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Physical & Chemical properties

Water solubility

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Reference
Endpoint:
water solubility
Type of information:
experimental study
Adequacy of study:
key study
Study period:
27 November 2017 - 13 February 2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 105 (Water Solubility)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method A.6 (Water Solubility)
Deviations:
no
GLP compliance:
yes (incl. certificate)
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:
< 0.002 mg/L
Conc. based on:
element (dissolved fraction)
Remarks:
tungsten
Temp.:
20 °C
pH:
6
Remarks on result:
other: Expressed as tungsten 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: 0.004 mg Zr/L

Tungsten:
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 W/L
- Limit of detection: 0.002 mg W/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 main tests:

 

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

Solubility expressed as tungsten zirconium hydroxide oxide content in water (mg/L)

Mean pH measured

Temperature (°C)

Test 1

(flow 25 mL/h)

 < 0.02

 -

 6

 20

Test 2

(flow 25 mL/h)

< 0.02

 -  6  20
Mean (Test 1 and Test 2)

< 0.02

 -  6  20

Test 3

(flow 12.5 mL/h)

 < 0.02

 -

 6

 20

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

< 0.02

 < 0.03*  6  20

* The results were extrapolated using the conversation factor e = (Mw (WO3)x(ZrO2)y) / (Mw Zr) = 136/91 = 1.5

The mean solubility in water was reported to be: < 0.02 mg Zr/L at pH 6 and 20°C.

 

Solubility expressed as

tungsten content in water (mg/L)

Solubility expressed as tungsten zirconium hydroxide oxide content in water (mg/L)

Mean pH measured

Temperature (°C)

Test 1

(flow 25 mL/h)

 < 0.002

 -

 6

 20

Test 2

(flow 25 mL/h)

< 0.002

 -  6  20
Mean (Test 1 and Test 2)

< 0.002

 -  6  20

Test 3

(flow 12.5 mL/h)

 < 0.002

 -

 6

 20

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

< 0.002

 < 0.01*  6  20

* The results were extrapolated using the conversation factor e = (Mw (WO3)x(ZrO2)y) / (Mw W) = 136/184 = 0.74

The mean solubility in water was reported to be: < 0.002 mg W/L at pH 6 and 20°C.

Conclusions:
During the water solubility test with tungsten zirconium hydroxide oxide, performed according to the column elution method, the water solubility of the test substance was determined to be < 0.02 mg Zr/L or < 0.002 mg W/L, indicating that the material is highly insoluble in pure water. The test was performed at 20°C and the pH measured during the test was 6.

Description of key information

In the GLP-compliant key study (Buchholz, 2018; Klimisch 1), the water solubility of the test item was determined to be < 0.02 mg Zr/L or < 0.002 mg W/L at pH 6 and 20°C, using the column elution method according to the EU A.6 method and OECD guideline 105.

The material can therefore be concluded to be highly insoluble in pure water.

Key value for chemical safety assessment

Additional information