tungsten zirconium 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:

27 November 2017 - 13 February 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:

< 0.002 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.