Tantalum

Water solubility

Link to relevant study record(s)

Reference

Reference 1

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)

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:

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: RD21904-10A
- Purity, including information on contaminants, isomers, etc.: Ta 99.9 %
- State of matter and appearance: Powder, grey, black


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.:

9.67 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 filtrates (SD ± 7.33 µg/L)

Key result

Type of test:

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

Mean dissolved conc.:

0.043 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.:

6.46 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 filtrates (SD ± 1.77 µg/L)

Type of test:

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

Mean dissolved conc.:

0.011 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.:

76.2 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 filtrates (SD ± 13.9 µg/L)

Type of test:

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

Mean dissolved conc.:

0.017 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.:

254 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 filtrates (SD ± 62 µg/L)

Type of test:

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

Mean dissolved conc.:

0.002 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 the 2nd full test.:

1 mg/L: 6.46 ± 1.77 µg/L (7 d) and 9.67 ± 7.33 µg/L (28 d)
10 mg/L: 76.2 ± 13.9 µg/L (7 d)
100 mg/L 254 ± 62 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 0.0011 – 0.043 µg/L or below LOQ (estimated to 0.005 µg/L) after background correction.

Conclusions:

The solubility of Ta 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 9.67 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 0.043 µg/L at a loading of 1 mg/L and 28 days.

Executive summary:

The solubility of Ta 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 6.46 ± 1.77 µg/L (7 d) and 9.67 ± 7.33 µg/L (28 d) were measured for 1 mg/L loading, 76.2 ± 13.9 µg/L (7 d) were measured for 10 mg/L loading and 254 ± 62 µg/L (7 d) were measured for 100 mg/L loading.

The Ta concentrations after centrifugal ultra-filtration (3 kDa filtration) were 0.0011 – 0.043 µg/L or below LOQ (estimated to 0.005 µg/L) after background correction.

Reference 2

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

3 August 2012 to 21 August 2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Study conducted 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. The study report was conclusive, done to valid guidelines and the study was conducted under GLP conditions.

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

flask method

Water solubility:

0 g/L

Temp.:

20 °C

Remarks on result:

other: Temperature ± 0.5 ºC

Table 1: Concentration of test material in sample solutions

Sample number	Time shaken at 30 ºC (hours)	Equilibration time at 20 ºC (hours)	Concentration (g/L)	Solution pH
1	24	24	≤ 2.09 x 10^-5	3.0
2	48	24	≤ 2.13 x 10^-5	3.2
3	72	24	≤ 2.07 x 10^-5	6.2

Overall concentration:         ≤ 2.13 × 10^-5 g/L at 20.0 ± 0.5 ºC

Conclusions:

Interpretation of results (migrated information): insoluble (< 0.1 mg/L).
Under the conditions of the study, the water solubility of the test material was determined to be less than or equal to 2.13E-5 g/L at 20.0 ± 0.5 °C. This result classifies the test material as insoluble.

Executive summary:

The water solubility of the test material was determined in accordance with the standardised guidelines EU Method A.6 and OECD 105 using the shake flask method. Under the conditions of the study, the water solubility of the test material was determined to be less than or equal to 2.13 × 10^-5 g/L at 20.0 ± 0.5 °C. This result classifies the test material as insoluble.

Description of key information

The water solubility of the test material was determined in accordance with the standardised guidelines EU Method A.6 and OECD 105 using the shake flask method. Under the conditions of the study, the water solubility of the test material was determined to be less than or equal to 2.13 x 10^-5 g/L at 20.0 ± 0.5 °C.

The ecotoxicologically relevant Ta concentrations dissolved from test specimen after ultra filtration (3 kDa filtration) in a T/D test (OECD 29) were between 0.0011 – 0.043 µg/L or below LOQ (estimated to 0.005 µg/L) after background correction.

These results classify the test material as insoluble.

Key value for chemical safety assessment

Water solubility:

0.043 µg/L

at the temperature of:

21.5 °C