Store at a dry place at room temperature (10°C – 30°C), in original container
Handling: Please handle the substance as far as possible under inert gas.
Water solubility:
376 mg/L
Conc. based on:
test mat.
Loading of aqueous phase:
2 010 mg/L
Incubation duration:
<= 8 d
Temp.:
20 °C
pH:
>= 6.6 - <= 6.9

Preliminary test

The preliminary test showed a water solubility of "Zinc dioctanoate" of approximately 400 mg / L at 20 °C after measuring the content of zinc in the filtered solutions outside GLP.

Therefore it was decided to carry out the main test with a loading rate of approximately 2,000 mg test item / L.

Main test

The temperature of the water bath was 20 ± 1 °C.

The pH of the test solutions were in the range of 6.6 and 6.9 whereas the pH values of the blanks were in the range of 7.3 and 7.5.

Measured dissolved zinc concentrations of solutions containing the test item do not continuously increase during the test (sampling at day 1, 2, 7 and 8) but vary from 67.4 to 74.7 µg zinc / L. Measured dissolved zinc concentrations of control solutions (i.e. background concentrations) are below the limit of quantification (LOQ).

Based on the zinc content of zinc dioctanoate of 18.6 %, mean water solubility is estimated with 376 mg zinc dioctanoate/ L.

Calculated water solubility of zinc dioctanoate

Equilibration time (Days) Water solubility in mg zinc dioctanoate / L
Blank 

1st

2nd

Mean (1st & 2nd)

1

< 1.29

384

362

373

2

< 1.29

402

382

392

7

< 1.29

367

369

368

8

< 1.29

369

370

370

Mean

< 1.29

381

371

376

Standard deviation

---

16

8

11

 Relative standard deviation (%)

---

4.3

2.2

3.0

Conclusions:
Under the conditions of this test (under exclusion of CO2 and O2, under inert gas; flask method; loadings of 2000.0 mg and 2019.5 mg test substance/L), a solubility equilibrium was reached during the first both days of testing. The mean measured amount of dissolved zinc on day 1, 2, 7 and 8 at 20 ± 1 °C is 69.9 mg/L (determined as dissolved zinc, separated by filtration from undissolved test item). This corresponds to a water solubility of dissolved zinc dioctanoate of 376 mg/L, calculated on a zinc content of 18.6 %. Solution pH in samples containing the test item remained at 6.6 – 6.9 while the pH in method blanks ranged from 7.3 – 7.5.

Description of key information

Zinc dioctanoate has a water solubility of 376 mg/L at 20 °C.

Key value for chemical safety assessment

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

Additional information

Under the conditions of this test (under exclusion of CO2and O2, under inert gas; flask method; loadings of 2000.0 mg and 2019.5 mg test substance/L), a solubility equilibrium was reached during the first both days of testing. The mean measured amount of dissolved zinc on day 1, 2, 7 and 8 at 20 ± 1 °C is 69.9 mg/L (determined as dissolved zinc, separated by filtration from undissolved test item). This corresponds to a water solubility of dissolved zinc dioctanoate of 376 mg/L, calculated on a zinc content of 18.6 %. Solution pH in samples containing the test item remained at 6.6 – 6.9 while the pH in method blanks ranged from 7.3 – 7.5.