Tungsten disulphide

Water solubility

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Other quality assurance:

ISO/IEC 17025 (General requirements for the competence of testing and calibration laboratories)

Type of method:

flask method

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: International Tungsten Association Batch No.: S 606078

Key result

Water solubility:

ca. 1.76 mg/L

Conc. based on:

test mat. (total fraction)

Loading of aqueous phase:

100 mg/L

Incubation duration:

ca. 6 d

Temp.:

20 °C

pH:

>= 5.3 - <= 5.9

Key result

Water solubility:

ca. 18 mg/L

Conc. based on:

test mat. (total fraction)

Loading of aqueous phase:

1 000 mg/L

Incubation duration:

ca. 4 d

Temp.:

20 °C

pH:

>= 6 - <= 6.1

Conclusions:

Results: Water Solubility according to OECD-Guideline 105 of the test item Tungsten Disulfide of International Tungsten Association was investigated by Inductively Coupled Plasma - Mass Spectrometry (ICP-MS) of the mass of the test item in the solute after filtration with reference to the Tungstenmoiety of the test item.
Water Solubility of the test item Tungsten Disulfide at nominal test concentration of 100 mg Tungsten Disulfide/L: 1.76 mg/L
Water Solubility of the test item Tungsten Disulfide at nominal test concentration of 1.000 mg Tungsten Disulfide/L: 18 mg/L

Executive summary:

Results of ICP-MS-analysis (ICP-MS = Inductively Coupled Plasma - Mass Spectrometry) of the Definitive Water Solubility Test with Tungsten Disulfide at nominal test concentrations of 100 and 1.000 mg Tungsten Disulfide/L increased with nominal concentrations. During the testing period of 5 days a continuous increase could be observed at both nominal concentrations, hence a plateau phase, as recommended by OECD-Guideline 105 with reference to validity criteria, could not be confirmed for Tungsten Disulfide in the Definitive Water Solubility Test. This finding is obviously caused by chemical reactions under the aerobic conditions of the Definitive Water Solubility Test with Tungsten Disulfide, where an oxidation can be achieved by oxygen and further equilibria may be involved according to the equations: 

WS₂+ 0.5 O₂+ H₂Oà2H⁺+ WS₂O₂^2-WS₂O₂^2-+ H₂OßàWSO₃^2-+ H₂S WSO₃^2-+ H₂OßàWSO₄^2-+ H₂S.

Therefore, it was decided, that it is not feasible to apply the validity criteria of OECD-Guideline 105 and to give both results of the Definitive Water Solubility Test with Tungsten Disulfide at nominal test concentrations of 100 and 1.000 mg Tungsten Disulfide/L

Reference 2

Endpoint:

transformation / dissolution of metals and inorganic metal compounds

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2016-11-21, 2016-12-05

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Series on Testing and Assessment No. 29 (23-Jul-2001): Guidance document on transformation/dissolution of metals and metal compounds in aqueous media

GLP compliance:

yes (incl. QA statement)

Type of method:

flask method

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: Tribotecc Gmbtt in Austria
- Expiration date of the lot/batch:
- Purity test date:95%


STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material:
- Stability under test conditions:
- Solubility and stability of the test substance in the solvent/vehicle:
- Reactivity of the test substance with the solvent/vehicle of the cell culture medium:

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
To achieve pH levels of 6 and 8.5, a modified composition of the standard OECD 203 aquatic testing medium for fish and Daphnia was used.

FORM AS APPLIED IN THE TEST (if different from that of starting material)

OTHER SPECIFICS:

Key result

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

<= 0.1 µg/L

Element analysed:

total tungsten

Loading of aqueous phase:

100 mg/L

Incubation duration:

0 h

Test conditions:

pH 6

Key result

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

<= 0.13 µg/L

Element analysed:

tungstate ion

Loading of aqueous phase:

100 mg/L

Incubation duration:

0 h

Test conditions:

pH6

Key result

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

ca. 209.1 µg/L

Element analysed:

Total Tungsten

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

pH6

Key result

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

ca. 297.9 µg/L

Element analysed:

tungstate ion

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

pH 6

Key result

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

<= 0.24 µg/L

Element analysed:

Total Tungsten

Loading of aqueous phase:

100 mg/L

Incubation duration:

0 h

Test conditions:

pH 8.5

Key result

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

<= 0.29 µg/L

Element analysed:

tungstate ion

Loading of aqueous phase:

100 mg/L

Incubation duration:

0 h

Test conditions:

pH8.5

Key result

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

ca. 473.7 µg/L

Element analysed:

total tungsten

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

pH 8.5

Key result

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

ca. 730.1 µg/L

Element analysed:

tungstate ion

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

pH8.5

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

ca. 5 µg/L

Element analysed:

Total Tungsten

Loading of aqueous phase:

1 mg/L

Incubation duration:

0

Test conditions:

pH8.5

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

ca. 32 µg/L

Element analysed:

total tungsten

Loading of aqueous phase:

1 mg/L

Incubation duration:

168 h

Test conditions:

pH 8.5

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

44 µg/L

Element analysed:

tungstate ion

Loading of aqueous phase:

1 mg/L

Incubation duration:

168 h

Test conditions:

pH 8.5

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

40 µg/L

Element analysed:

total tungsten

Loading of aqueous phase:

1 mg/L

Incubation duration:

336 h

Test conditions:

pH 8.5

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

ca. 46 µg/L

Element analysed:

tungstate ion

Loading of aqueous phase:

1 mg/L

Incubation duration:

336 h

Test conditions:

pH 8.5

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

ca. 40 µg/L

Element analysed:

total tungsten

Loading of aqueous phase:

1 mg/L

Incubation duration:

672 h

Test conditions:

pH 8.5

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

ca. 49 µg/L

Element analysed:

tungstate ion

Loading of aqueous phase:

1 mg/L

Incubation duration:

672 h

Test conditions:

pH 8.5

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

ca. 186 µg/L

Element analysed:

total tungsten

Loading of aqueous phase:

10 mg/L

Incubation duration:

168 h

Test conditions:

pH 8.5

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

ca. 246 µg/L

Element analysed:

tungstate ion

Loading of aqueous phase:

10 mg/L

Incubation duration:

168 h

Test conditions:

pH 8.5

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

ca. 2 439 µg/L

Element analysed:

total tungsten

Loading of aqueous phase:

100 mg/L

Incubation duration:

168 h

Test conditions:

pH 8.5

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

ca. 3 606 µg/L

Element analysed:

tungstate ion

Loading of aqueous phase:

100 mg/L

Incubation duration:

168 h

Test conditions:

pH 8.5

Conclusions:

The dissolve tungsten concentrations for both the 10 and 100 mg/L loadings represent about 3% dissolution of the tungsten disulphide. From all the tungstate speciation results, it can be assumed that WO4 is the predominant anion in solution.

Executive summary:

Using the UN Transformation/Dissolution Protocol (T/DP) for metals and sparingly soluble metal compounds, the concentrations of total dissolved W and of the WO4 anion were measured to examine the T/D behaviour of powder form tungsten disulphide. The analyses of the T/D solutions were conducted for total dissolved W and for the WO4 anion, each analyte being independent of the other. The parameter y, defined as [W]/[ WO4 ] and based on molecule weights, was used and would have a value of 0.742 if all dissolved W were in solution as the WO4  anion.

From the scoping tests at pH 6 and 8.5, an effect of pH on the reactivity of the tungsten disulphide was observed. At pH 6, the 100 mg/L loadings reacted and dissolved to yield 210g/L (σ% = 10) and 298 g/L (σ% = 10) of W and WO4 , respectively. However, at pH 8.5, the corresponding concentrations are 474 ug/L (σ% = 6) and 730 ug/L (σ% = 7). Y values at pH 6 and 8.5 are 0.702 and 0.671 respectively, indicating that tungstate is the predominant anion in solution. Based on these results, the definitive 7- and 28-day tests were conducted at pH 8.5

At 168 hr, the net average concentrations of both total dissolved W and the WO4 species for the 1 mg/L loadings are 32 ug/L (σ% = 28) and 44 ug/L (σ% = 32), respectively, corresponding to about 4% of the potential W and WO4 release from the tungsten disulphide. Over the 672 hr,  the average value of y is 0.765, which compares favourably with the calculated value of 0.742. For the 10 mg/L loadings, the 168 hr values of W and WO4  are 186 ug/L (σ% = 12) and 246ug/L (σ% = 12), respectively, with an attendant y value of 0.756.  For the 100 mg/L loadings,    W and WO4 are 2,439 ug/L (σ% = 9) and 3,606 ug/L (σ% = 9), respectively, at 168 hr and y is 0.676, which is within the lower boundary of the 5% r.a. range. The W concentrations for both the 10 and 100 mg/L loadings represent about 3% dissolution of the tungsten disulphide. From all the tungstate speciation results, it can be assumed that WO4 is the predominant anion in solution.

Based on the T/D reaction kinetic data and the acute ERV of 31 mg/L and the chronic ERV of 3.37 mg/L (Clements et al., 2012), the tungsten disulphide would not classify under either the UN GHS scheme or the EU CLP hazard classification scheme.

Description of key information

Tungsten disulphide (OECD-Guideline 105) at nominal test concentration of 100 mg tungsten disulphide/L: 1.76 mg of W/L; at nominal test concentration of 1000 mg tungsten disulphide/L: 18 mg of W/L.

Tungsten disulphide in the transformation dissolution protocol, the tungsten concentrations for both the 10 and 100 mg/L loadings represent about 3% dissolution of the tungsten disulphide. From all the tungstate speciation results, it can be assumed that tungstate is the predominant anion in solution.

Key value for chemical safety assessment

Water solubility:

18 mg/L

at the temperature of:

20 °C