Ditantalum pentaoxide

Water solubility

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

20 June 2012 - 7 August 2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study conducted to GLP in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results.

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

Type of method:

flask method

Water solubility:

< 0.005 mg/L

Temp.:

20 °C

pH:

6.2 - 7

Remarks on result:

other: Replicates of 5 days

Water solubility:

< 0.005 mg/L

Temp.:

10 °C

pH:

7.1 - 8.1

Remarks on result:

other: Replicates of 5 days

Details on results:

Preliminary test
The preliminary water solubility of the test material was < 0.005 mg/L at 20.0 °C.

Definitive test
The difference between the concentrations of the test material on day 1 to 5 at 10 and 20 °C was < 15 % and the concentrations showed no relevant tendency. Therefore the mean of day 1 - 5 was taken as the solubility at both temperatures, according to the guidelines.

Table 1 Water Solubility at 10 °C

The mass concentration of the test material was determined at different time points after initiation of stirring. Two solutions were used.

Equilibration Time (days)	pH of the Solutions		Concentration (mg/L)			Deviation from the Maximum Concentration (%)
	1st	2nd	1st	2nd	Mean
1	7.9	8.0	<0.005	<0.005	<0.005	0.0
2	8.1	7.8	<0.005	<0.005	<0.005	0.0
3	8.1	7.7	<0.005	<0.005	<0.005	0.0
4	7.5	7.2	<0.005	<0.005	<0.005	0.0
5	7.5	7.1	<0.005	<0.005	<0.005	0.0

Mean (day 1 - 5) = <0.005 mg/L

 

Table 2 Water Solubility at 20 °C

The mass concentration of the test material was determined at different time points after initiation of stirring. Two solutions were used.

Equilibration Time (days)	pH of the Solutions		Concentration (mg/L)			Deviation from the Maximum Concentration (%)
	1st	2nd	1st	2nd	Mean
1	7.0	6.9	<0.005	<0.005	<0.005	0.0
2	6.9	6.7	<0.005	<0.005	<0.005	0.0
3	6.2	6.3	<0.005	<0.005	<0.005	0.0
4	6.9	6.5	<0.005	<0.005	<0.005	0.0
5	6.9	6.5	<0.005	<0.005	<0.005	0.0

Mean (day 1 - 5) = <0.005 mg/L

Conclusions:

Interpretation of results (migrated information): insoluble (< 0.1 mg/L)
The solubility of the test material was determined to be <0.005 mg/L, as a mean value over 5 days at 20 °C. Therefore under the conditions of this study, the test material is insoluble.

Executive summary:

The water solubility of the test material was determined in accordance with the standardised guidelines OECD 105 and EU Method A.6.

The flask shaking test was performed as the test material is inorganic and the column elution method is not recommended for this type of material.

The water solubility was investigated at 10 and 20 °C and in both cases was found to be <0.005 mg/L.

Under the conditions of this study, the test material was found to have a water solubility of <0.005 mg/L in purified water at both 10 and 20 °C. It can therefore be described as insoluble.

Reference 2

Endpoint:

transformation / dissolution of metals and inorganic metal compounds

Type of information:

experimental study

Adequacy of study:

key study

Study period:

#

Reliability:

1 (reliable without restriction)

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

other: test was conducted in vessels in accordance with the OECD guideline 29.

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source (i.e. manufacturer or supplier) and lot/batch number of test material: Taniobis GmbH, Im Schleeke 78 - 91, 38642 Goslar, Deutschland; Batch: 190310
- Purity, including information on contaminants, isomers, etc.: Ta2O5 99.9 %
- State of matter and appearance: Powder white


STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Store dry in tightly closed container. Store away from heat/sparks/open flame/hot surfaces.
- Stability in the medium, i.e. sensitivity of the test material to hydrolysis and/or photolysis: stable (samples were acidified for stabilization)
- Solubility and stability of the test material in the solvent/vehicle and the exposure medium: stable (samples were acidified for stabilization)
- Reactivity of the test material with the incubation material used (e.g. plastic ware): none

Type of test:

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

Mean dissolved conc.:

1 µg/L

Element analysed:

Ta

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

pH 6.0

Remarks on result:

other: 0.2 µm filtrate (SD ± 0.21 µg/L)

Type of test:

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

Mean dissolved conc.:

0.018 µg/L

Element analysed:

Ta

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

pH 6.0

Remarks on result:

other: centrifugally ultra-filtered

Type of test:

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

Mean dissolved conc.:

0.314 µg/L

Element analysed:

Ta

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

pH 6.0

Remarks on result:

other: 0.2 µm filtrate (SD ± 0.280 µg/L)

Type of test:

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

Mean dissolved conc.:

0.012 µg/L

Element analysed:

Ta

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

pH 6.0

Remarks on result:

other: centrifugally ultra-filtered

Type of test:

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

Mean dissolved conc.:

4.44 µg/L

Element analysed:

Ta

Loading of aqueous phase:

10 mg/L

Incubation duration:

7 d

Test conditions:

pH 6.0

Remarks on result:

other: 0.2 µm filtrate (SD ± 3.46 µg/L)

Type of test:

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

Mean dissolved conc.:

0.014 µg/L

Element analysed:

Ta

Loading of aqueous phase:

10 mg/L

Incubation duration:

7 d

Test conditions:

pH 6.0

Remarks on result:

other: centrifugally ultra-filtered

Type of test:

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

Mean dissolved conc.:

311 µg/L

Element analysed:

Ta

Loading of aqueous phase:

100 mg/L

Incubation duration:

7 d

Test conditions:

pH 6.0

Remarks on result:

other: 0.2 µm filtrate (SD ± 51 µg/L)

Key result

Type of test:

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

Mean dissolved conc.:

0.16 µg/L

Element analysed:

Ta

Loading of aqueous phase:

100 mg/L

Incubation duration:

7 d

Test conditions:

pH 6.0

Remarks on result:

other: centrifugally ultra-filtered

Details on results:

In 0.2 µm filtrates the following Ta concentrations were measured in 2nd test.:

1 mg/L: 0.314 ± 0.280 µg/L (7 d) and 1.00 ± 0.21 µg/L (28 d)
10 mg/L: 4.44 ± 3.46 µg/L (7 d)
100 mg/L 311 ± 51 µg/L (7 d)

It may be assumed that the amount of tantalum in 0.2 µm filtrates originate from colloidal / particulate / suspended species whereas almost no truly dissolved species can be found after centrifugal ultra-filtration.

For the loading of 1 mg/L background correction was applied because measured Ta concentrations in method blanks were low but in the range of the quantified amount in test item loaded samples.
The Ta concentrations after centrifugal ultra-filtration were 0.012 – 0.160 µg/L after background correction.

Conclusions:

The solubility of Ta2O5 was tested in a 7- and 28-day T/D test according to the OECD guideline 29. The highest concentration measured after 28 d was 1 µg/L (mean) resulting from a loading of 1 mg/L Ta at pH 6 (based on 0.2 µm filtrates).
However, it may be assumed that the amount of tantalum in 0.2 µm filtrates originate from colloidal / particulate / suspended species whereas almost no truly dissolved species can be found after centrifugal ultra-filtration.
After 0.2 µm filtration and centrifugal ultra-filtration (3 kDa filtration), the highest Ta concentration was 0.16 µg/L at a loading of 100 mg/L and 7 days.

Executive summary:

The solubility of Ta2O5 was tested in a screening test (1-day) and a full 7- and 28-day T/D test at pH 6 according to the OECD guideline 29 (loading 1, 10 and 100 mg/L). The concentrations of Ta was quantified via gas chromatography (ICP-MS). Concentrations were corrected with background concentrations of the water blanks. Before chemical analysis water samples were filtrated through 0.2 µm and 3 kDa filters. 

In 0.2 µm filtrates mean Ta concentrations of 1.00 ± 0.21 µg/L (7 d) and 0.314 ± 0.280 µg/L (28 d) were measured for 1 mg/L loading, 4.44 ± 3.46 µg/L (7 d) were measured for 10 mg/L loading and 311 ± 51 µg/L (7 d) were measured for 100 mg/L loading.

The Ta concentrations after centrifugal ultra-filtration (3 kDa filtration) were 0.012 – 0.160 µg/L after background correction.

Description of key information

The water solubility of the test material was determined to be < 0.005 mg/L at 20 °C in the key study. 

The ecotoxicologically relevant Ta concentrations dissolved from test specimen after ultra filtration (3 kDa filtration) in a T/D test (OECD 29) were between were 0.012 – 0.160 µg/L after background correction

These results classify the test material as insoluble.

Key value for chemical safety assessment

Water solubility:

0.16 µg/L

at the temperature of:

21.5 °C

Additional information

The water solubility of the test material has been addressed by providing a key study in the form of a test report (Wenighofer and Fröschl, 2012) that was assigned a reliability score of 1, using the principles set out in Klimisch (1997). The water solubility was investigated in accordance with the standardised guidelines OECD 105 and EU method A.6 using the flask shaking method.

Under the conditions of this study, the test material was found to have a water solubility of < 0.005 mg/L in purified water at both 10 and 20 °C. It can therefore be described as insoluble.

Supporting information is provided in the form of a company report (Sunderkötter, 2012) that was assigned a reliability score of 2, using the principles set out in Klimisch (1997). The water solubility was investigated in accordance with the standardised guidelines OECD 105 and EU Method A.6. The mean solubility in water at 30.0 °C (loading rate 20 g/L, pH 6.2–6.6) is < 1 mg/L.

Further supporting information is provided in the form of handbook data. All three sources are peer reviewed data that, as such, can be awarded a reliability score of 2 in accordance with the criteria detailed in Klimisch (1997). 

Kirk (1997), Clayton (1981) and O’Neil (2006) all quoted the test material as being insoluble. No specific value for the solubility was provided and methods of determination are not included in handbook data.

In the test conducted by Klawonn (2022), the ecotoxicologically relevant Ta concentrations dissolved from test specimen after ultra filtration (3 kDa filtration) in the T/D test (OECD 29) were between were 0.012 – 0.160 µg/L after background correction.