Zinc didocosanoate

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2017-09-19 to 2017-11-02

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: Tightly closed and dry, room temperature (10 °C – 30 °C), in original container
Handling: Please handle the substance as far as possible under inert gas.

Water solubility:

1.1 µg/L

Conc. based on:

test mat.

Loading of aqueous phase:

1.15 mg/L

Incubation duration:

<= 9 d

Temp.:

20 °C

pH:

>= 6.5 - <= 6.7

Remarks on result:

other: LOQ < 13.3 µg / L

Preliminary test

The preliminary test showed a water solubility of zinc didocosanoate lower than the expected limit of quantification of approximately 0.1 mg / L at 20 °C after measuring the content of zinc in the filtered solutions outside GLP.

Therefore the sponsor decided to carry out the main test with a loading rate of approximately 1 mg test item / L.

Main test

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

The pH of the test solutions and blanks were in the range between 6.5 and 6.7.

In each replicate run the water solubility of the test substance was less than the limit of quantification (LOQ < 13.3 µg / L) of the analytical method.

Measured dissolved zinc concentrations of solutions containing the test item do not continuously increase during the test but vary from 3.6 to 4.5 µg zinc / L. Measured dissolved zinc concentrations of control solutions (i.e. background concentrations) vary from 3.6 to 4.3 µg zinc / L.

A t-test (unpaired, one-sided) was conducted to compare daily mean measured dissolved zinc concentrations of solutions containing the test item with measured zinc concentrations of controls (t-value 0.26). The p-value of the t-test statistic of 0.60 indicates that zinc concentrations of solutions containing the test item are not significantly different from zinc concentrations of controls.

Though statistically not significant, dissolved zinc concentrations of solutions containing the test item are estimated with 0.1 µg zinc/L, i.e. the calculated overall mean background- corrected zinc concentration of solutions containing the test item. Based on the zinc content of zinc didocosanoate of 9.3 %, water solubility is estimated with 1.1 µg zinc didocosanoate/ L.

Measured concentrations of zinc in the solutions

Equilibration time (Days)	Measured concentration in µg zinc / L
	Blank	1st	2nd	Mean (1st & 2nd)	Mean (1st & 2nd) – blank corrected
1	3.7	4.0	3.8	3.9	0.2
2	3.7	3.6	3.8	3.7	0.0
7	3.6	4.1	4.0	4.0	0.5
8	4.2	4.5	4.1	4.3	0.0
9	4.3	4.0	4.5	4.3	0.0
Mean	3.9	4.0	4.0	4.0	0.1
Standard deviation	0.3	0.3	0.3	0.2	0.2
Relative standard deviation (%)	8.6	7.3	7.7	6.0	167.4

Conclusions:

Under the conditions of this test (under exclusion of CO2 and O2, under inert gas; flask method; loadings of 1.14 and 1.16 mg test substance/L), a solubility equilibrium was reached during the first three days of testing. The mean measured amount of dissolved zinc on day 1, 2, 7, 8 and 9 at 20.0 ± 1.0 °C is 0.1 µg/L (determined as dissolved zinc, separated by filtration from undissolved test item). This corresponds to a water solubility of dissolved zinc didocosanoate of 1.1 µg/L, calculated on a zinc content of 9.3 %. Solution pH in samples containing the test item remained at 6.5 – 6.7 while the pH in method blanks ranged from 6.5 – 6.6.

Description of key information

Zinc didocosanoate has a water solubility of 1.1 µg/L at 20 °C.

Key value for chemical safety assessment

Water solubility:

1.1 µg/L

at the temperature of:

20 °C

Additional information

Under the conditions of this test (under exclusion of CO2 and O2, under inert gas; flask method; loadings of 1.14 and 1.16 mg test substance/L), a solubility equilibrium was reached during the first three days of testing. The mean measured amount of dissolved zinc on day 1, 2, 7, 8 and 9 at 20.0 ± 1.0 °C is 0.1 µg/L (determined as dissolved zinc, separated by filtration from undissolved test item). This corresponds to a water solubility of dissolved zinc didocosanoate of 1.1 µg/L, calculated on a zinc content of 9.3 %. Solution pH in samples containing the test item remained at 6.5 – 6.7 while the pH in method blanks ranged from 6.5 – 6.6.