Registration Dossier
Registration Dossier
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EC number: 231-113-5 | CAS number: 7440-03-1
Water solubility
Administrative data
Link to relevant study record(s)
- Endpoint:
- water solubility
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- other: GLP-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
- Deviations:
- no
- GLP compliance:
- yes (incl. QA statement)
- Type of method:
- other: Transformation/Dissolution test
- Water solubility:
- < 0.01 µg/L
- Temp.:
- 21
- pH:
- 8
- Remarks on result:
- other: Concentration of Nb at loading rate 1mg/L (test item) in the short term test after 7 days.
- Water solubility:
- < 0.01 µg/L
- Temp.:
- 21
- pH:
- 8
- Remarks on result:
- other: Concentration of Nb at loading rate 10 mg/L (test item) in the short term test after 7 days.
- Water solubility:
- 0.104 µg/L
- Temp.:
- 21 °C
- pH:
- 8
- Remarks on result:
- other: Concentration of Nb at loading rate 100 mg/L (test item) in the short term test after 7 days.
- Water solubility:
- < 0.01 µg/L
- Temp.:
- 21.3
- pH:
- 8
- Remarks on result:
- other: Concentration of Nb at loading rate 1mg/L (test item) in the long term test after 28 days.
- Details on results:
- Short term test:
The results indicates an increasing solubility until 0.104 µg/L Nb after 7 days (100 mg/L loading). The solubility of the two loadings of 1 mg/L Nb and 10 mg/L Nb are below 0.01 µg/L.
Long term test:
During the 28 day solubility test with 1 mg/L Niobium Metal, the determined concentrations didn't exceed 0.01 µg/L for all taken samples. Thus, it is considered to be justified that the solubility of Niobium Metal in water is < 0.01 µg/L. - Endpoint:
- water solubility
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 9 Nov - 20 Dec 2010
- Reliability:
- 2 (reliable with restrictions)
- 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)
- Remarks:
- Landesanstalt für Umwelt, Messungen und Naturschutz Baden-Württemberg, Karlsruhe, Germany
- Type of method:
- other: Transformation/Dissolution test
- Water solubility:
- < 4.5 µg/L
- Temp.:
- 21.5 °C
- pH:
- 5.5
- Remarks on result:
- other: Fe after 28 d and 1 mg/L loading
- Water solubility:
- < 0.045 µg/L
- Temp.:
- 21.5 °C
- pH:
- 5.5
- Remarks on result:
- other: Nb after 28 d and 1 mg/L loading
- Water solubility:
- < 15 µg/L
- Temp.:
- 21.4 °C
- pH:
- 6
- Remarks on result:
- other: Fe after 7 d and 100 mg/L loading
- Water solubility:
- < 0.15 µg/L
- Temp.:
- 21.4 °C
- pH:
- 6
- Remarks on result:
- other: Nb after 7 d and 100 mg/L loading
- Endpoint:
- transformation / dissolution of metals and inorganic metal compounds
- 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 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: OECD Series No 29
- Type of test:
- screening transformation/dissolution test - sparingly soluble metal compounds
- Mean dissolved conc.:
- < 15 µg/L
- Element analysed:
- Fe
- Loading of aqueous phase:
- 100 mg/L
- Incubation duration:
- 24 h
- Test conditions:
- buffer solution at pH 5.5
- Remarks on result:
- other: LOQ: 15 µg/L
- Remarks:
- The determined dissolved iron concentration in five test vessels with two samples each did not exceed
- Type of test:
- full transformation/dissolution test - metals and sparingly soluble metal compounds
- Mean dissolved conc.:
- 23.8 µg/L
- Element analysed:
- Fe
- Loading of aqueous phase:
- 100 mg/L
- Incubation duration:
- 7 d
- Test conditions:
- buffer solution at pH 5.5
- Remarks on result:
- other: range: 20.7 µg/L - 27.1 µg/L mean value: 23.8 ± 12.7%
- Remarks:
- The seven day short term test for iron was performed with loadings of 1, 10 and 100 mg test item per litre at pH 5.5. For the loading rates 1 mg/L and 10 mg/L the measured Fe concentrations have been determined to be below the limit of quantification (LOQ 15 µg/L) and have not be detected (LOD 4.04 µg/L)
- Type of test:
- full transformation/dissolution test - metals and sparingly soluble metal compounds
- Mean dissolved conc.:
- < 4.04 µg/L
- Element analysed:
- Fe
- Loading of aqueous phase:
- 10 mg/L
- Incubation duration:
- 7 h
- Test conditions:
- buffer solution at pH 5.5
- Remarks on result:
- other: Fe was not detected (< 4.04 µg/L Fe)
- Type of test:
- full transformation/dissolution test - metals and sparingly soluble metal compounds
- Mean dissolved conc.:
- < 4.04 µg/L
- Element analysed:
- Fe
- Loading of aqueous phase:
- 1 mg/L
- Incubation duration:
- 7 d
- Test conditions:
- buffer solution at pH 5.5
- Remarks on result:
- other: Fe was not detected (< 4.04 µg/L Fe)
- Type of test:
- full transformation/dissolution test - metals and sparingly soluble metal compounds
- Mean dissolved conc.:
- < 4.04 µg/L
- Element analysed:
- Fe
- Loading of aqueous phase:
- 1 mg/L
- Incubation duration:
- 28 d
- Test conditions:
- buffer solution at pH 5.5
- Remarks on result:
- other: Fe was not detected (< 4.04 µg/L Fe)
- Type of test:
- screening transformation/dissolution test - sparingly soluble metal compounds
- Mean dissolved conc.:
- 0.656 µg/L
- Element analysed:
- Nb
- Loading of aqueous phase:
- 100 mg/L
- Incubation duration:
- 24 h
- Test conditions:
- buffer solution at pH 8.5
- Remarks on result:
- other: The determined dissolved niobium concentration in five test vessels with two samples each did not exceed 1.06 µg/L niobium for all taken samples. The mean niobium concentration in the screening test was found to be 0.656 µg/L at 20 °C.
- Type of test:
- full transformation/dissolution test - metals and sparingly soluble metal compounds
- Mean dissolved conc.:
- 2.97 µg/L
- Element analysed:
- Nb
- Loading of aqueous phase:
- 100 mg/L
- Incubation duration:
- 7 d
- Test conditions:
- buffer solution at pH 8.5
- Remarks on result:
- other: range: 2.26 µg/L - 3.80 µg/L mean value: 2.97 ± 23.0%
- Type of test:
- full transformation/dissolution test - metals and sparingly soluble metal compounds
- Mean dissolved conc.:
- 1.47 µg/L
- Element analysed:
- Nb
- Loading of aqueous phase:
- 10 mg/L
- Incubation duration:
- 7 d
- Test conditions:
- buffer solution at pH 8.5
- Remarks on result:
- other: range: 1.36 µg/L - 1.62 µg/L mean value: 1.47 ± 7.80
- Type of test:
- full transformation/dissolution test - metals and sparingly soluble metal compounds
- Mean dissolved conc.:
- < 0.15 µg/L
- Element analysed:
- Nb
- Loading of aqueous phase:
- 1 mg/L
- Incubation duration:
- 7 d
- Test conditions:
- buffer solution at pH 8.5
- Remarks on result:
- other: LOQ Nb: 0.150 µg/L
- Type of test:
- full transformation/dissolution test - metals and sparingly soluble metal compounds
- Mean dissolved conc.:
- 0.302 µg/L
- Element analysed:
- Nb
- Loading of aqueous phase:
- 1 mg/L
- Incubation duration:
- 28 d
- Test conditions:
- buffer solution at pH 8.5
- Remarks on result:
- other: range: <150 µg/L - 0.540 µg/L
- Details on results:
- All tests were performed an room temperature in the range of 21 - 23°C
A preliminary test for finding the pH maximising transformation/dissolution was not performed because this information is already confirmed for niobium and iron.
With a buffer solution at pH 5.5 a screening transformation/dissolution test was performed for iron with a test item load of 100 mg per litre for a duration of 24 hours. The determined dissolved iron concentration in five test vessels with two samples each did not exceed <LOQ (12.1 µg/L) iron for all taken samples. The mean iron concentration in the screening test was found to be <LOQ (9.13 µg/L) and the mean temperature in this test was 20 °C (minimum temperature: 20 °C and maximum temperature: 21 °C).
The seven day short term test for iron was performed with loadings of 1, 10 and 100 mg test item per litre at pH 5.5. The concentration after 7 days did not exceed 27.1 µg/L (determined after 168 hours of shaking, 100 mg/L of test item) iron for all taken samples. For short term test the mean iron concentration for a test item load of 100 mg/L was found to be 23.8 µg/L (shaking time of 168 hours). For all other test item loading no iron was detectable. The mean temperature for this test was 20 °C (minimum temperature: 19 °C and maximum temperature: 21 °C).
The 28 day long term test for iron was performed with 1 mg test item per litre at pH 5.5. No iron was detectable after 28 days for all taken samples (limit of detection: 4.04 µg/L iron). The mean temperature for this test was 20 °C (minimum temperature: 19 °C and maximum temperature: 21 °C).
Screening transformation/dissolution test for niobium was prepared in a buffer solution at pH 8.5 with a test item load of 100 mg per litre for a duration of 24 hours. The determined dissolved niobium concentration in five test vessels with two samples each did not exceed 1.06 µg/L niobium for all taken samples. The mean niobium concentration in the screening test was found to be 0.656 µg/L and the mean temperature in this test was 20 °C (minimum temperature: 20 °C and maximum temperature: 21 °C).
The seven day short term test for niobium was performed with loadings of 1, 10 and 100 mg test item per litre at pH 8.5. The concentration after 7 days did not exceed 3.80 µg/L (determined after 168 hours of shaking, 100 mg/L of test item) iron for all taken samples. For short term test the mean niobium concentration for a test item load of 100 mg/L was found to be 2.97 µg/L (at shaking time of 168 hours) and mean niobium concentration for test item load at 10 mg/L was found to be 1.47 µg/L at shaking time of 168 hours. For a test item load of 1 mg/L no niobium was detectable. The mean temperature for this test was 20 °C (minimum temperature: 20 °C and maximum temperature: 21 °C).
The 28 day long term test for niobium was performed with 1 mg test item per litre at pH 8.5. The concentration after 28 days did not exceed 0.545 µg/L niobium for all taken samples. The mean niobium concentration in the long term test was found to be 0.302 µg/L and the mean temperature in this test was 20 °C (minimum temperature: 19 °C and maximum temperature: 21 °C).
- Endpoint:
- water solubility
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 2009-07-23 to 2009-09-01
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- other: Guideline study
- 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:
- < 0.5 µg/L
- Temp.:
- 20 °C
- pH:
- 6
- Details on results:
- The solubility of the test item in water at 20°C is below the LOQ, which is 0.5 µg/L. The pH value is 6.0.
- Conclusions:
- Interpretation of results (migrated information): insoluble (< 0.1 mg/L)
Based on the study results the test item is considered to be insoluble in water at 20°C. - Endpoint:
- water solubility
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 2009-09-02 to 2009-09-22
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- other: Guideline study
- 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:
- 0.8 µg/L
- Temp.:
- 20
- pH:
- 6.2
- Remarks on result:
- other: Result refers to the niobium content
- Water solubility:
- ca. 1 µg/L
- Temp.:
- 20 °C
- pH:
- 6.2
- Remarks on result:
- other: Result refers to the Alloy (FeNb)
- Details on results:
- Results:
Blank values
Niobium content (mean value): < 0.5 μg/l
Iron content (mean value): < 10 μg/l
Water solubility at 20 °C (first determination)
Water solubility at 20 °C
Niobium content (mean value): 64 μg/l (97 μg/l Alloy)
Iron content (mean value): Not calculated because of low reproducibility
pH-value: 6.2
Water solubility at 20 °C (after filtration and centrufigation)
Niobium content (mean value): 0.8 μg/l (1 μg/l Alloy)
Iron content (mean value): <10 μg/l - Conclusions:
- The water solubility of the alloy Ferro niobium is approx. 1 μg/l.
- Endpoint:
- water solubility
- Type of information:
- experimental study
- Adequacy of study:
- supporting study
- Study period:
- 2010-06-22 to 2010-07-08
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- other: GLP-Guideline study. Only short term test (7 days) was experimentally performed.
- Qualifier:
- according to guideline
- Guideline:
- other: OECD guideline 29
- Deviations:
- yes
- Remarks:
- : Only the short term test was experimentally performed.
- GLP compliance:
- yes (incl. QA statement)
- Type of method:
- other: Guidance document o transformation/dissolution of metals and metal compounds in aqueous media
- Water solubility:
- < 0.5 µg/L
- Temp.:
- 21 °C
- pH:
- 8
- Remarks on result:
- other: after 7 days
- Conclusions:
- Interpretation of results (migrated information): insoluble (< 0.1 mg/L)
Based on the study results the test item is considered to be insoluble in water at 21°C (pH 8). - Endpoint:
- transformation / dissolution of metals and inorganic metal compounds
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- guideline study with acceptable restrictions
- 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: OECD Series No 29
- Type of test:
- full transformation/dissolution test - metals and sparingly soluble metal compounds
- Mean dissolved conc.:
- < 0.4 µg/L
- Element analysed:
- Nb
- Loading of aqueous phase:
- 10 mg/L
- Incubation duration:
- 7 d
- Test conditions:
- pH 8
- Remarks on result:
- other: at 20.8 °C
- Remarks:
- Nb LOD: 0.4 µg/L
- Type of test:
- full transformation/dissolution test - metals and sparingly soluble metal compounds
- Mean dissolved conc.:
- 2.77 µg/L
- Element analysed:
- Nb
- Loading of aqueous phase:
- 100 mg/L
- Incubation duration:
- 7 d
- Test conditions:
- pH 8
- Remarks on result:
- other: at 20.8 °C
- Remarks:
- 2.77±12.3
- Type of test:
- full transformation/dissolution test - metals and sparingly soluble metal compounds
- Mean dissolved conc.:
- 3.5 µg/L
- Element analysed:
- Nb
- Loading of aqueous phase:
- 1 000 mg/L
- Incubation duration:
- 7 d
- Test conditions:
- pH 8
- Remarks on result:
- other: at 20.8 °C
- Remarks:
- 3.50 ± 12.0
- Type of test:
- full transformation/dissolution test - metals and sparingly soluble metal compounds
- Mean dissolved conc.:
- < 0.4 µg/L
- Element analysed:
- Nb
- Loading of aqueous phase:
- 10 mg/L
- Incubation duration:
- 28 d
- Test conditions:
- pH 8
- Remarks on result:
- other: at 20.5 °C
- Remarks:
- Nb LOD: 0.4 µg/L
- Details on results:
- During the 7 days solubility test with Niobium (powder form), the determined concentrations did not exceed 3.97 pg/L niobium for all taken samples.
Referenceopen allclose all
Preliminary test:
pH planned |
pH observed |
Test Item added (mg/L) |
Time of shaking (h) |
Remarks |
Niobium concentration (µg/L) |
5.5 |
5.6 |
101 |
24 |
no solution observed |
0.022 |
6 |
6.0 |
100 |
24 |
no solution observed |
0.022 |
7 |
6.9 |
101 |
24 |
no solution observed |
0.030 |
8 |
7.9 |
101 |
24 |
no solution observed |
0.050 |
Within the tested range from pH 5.5 to 8, the vessel at pH=8 showed a higher concentration than the others. Therefore the main test was performed at pH=8.
Results preliminary test - concentration trend within 24h
Time |
"pH5.5" |
pH6 |
pH7 |
pH8 |
|
(µg/L) |
(µg/L) |
(µg/L) |
(µg/L) |
0 |
n.d. |
n.d. |
n.d. |
n.d. |
2 |
0.035 |
0.040 |
0.034 |
0.029 |
6 |
0.025 |
0.027 |
0.037 |
0.036 |
24 |
0.022 |
0.022 |
0.028 |
0.047 |
The solution buffered at pH 8 was found to be the media that maximized the solubility.
According to the preliminary test, the short and long term test was performed at pH 8.
Test results of the short term test period of one week (pH=8)
Sample |
Sampling |
Mean Conc. |
Mean Conc. |
|
time |
Nb (µg/L) |
Nb (µg/L) |
Control 1 |
0a |
n.d. |
n.d. |
Control 2 |
n.d. |
||
Vessel 1 mg-1 |
n.d. |
||
Vessel 1 mg-2 |
n.d. |
||
Vessel 1 mg-3 |
n.d. |
||
Vessel 10 mg-1 |
n.d. |
||
Vessel 10 mg-2 |
n.d. |
||
Vessel 10 mg-3 |
n.d. |
||
Vessel 100 mg-1 |
n.d. |
||
Vessel 100 mg-2 |
n.d. |
||
Vessel 100 mg-3 |
n.d. |
||
Control 1 |
2 hours |
n.d. |
n.d. |
Control 2 |
n.d. |
||
Vessel 1 mg-1 |
n.d. |
n.d. |
|
Vessel 1 mg-2 |
n.d. |
||
Vessel 1 mg-3 |
n.d. |
||
Vessel 10 mg-1 |
<0.01 |
<0.01 |
|
Vessel 10 mg-2 |
n.d. |
||
Vessel 10 mg-3 |
<0.01 |
||
Vessel 100 mg-1 |
0.039 |
0.041 |
|
Vessel 100 mg-2 |
0.043 |
||
Vessel 100 mg-3 |
0.040 |
||
Control 1 |
6 hours |
n.d. |
n.d. |
Control 2 |
n.d. |
||
Vessel 1 mg-1 |
n.d. |
n.d. |
|
Vessel 1 mg-2 |
n.d. |
||
Vessel 1mg-3 |
n.d. |
||
Vessel 10 mg-1 |
<0.01 |
<0.01 |
|
Vessel 10 mg-2 |
n.d. |
||
Vessel 10 mg-3 |
<0.01 |
||
Vessel 100 mg-1 |
0.044 |
0.046 |
|
Vessel 100 mg-2 |
0.051 |
||
Vessel 100 mg-3 |
0.043 |
||
Control 1 |
1 day |
n.d. |
|
Control 2 |
n.d. |
||
Vessel 1 mg-1 |
n.d. |
n.d. |
|
Vessel 1 mg-2 |
n.d. |
||
Vessel 1 mg-3 |
n.d. |
||
Vessel 10 mg-1 |
<0.01 |
<0.01 |
|
Vessel 10 mg-2 |
<0.01 |
||
Vessel 10 mg-3 |
0.011 |
||
Vessel100 mg-1 |
0.060 |
0.059 |
|
Vessel 100 mg-2 |
0.063 |
||
Vessel 100 mg-3 |
0.054 |
||
Control 1
|
2 day |
n.d. |
|
Control 2 |
n.d. |
||
Vessel 1 mg-1 |
<0.01 |
<0.01 |
|
Vessel 1 mg-2 |
n.d. |
||
Vessel 1 mg-3 |
<0.01 |
||
Vessel 10 mg-1 |
<0.01 |
<0.01 |
|
Vessel 10 mg-2 |
<0.01 |
||
Vessel 10 mg-3 |
0.012 |
||
Vessel 100 mg-1 |
0.072 |
0.071 |
|
Vessel 100 mg-2 |
0.076 |
||
Vessel 100 mg-3 |
0.065 |
||
Control 1 |
7 days |
n.d. |
|
Control 2 |
n.d. |
||
Vessel 1 mg-1 |
n.d. |
n.d. |
|
Vessel 1 mg-2 |
<0.01 |
||
Vessel 1 mg-3 |
<0.01 |
||
Vessel 10 mg-1 |
<0.01 |
<0.01 |
|
Vessel 10 mg-2 |
<0.01 |
||
Vessel 10 mg-3 |
0.018 |
||
Vessel 100 mg-1 |
0.104 |
0.104 |
|
Vessel 100 mg-2 |
0.111 |
||
Vessel 100 mg-3 |
0.098 |
Test results of the long term test period of four weeks:
Sample |
Sampling time |
Mean Conc. Nb (µg/L) |
Mean Conc.Nb (µg/L) |
Control 1 |
t = 0 |
n.d. |
n.d. |
Control 2 |
n.d. |
||
Vessel 1 |
n.d. |
||
Vessel 2 |
n.d. |
||
Vessel 3 |
n.d. |
||
Control 1 |
2 hours |
n.d. |
n.d. |
Control 2 |
n.d. |
||
Vessel 1 |
n.d. |
n.d. |
|
Vessel 2 |
n.d. |
||
Vessel 3 |
n.d. |
||
Control 1 |
6 hours |
n.d. |
n.d. |
Control 2 |
n.d. |
||
Vessel 1 |
n.d. |
n.d. |
|
Vessel 2 |
n.d. |
||
Vessel 3 |
n.d. |
||
Control 1 |
1 day |
n.d. |
n.d. |
Control 2 |
n.d. |
||
Vessel 1 |
n.d. |
n.d. |
|
Vessel 2 |
n.d. |
||
Vessel 3 |
n.d. |
||
Control 1 |
2 days |
n.d. |
n.d. |
Control 2 |
n.d. |
||
Vessel 1 |
n.d. |
n.d. |
|
Vessel 2 |
n.d. |
||
Vessel 3 |
n.d. |
||
Control 1 |
7 days |
n.d. |
n.d. |
Control 2 |
n.d. |
||
Vessel 1 |
n.d. |
n.d. |
|
Vessel 2 |
n.d. |
||
Vessel 3 |
n.d. |
||
Control 1 |
14 days |
n.d. |
n.d. |
Control 2 |
n.d. |
||
Vessel 1 |
n.d. |
<0.01 |
|
Vessel 2 |
n.d. |
||
Vessel 3 |
<0.01 |
||
Control 1 |
21 days |
n.d. |
n.d. |
Control 2 |
n.d. |
||
Vessel 1 |
n.d. |
n.d. |
|
Vessel 2 |
n.d. |
||
Vessel 3 |
n.d. |
||
Control 1 |
28 days |
n.d. |
n.d. |
Control 2 |
n.d. |
||
Vessel 1 |
n.d. |
n.d. |
|
Vessel 2 |
n.d. |
||
Vessel 3 |
n.d. |
t=0 samples were taken before the test item was added, to proof the purity of the test medium n.d.= not detectable (< 0.003 µg/L)
The specific area nor the particle size was not available and was not determined.
Preliminary test
pH that maximizes the concentration:
Temperature: 21.0 - 21.5 °C
pH planned |
pH observed |
Test item added (mg/L) |
Time of shaking (h) |
remarks |
Iron concentration (µg/L) |
5.5 |
5.7 |
100 |
24 |
No solution observed |
< LOQ (7.34) |
6. |
5.9 |
100 |
24 |
No solution observed |
< LOQ (4.81) |
7 |
6.8 |
100 |
24 |
No solution observed |
n.d. |
8 |
7.8 |
100 |
24 |
No solution observed |
n.d. |
Within the tested range from pH 5.5 to 8, the vessel at pH 5.5 showed a higher concentration than the others. Therefore the main test (long term test) was performed at pH=5.5, while the short term test was performed at pH=6.
Concentration Fe trend with 24h:
Temperature: 21.0 - 21.5 °C
Time |
pH=5.5 (µg/L) |
pH=6 (µg/L) |
pH=7 (µg/L) |
pH=8 (µg/L) |
0 |
n.d. |
n.d. |
n.d. |
n.d. |
2. |
n.d. |
n.d. |
n.d. |
n.d. |
6 |
n.d. |
n.d. |
n.d. |
n.d. |
24 |
LOQ (7.34) |
< LOQ (4.81) |
n.d. |
n.d. |
n.d. = not detectable (< 4.5 µg/L Fe)
LOQ = limit of quantification (15 µg/L Fe)
Short term test:
Temperature: 21.1 - 21.4 °C, pH=6
Content |
Conc. after 0 h (µg/L) |
Conc. after 2 h (µg/L) |
Conc. after 6 h (µg/L) |
Conc. on day 1 (µg/L) |
Conc. on day 2 (µg/L) |
Conc. on day 7 (µg/L) |
Conc. on day 14 (µg/L) |
Conc. on day 21 (µg/L) |
Conc. on day 28 (µg/L) |
|||||||||
|
Fe |
Nb |
Fe |
Nb |
Fe |
Nb |
Fe |
Nb |
Fe |
Nb |
Fe |
Nb |
Fe |
Nb |
Fe |
Nb |
Fe |
Nb |
Control 1 |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
Control 2 |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
1 mg/L – 1 |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
1 mg/L - 2 |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
1 mg/L – 3 |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
10 mg/L - 1 |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
- |
- |
- |
- |
- |
- |
10 mg/L – 2 |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
- |
- |
- |
- |
- |
- |
10 mg/L - 3 |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
- |
- |
- |
- |
- |
- |
100 mg/L - 1 |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
< LOQ |
n.d. |
< LOQ |
n.d. |
< LOQ |
n.d. |
- |
- |
- |
- |
- |
- |
100 mg/L – 2 |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
< LOQ |
n.d. |
< LOQ |
n.d. |
< LOQ |
n.d. |
- |
- |
- |
- |
- |
- |
100 mg/L - 3 |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
< LOQ |
n.d. |
< LOQ |
n.d. |
< LOQ |
n.d. |
- |
- |
- |
- |
- |
- |
n.d. = not detectable (< 4.5 µg/L Fe and < 0.045 µg/L Nb)
LOQ = limit of quantification (15 µg/L Fe and < 0.15 µg/L Nb)
During the 7 days solubility with test item, the determined concentration did not exceed 15 µg/L Fe and respectively 0.15 µg/L Nb (limit of quantification) for all taken samples. The concentration in the separate 28-day test of the 1 mg/L loading was not detectable for iron (< 4.5 µg/L Fe) and Nb (< 0.045 µg/L Nb) for all taken samples.
Long term test
Temperature: 21.1 - 21.5 °C, pH=5.5
Content |
Conc. after 0 h (µg/L) |
Conc. after 2 h (µg/L) |
Conc. after 6 h (µg/L) |
Conc. on day 1 (µg/L) |
Conc. on day 2 (µg/L) |
Conc. on day 7 (µg/L) |
Conc. on day 14 (µg/L) |
Conc. on day 21 (µg/L) |
Conc. on day 28 (µg/L) |
|||||||||
|
Fe |
Nb |
Fe |
Nb |
Fe |
Nb |
Fe |
Nb |
Fe |
Nb |
Fe |
Nb |
Fe |
Nb |
Fe |
Nb |
Fe |
Nb |
Control 1 |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
Control 2 |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
1 mg/L – 1 |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
1 mg/L - 2 |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
1 mg/L – 3 |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. |
n.d. = not detectable (< 4.5 µg/L Fe and < 0.045 µg/L Nb)
LOQ = limit of quantification (15 µg/L Fe and < 0.15 µg/L Nb)
During the 28 days solubility test with test item, the determined concentrations was not detectable for Fe (< 4.5 µg/L Fe) and Nb < 0.045 µg/L Nb) for all taken samples.
The very small parts of the very finely grounded material seem to build a suspension which is stable over a few days and very difficult to separate from the solution. Therefore the separation step is of high importance and done twice. Although the solution was visibly clear after the second separation, it cannot be excluded that a small amount of distributed test item is still present in the solution.
After filtration and centrifugation the following results were obtained:
Blank values |
Determination 1 |
Determination 2 |
Mean value |
Niobium content |
< 0.5 μg/l |
< 0.5 μg/l |
< 0.5 μg/l |
Iron content |
Not determined* |
< 10 μg/l |
< 10 μg/l |
Water solubility at 20 °C (after filtration and centrufigation) |
Flask 1 |
Flask 2 |
Flask 3 |
Mean value |
Niobium content Determination 1 |
< 0.5 µg/l |
< 0.5 µg/l |
0.85 μg/l |
|
Niobium content Determination 2 |
< 0.5 µg/l
|
< 0.5 µg/l
|
0.82 μg/ |
|
Niobium content (mean value) |
< 0.5 µg/l |
< 0.5 µg/l |
0.84 µg/l |
0.8 µg/l (1 µg/l Alloy) |
Iron content Determination 2 |
Not determined*
|
Not determined*
|
Not determined*
|
|
Iron content Determination 1 |
<10 μg/l |
<10 μg/l |
<10 μg/l |
|
Iron content (mean value) |
<10 μg/l
|
<10 μg/l
|
<10 μg/l
|
<10 μg/l
|
*Determination invalidated due to a carry-over.
Results
Preliminary Test
The test was performed according the description above obtaining the following results:
pH |
Test Item added (g/L) |
Time of shaking (h) |
Remarks |
Test Item conc. (µg/L) |
6 |
1 |
24 |
No solution observed |
0.05 |
7 |
1 |
24 |
No solution observed |
0.07 |
8 |
1 |
24 |
No solution observed |
0.12 |
The vessel at pH = 8 showed a clearly higher concentration than the vessles at pH = 5 and 6. Therefore the main test was performed at pH = 8.
The stability test of the buffer system over a period of one week showed, that the replacement of the gas phase is necessary with every sampling time. Results are shown in the table below:
Time |
pH 6 |
pH 7 |
pH 8 |
2 h |
6.2 |
5.8 |
7.8 |
6 h |
6.8 |
6.7 |
7.9 |
24 h |
6.2 |
6.8 |
7.9 |
48 h |
6.2 |
6.8 |
7.8 |
168 h |
6.1 |
6.7 |
7.8 |
Short Term Test
The short term test was performed as described above, obtaining the following results:
Test conditions during short term test period of one week
Sample |
Sampling time (h) |
Temperature (°C) |
pH |
Oxygen (%) |
Mean Conc. (µg/L) |
Mean ± RSD (µg/L ± %) |
Control 1 |
0 |
21.3 |
8.04 |
99 |
< 0.01 |
|
Control 2 |
21.3 |
8.04 |
99 |
< 0.01 |
|
|
Vessel 1 |
21.3 |
8.06 |
98 |
< 0.01 |
|
|
Vessel 2 |
21.3 |
8.08 |
98 |
< 0.01 |
|
|
Vessel 3 |
21.3 |
8.08 |
99 |
< 0.01 |
|
|
Vessel 4 |
21.3 |
8.08 |
99 |
< 0.01 |
|
|
Vessel 5 |
21.3 |
8.08 |
99 |
0.04 |
|
|
Control 1 |
2 |
21.1 |
7.94 |
100 |
< 0.01 |
|
Control 2 |
21.1 |
7.98 |
100 |
< 0.01 |
|
|
Vessel 1 |
21.1 |
7.96 |
99 |
0.20 |
0.21 +/- 12 |
|
Vessel 2 |
21.1 |
7.96 |
99 |
0.18 |
||
Vessel 3 |
21.1 |
7.94 |
100 |
0.23 |
||
Vessel 4 |
21.1 |
7.96 |
100 |
0.20 |
||
Vessel 5 |
21.1 |
7.95 |
100 |
0.24 |
||
Control 1 |
6 |
20.5 |
7.99 |
99 |
< 0.01 |
|
Control 2 |
20.5 |
8.01 |
99 |
< 0.01 |
|
|
Vessel 1 |
20.5 |
7.98 |
99 |
0.22 |
0.22 +/- 17 |
|
Vessel 2 |
20.5 |
7.98 |
99 |
0.22 |
||
Vessel 3 |
20.5 |
7.97 |
99 |
0.26 |
||
Vessel 4 |
20.5 |
7.97 |
99 |
0.16 |
||
Vessel 5 |
20.5 |
7.97 |
100 |
0.25 |
||
Control 1 |
24 |
20.5 |
8.01 |
99 |
< 0.01 |
|
Control 2 |
20.5 |
8.04 |
99 |
< 0.01 |
|
|
Vessel 1 |
20.5 |
8.02 |
98 |
0.33 |
0.33 +/- 7 |
|
Vessel 2 |
20.5 |
8.02 |
98 |
0.35 |
||
Vessel 3 |
20.5 |
8.00 |
98 |
0.33 |
||
Vessel 4 |
20.5 |
8.01 |
98 |
0.30 |
||
Vessel 5 |
20.5 |
8.01 |
99 |
0.35 |
||
Control 1 |
48 |
20.7 |
7.91 |
100 |
< 0.01 |
|
Control 2 |
20.7 |
7.97 |
100 |
< 0.01 |
|
|
Vessel 1 |
20.7 |
7.95 |
100 |
0.37 |
0.36 +/- 6 |
|
Vessel 2 |
20.7 |
7.95 |
100 |
0.39 |
||
Vessel 3 |
20.7 |
7.95 |
99 |
0.36 |
||
Vessel 4 |
20.7 |
7.96 |
100 |
0.33 |
||
Vessel 5 |
20.7 |
7.95 |
100 |
0.38 |
||
Control 1 |
168 |
20.5 |
7.78 |
99 |
< 0.01 |
|
Control 2 |
20.5 |
7.84 |
99 |
< 0.01 |
|
|
Vessel 1 |
20.5 |
7.81 |
99 |
0.44 |
0.43 +/- 8 |
|
Vessel 2 |
20.5 |
7.80 |
99 |
0.47 |
||
Vessel 3 |
20.5 |
7.79 |
100 |
0.41 |
||
Vessel 4 |
20.5 |
7.79 |
99 |
0.40 |
||
Vessel 5 |
20.5 |
7.80 |
99 |
0.43 |
A plot created from these data indicates an increasing saturation of niobium over the test period. After seven days the niobium concentration was still below 0.5 µg/L, although the final saturation couldn't be reached. Even an extrapolation of the curve up to a test duration of 28 days would lead to a theoretical concentration of merely 0.5 µg/L. Thus, it is considered to be justified that the solubility of Niobium metal in water is < 0.5 µg/L.
The water solubility of Niobium (powder form) was determined following OECD guideline 29. A 24 hour pre-test was performed in aqueous solution at pH 5.5, 6, 7 and 8.
The solution buffered at pH 8 was found to be the media that maximised the solubility. With this buffer a screening transformation/dissolution test was performed. The determined dissolved niobium concentrations in five test vessels with three samples each did not exceed 1.09 µg/L niobium for all taken samples, which is below LOQ.
The seven day short term test was performed with loadings of 10, 100 and 1000 mg test item per litre at pH 8. The concentrations after 7 days did not exceed 3.97 µg/L niobium for all taken samples. The concentrations in the separate 28 day test of the 10 mg/L loading at pH 8 did not exceed 0.587 µg/L niobium for all taken samples, which is below LOQ.
Description of key information
Water solubility tests according to OECD 105
< 0.5 µg/L at 20 °C, pH 6, Nb, massive form (Königer 2009)
< 0.8 µg/L at 20 °C, pH 6.2, FeNb granular form, particle size <0.4 mm
(Königer 2009)
Transformation/dissolution test OECD 29, Nb particle size 1 mm (Burkhard
2011):
< 0.01 µg/L at 21°C, pH 8, after 7 days, 1 mg/L loading rate, particle
size about 1 mm
< 0.01 µg/L at 21°C, pH 8, after 7 days, 10 mg/L loading rate, particle
size about 1 mm
0.104 µg/L at 21°C, pH 8, after 7 days, 100 mg/L loading rate, particle
size about 1 mm
< 0.01 µg/L at 21°C, pH 8, after 28 days, 1 mg/L loading rate, particle
size about 1 mm
Transformation/dissolution test OECD 29, granular form, FeNb < 0.4 mm
(Burkhard 2012):
<15 µg/L Fe and <0.15 µg/L Nb at 21.4 °C, pH=6, after 7 days, 100 mg/L
loading rate, granular form
<4.5 µg/L Fe and <0.045 µg/L Nb at 21.5 , pH=5.5, after 28 days, 1 mg/L
loading rate, granular form
Transformation/dissolution test OECD 29, Nb, powder form, D50 25.4 µm (Wild 2015):
<0.4 µg/L Nb at 20 °C, pH=8, after 7 days, 10 mg/L loading rate
2.77 µg/L Nb at 20 °C, pH=8, after 7 days, 100 mg/L loading rate
3.50 µg/L Nb at 20 °C, pH=8, after 7 days, 1000 mg/L loading rate
<0.4 µg/L Nb at 20 °C, pH=8, after 28 days, 10 mg/L loading rate
Transformation/dissolution test OECD 29, FeNb, Fines M45 (40 -250 µm), Koch 2021
23.8 µg/L Fe at 20 °C, pH 5.5, after 7 days, 100 mg/L loading rate
< 4.04 µg/L Fe at 20 °C, pH 5.5, after 7 days, 10 mg/L loading rate
< 4.04 µg/L Fe at 20 °C, pH 5.5, after 7 days, 1 mg/L loading rate
< 4.04 µg/L Fe at 20 °C, pH 5.5, after 28 days, 1 mg/L loading rate
2.97 µg/L Nb at 20 °C, pH 8.5, after 7 days, 100 mg/L loading rate
1.47 µg/L Nb at 20 °C, pH 8.5, after 7 days, 10 mg/L loading rate
< 0.15 µg/L Nb at 20 °C, pH 8.5, after 7 days, 1 mg/L loading rate
0.302 µg/L Nb at 20 °C, pH 8.5, after 28 days, 1 mg/L loading rate
Key value for chemical safety assessment
Additional information
The water solubility of the test substance was determined under flask conditions according to OECD guideline 105 and is stated to be < 0.5 µg/L (massive form) and 0.8 µg/L and (granular form). The value 0.8 µg/L is the maximum measured value. The two other values were below the detection limit (< 0.5 µg/L). The water solubility (solubility in aqueous media) was also performed according to OECD series on Testing and Assessment Number 29.
The Guidance on information requirements and Chemical Safety Assessment, Chapter R.7a: Endpoint specific guidance, Version 2.3, December 2013 recommend for metals to perform the test relating to OECD series on Testing and Assessment Number 29 - Guidance Document on Transformation/Dissolution of Metals and Metal Compounds in Aqueous media. This method can be used to determine the rate and extent to which metals and sparingly soluble metal compounds can produce soluble bioavailable ionic and other metal-bearing species in aqueous media.
Several tests according OECD series on Testing and Assessment Number 29 were performed.
The first test (Kirchmaier, R., 2010) a short term test (7 days) was performed with a loading of 3 g/L instead of the 1, 10 or 100 mg/L mentioned in the guideline due to particle size and physical properties of the massive niobium. After seven days the niobium concentration was still below 0.5 μg/L, although the final saturation couldn’t be reached. Even an extrapolation of the curve (concentration versus time) up to a test duration of 28 days would lead to a theoretical concentration of merely 0.5 μg/L. Thus, it is considered to be justified that the solubility of niobium metal in water is < 0.5 μg/L.
The second test (Burkhard, A. 2011) was performed as a 7 day short term test with loadings of 1, 10 and 100 mg/L at pH 8 and a long term test 28 days with loading of 1 mg/L. For the loading of 1 and 10 mg/L the solubility of niobium metal was below 0.01 µg/L at pH 8. The loading of 100 mg/L indicated a solubility of 0.104 µg/L niobium at pH 8 after the 7 days. The solubility of niobium was found to be below 0.01 µg/L for the 28 day long term test at pH 8.
The third test (Burkhard, A. 2012) was performed with ferro niobium in granular form (MMAD: 991 µm) as a 7 day short term test with loadings of 1, 10 and 100 mg/L at pH 6 and a long term test 28 days with loading of 1 mg/L at pH=5.5. The loading of 100 mg/L indicated a solubility of 0.15 µg/L niobium (Fe below 15 µg/L) at pH 6 after the 7 days.
For the loading of 1 mg/L the solubility of niobium in granular form (MMAD: 991 µM) was below 0.045 µg/L (Fe below 4.5 µg/L) at pH 5.5 after 28 d. The solubility of ferro niobium in granular form was found to be below 39.96 µg/L (quantification limit) for the 28 day long term test at pH 5.5.
A further test (Wild, C. 2015) according to OECD series 29 was performed with niobium in powder form (D50 25.4 µm).
The solubility of Nb was determinded to be <0.4 µg/L at pH 8 at 10 mg/L loanding rate and 2.77 µg/L at loading rate 100 mg/L and 3.0 µg/L at loading rate 1000 mg/L in the short term test and < 0.4 µg/L in the long term test (28 days) at 10 mg/L loading rate.
A further test (Koch, D. 2021) according to OECD series 29 was performed with ferro niobium in granular/powder form (Fines M45 ;40 -250 µm; MMAD 485 µm).
The solubility of Fe was investigated in a short term test (7 days) with loadings of 1, 10 und 100 mg/L at pH 5.5 at room temperature and in a long term test (28 days), loading rate 1 mg/L at pH 5.5. at room temperature. The solubility of Fe was determinded to be 23.8 µg/L at pH 5.5 at 100 mg/L loanding rate and < 4.04 µg/L at loading rates 1 and 10 mg/L in the short term test and < 4.04 µg/L in the long term test (28 days).
The solubility of Nb was determined to be 2.97 µg/L at pH 8.5 at 100 mg/L loading rate and 1.47 µg/L at loading rate 10 mg/L and < 0.15 µg/L at loading rate 1 mg/L in the short term test and 0.302 µg/L in the long term test (28 days).
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