Zirconium dinitrate oxide

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2015-04-29 to 2015-05-08

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

flask method

Water solubility:

166 g/L

Temp.:

10 °C

pH:

0.52

Remarks on result:

other: without pH adjustment

Key result

Water solubility:

169 g/L

Temp.:

20 °C

pH:

0.48

Remarks on result:

other: without pH adjustment

Water solubility:

< 0.4 mg/L

Temp.:

10 °C

pH:

4.02

Remarks on result:

other: with pH adjustment to pH 4

Water solubility:

< 0.4 mg/L

Temp.:

20 °C

pH:

4.02

Remarks on result:

other: with pH adjustment to pH 4

Water solubility:

< 0.05 mg/L

Temp.:

20 °C

pH:

9

Remarks on result:

other: with pH adjustment to pH 7

Water solubility:

< 0.05 mg/L

Temp.:

20 °C

pH:

9

Remarks on result:

other: with pH adjustment to pH 9

Details on results:

Preliminary experiment 1:
ICP-AES measurement of dissolved Zr without pH adjustment of the test solution indicated that water solubility is > 100 g/L. Between pH 4 and 7, all Zr precipitated from the test solution, as no measurable dissolved Zr levels could be observed from pH 7 on.

Preliminary experiment 2:
ICP-MS measurement of dissolved Zr without pH adjustment of the test solution (nominal loading rate 10 g test item/L) yielded a water solubility of 7.98 g/L. The following results were obtained at different pH levels:
- pH 4: 1.13 g/L
- pH 7: < 0.05 g/L
- pH 9: < 0.05 g/L

However, these results of preliminary experiment 2 should be considered with caution because:
- ICP-MS showed too low recoveries (80%) due to physical interference caused by the special properties of the test item, therefore it was decided to change to ICP-AES in the main test. For ICP-AES, the recoveries were effectively much higher and confirmed the composition of the test item as indicated by the sponsor.

Main test:
In the main test using ICP-AES, the following conditions were also applied:
- Loading rate in the main test was much higher as in preliminary experiment 2 (as was already clear from the first preliminary experiment).
- It was decided not to include the pH 7 and 9 adjustments in the main test as the physical interference had no influence on the quantification limit and it was proven in the two preliminary experiments that at pH 7 and 9 all results were below the quantification limit.

Preliminary information (non-GLP) revealed that the water solubility was higher than 100 g/L test item. Attemps made with 300 and 500 g/L were not successful because the solutions could not be stirred anymore. With 200 g/L, it was possible to carry out the test however the test item was not fully soluble at this test concentration. Based on these results, the loading rate of 200 g/L was selected as optimal for the main study, because the maximal water solubility of the test item (without pH adjustment) appeared to be > 100 g/L but < 200 g/L.

At this loading rate of 200 g/L and without pH adjustment, 44.4 and 45.5 g Zr/L were measured at 10 and 20 °C, respectively; corresponding to 166 and 169 g test item/L at these two temperatures. The main study also investigated the water solubility at pH = 4 and revealed that no zirconium was detected at this pH.

N.B. Values retained for reporting in the IUCLID field just above and entitled “Water solubility” were thus the following:
- Without pH adjustment: values determined in the main test
- pH = 4: values determined in the main test
- pH = 7: values determined in preliminary experiment 2
- pH = 9: values determined in preliminary experiment 2

Results : without pH adjustment (at 20°C):

Equilibration time	Water solubility at 20 °C: Concentration in g Zr / L
	1^st	2^nd	3^rd	Mean
Day 1	44.9	46.3	45.5	45.6
Day 2	45.4	45.9	45.2	45.5
Day 3	45.2	45.9	44.8	45.3
Overall mean				45.5
Overall standard deviation				0.1

 

Equilibration time	Water solubility at 20 °C: Concentration in g test item / L
	1^st	2^nd	3^rd	Mean
Day 1	167	173	170	170
Day 2	169	171	168	170
Day 3	168	171	167	169
Overall mean				169
Overall standard deviation				1

Results: adjustment to pH 4 (at 20°C):

Equilibration time	Water solubility at 20 °C: Concentration in mg Zr / L
	1^st	2^nd	3^rd	Mean
Day 1	< 0.1	< 0.1	< 0.1	< 0.1
Day 2	< 0.1	< 0.1	< 0.1	< 0.1
Day 3	< 0.1	< 0.1	< 0.1	< 0.1
Overall mean				< 0.1
Overall standard deviation				------

Equilibration time	Water solubility at 20 °C: Concentration in mg test item / L
	1^st	2^nd	3^rd	Mean
Day 1	< 0.4	< 0.4	< 0.4	< 0.4
Day 2	< 0.4	< 0.4	< 0.4	< 0.4
Day 3	< 0.4	< 0.4	< 0.4	< 0.4
Overall mean				< 0.4
Overall standard deviation				------

Results: adjustment to pH 7 (at 20°C):

Equilibrium time	Water solubility at 20 °C: Concentration in mg Zr / L
	1^st	2^nd	3^rd	Mean
Day 1	< 0.012	< 0.012	< 0.012	< 0.012
Day 2	< 0.012	< 0.012	< 0.012	< 0.012
Day 3	< 0.012	< 0.012	< 0.012	< 0.012
Overall mean				< 0.012
Overall standard deviation				------

Equilibrium time	Water solubility at 20 °C: Concentration in mg test item/ L
	1^st	2^nd	3^rd	Mean
Day 1	< 0.05	< 0.05	< 0.05	< 0.05
Day 2	< 0.05	< 0.05	< 0.05	< 0.05
Day 3	< 0.05	< 0.05	< 0.05	< 0.05
Overall mean				< 0.05
Overall standard deviation				---

Results: adjustment to pH 9 (at 20°C):

Equilibrium time	Water solubility at 20 °C: Concentration in mg Zr / L
	1^st	2^nd	3^rd	Mean
Day 1	< 0.012	< 0.012	< 0.012	< 0.012
Day 2	< 0.012	< 0.012	< 0.012	< 0.012
Day 3	< 0.012	< 0.012	< 0.012	< 0.012
Overall mean				< 0.012
Overall standard deviation				------

Equilibrium time	Water solubility at 20 °C: Concentration in mg test item/ L
	1^st	2^nd	3^rd	Mean
Day 1	< 0.05	< 0.05	< 0.05	< 0.05
Day 2	< 0.05	< 0.05	< 0.05	< 0.05
Day 3	< 0.05	< 0.05	< 0.05	< 0.05

Overall mean				< 0.05
Overall standard deviation				------

Conclusions:

The water solubility of the test item (hydrated form of zirconium dinitrate oxide) was determined to be 169 g/L at 20 °C. This maximal water solubility corresponds to a solubility of 115 g/L for anhydrous zirconium dinitrate oxide (substance as registered). Dissolution of the test substance was accompanied with a strong pH decrease of the test solution down to a pH of ca. 0.5. When adjusting pH to 4, 7 or 9, zirconium appears to disappear from the test solution due to precipitation.

Description of key information

The water solubility of zirconium dinitrate oxide (anhydrous) was determined to be 115 g/L at 20°C (corresponding to 169 g test substance/L that is hydrated dinitrate oxide) and pH 0.48 (Bauer, 2015). Dissolution of the substance is accompanied with a strong pH decrease. When adjusting pH to environmentally relevant values (i.e. pH = 4, 7 or 9), no measurable dissolved Zr levels could be observed.

Key value for chemical safety assessment

Water solubility:

115 g/L

at the temperature of:

20 °C

Additional information

A GLP study performed according to OECD guideline 105 and EC Method A.6 (Bauer, 2015) determined the water solubility of the test item to be 169 g/L at 20°C (value calculated based on measurement of 45.5 mg Zr/L by ICP-AES). The nominal loading rate of the test item was 200 g/L. Dissolution of the test substance was clearly accompanied with a pH decrease, as the pH of the test solutions was 0.48. Through recalculation, a water solubility of 115 g/L is obtained for anhydrous zirconium dinitrate oxide.

When adjusting the pH to 4, no dissolved Zr was observed at measurable levels in any of the samples during the main test. No measurements were performed at pH 7 and 9 in the main test, however, during the preliminary tests at a loading rate of 100 g/L (ICP-AES) and 10 g/L (ICP-MS), no measurable dissolved Zr could be observed at these pH levels.