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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:
31 October 2017 - 15 March 2018
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:
column elution method
Key result
Water solubility:
< 0.02 mg/L
Conc. based on:
element (dissolved fraction)
Remarks:
zirconium
Temp.:
20 °C
pH:
6
Remarks on result:
other: Expressed as zirconium content in water; mean of flow rates 25 mL/h and 12.5 mL/h.
Key result
Water solubility:
< 0.02 mg/L
Conc. based on:
element (dissolved fraction)
Remarks:
cerium
Temp.:
20 °C
pH:
6
Remarks on result:
other: Expressed as cerium content in water; mean of flow rates 25 mL/h and 12.5 mL/h.
Details on results:
Zirconium:
Results were validated by:
- Linearity validation: The analysis showed a good linearity of the method (r > 0.99).
- Accuracy validation: Results in dilution mixture showed a good accuracy which indicates acceptable data (recoveries ranged between 70 and 110%).
- Repeatability validation: The results indicated a good precision of the data (RSD < 20%).
- Specificity: The intensity (CPS) of blank samples measured was negligible.
- Limit of quantification: 0.02 mg Zr/L
- Limit of detection: 0.01 mg Zr/L

Cerium:
Results were validated by:
- Linearity validation: The analysis showed a good linearity of the method (r > 0.99).
- Accuracy validation: Results in dilution mixture showed a good accuracy which indicates acceptable data (recoveries ranged between 70 and 110%).
- Repeatability validation: The results indicated a good precision of the data (RSD < 20%).
- Specificity: The intensity (CPS) of blank samples measured was negligible.
- Limit of quantification: 0.02 mg Ce/L
- Limit of detection: 0.01 mg Ce/L

Results of the preliminary test with milliQ water at pH 6 were:

Amount of test item weighed (g)  0.1  0.1  0.1  0.1  0.1 0.1   0.01
 Volume of water added (mL) 0.1  0.5  1 2  10 100  1000
 Solubility (yes/no)  No No  No  No  No  No  No (after > 96 h of agitation of the test solution)

Results of the preliminary test with milliQ water at pH 4 were:

Amount of test item weighed (g)  0.1  0.1  0.1  0.1  0.1 0.1   0.01
 Volume of water added (mL) 0.1  0.5  1 2  10 100  1000
 Solubility (yes/no)  No No  No  No  No  No  No (after > 96 h of agitation of the test solution)

Results of the preliminary test with milliQ water at pH 7 were:

Amount of test item weighed (g)  0.1  0.1  0.1  0.1  0.1 0.1   0.01
 Volume of water added (mL) 0.1  0.5  1 2  10 100  1000
 Solubility (yes/no)  No No  No  No  No  No  No (after > 96 h of agitation of the test solution)

Results of the preliminary test with milliQ water at pH 9 were:

Amount of test item weighed (g)  0.1  0.1  0.1  0.1  0.1 0.1   0.01
 Volume of water added (mL) 0.1  0.5  1 2  10 100  1000
 Solubility (yes/no)  No No  No  No  No  No  No (after > 96 h of agitation of the test solution)

Results of the main test:

 

Solubility expressed as

Zirconium content in water (mg/L)

Solubility expressed as Cerium content in water (mg/L)

Mean pH measured

Temperature (°C)

Test 1

(flow 25 mL/h)

 < 0.02

 < 0.02

 6

 20

Test 2

(flow 25 mL/h)

< 0.02

 < 0.02  6  20
Mean (Test 1 and Test 2)

< 0.02

 < 0.02  6  20

Test 3

(flow 12.5 mL/h)

 < 0.02

 < 0.02

 6

 20

Mean (12.5 mL/h and 25 mL/h)

< 0.02

 < 0.02  6  20
Conclusions:
During the water solubility test with the reaction mass of cerium dioxide, praseodymium oxide and zirconium dioxide, performed according to the column elution method, the water solubility of zirconium and cerium from the test substance was determined to be < 0.02 mg/L for both elements, indicating that the material is highly insoluble. The test was performed at 20°C and the average pH measured during the test was 6.

Description of key information

In the GLP-compliant guideline study (Buchholz, 2018; Klimisch 1) within which the solubility in water of one batch of the reaction mass of cerium dioxide, praseodymium oxide and zirconium dioxide was determined according to the EU A.6 method and OECD guideline 105, the mean solubility in water was determined to be < 0.02 mg/L at pH 6 and 20°C for both zirconium and cerium, according to the column elution method. The material can therefore be concluded to be highly insoluble.

Key value for chemical safety assessment

Additional information