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EC number: 215-214-1 | CAS number: 1313-97-9
- Life Cycle description
- Uses advised against
- Endpoint summary
- Appearance / physical state / colour
- Melting point / freezing point
- Boiling point
- Density
- Particle size distribution (Granulometry)
- Vapour pressure
- Partition coefficient
- Water solubility
- Solubility in organic solvents / fat solubility
- Surface tension
- Flash point
- Auto flammability
- Flammability
- Explosiveness
- Oxidising properties
- Oxidation reduction potential
- Stability in organic solvents and identity of relevant degradation products
- Storage stability and reactivity towards container material
- Stability: thermal, sunlight, metals
- pH
- Dissociation constant
- Viscosity
- Additional physico-chemical information
- Additional physico-chemical properties of nanomaterials
- Nanomaterial agglomeration / aggregation
- Nanomaterial crystalline phase
- Nanomaterial crystallite and grain size
- Nanomaterial aspect ratio / shape
- Nanomaterial specific surface area
- Nanomaterial Zeta potential
- Nanomaterial surface chemistry
- Nanomaterial dustiness
- Nanomaterial porosity
- Nanomaterial pour density
- Nanomaterial photocatalytic activity
- Nanomaterial radical formation potential
- Nanomaterial catalytic activity
- Endpoint summary
- Stability
- Biodegradation
- Bioaccumulation
- Transport and distribution
- Environmental data
- Additional information on environmental fate and behaviour
- Ecotoxicological Summary
- Aquatic toxicity
- Endpoint summary
- Short-term toxicity to fish
- Long-term toxicity to fish
- Short-term toxicity to aquatic invertebrates
- Long-term toxicity to aquatic invertebrates
- Toxicity to aquatic algae and cyanobacteria
- Toxicity to aquatic plants other than algae
- Toxicity to microorganisms
- Endocrine disrupter testing in aquatic vertebrates – in vivo
- Toxicity to other aquatic organisms
- Sediment toxicity
- Terrestrial toxicity
- Biological effects monitoring
- Biotransformation and kinetics
- Additional ecotoxological information
- Toxicological Summary
- Toxicokinetics, metabolism and distribution
- Acute Toxicity
- Irritation / corrosion
- Sensitisation
- Repeated dose toxicity
- Genetic toxicity
- Carcinogenicity
- Toxicity to reproduction
- Specific investigations
- Exposure related observations in humans
- Toxic effects on livestock and pets
- Additional toxicological data
Water solubility
Administrative data
Link to relevant study record(s)
- Endpoint:
- water solubility
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 22 October 2007 - 5 December 2007
- 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 (incl. QA statement)
- Type of method:
- column elution method
- Water solubility:
- 7.8 µg/L
- Temp.:
- 20 °C
- pH:
- 6.64 - 6.87
- Details on results:
- The measured results differ by less than 30 %. Therefore, the study is considered to be valid.
- Conclusions:
- Interpretation of results: insoluble (< 0.1 mg/L)
The water solubility at 20 °C was determined to be 7.8 µg/L (standard deviation ± 0.41 µg/L) using the column elution method. - Executive summary:
The determination of the water solubility of the test material was performed using the column elution method in accordance with the standardised guidelines OECD 105 and EU Method A.6.
During pre-tests the water solubility of the test material at room temperature was estimated to be < 9.45 mg/L by visual judgment. Therefore, the column elution method was used for the performance of the main test.
During the main test six samples were analysed in the first run (0.52 mL/min) and six samples during the second run (0.26 mL/min), each with a sampling interval of one hour. Total elution time was 165 hours.
The water solubility was calculated in accordance with the content of the test material given in the certificate of analysis.
The water solubility at 20 °C was determined to be 7.8 µg/L (standard deviation ± 0.41 µg/L) using the column elution method.
- Endpoint:
- water solubility
- Type of information:
- experimental study
- Adequacy of study:
- supporting study
- Study period:
- not reported
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- other: see 'Remark'
- Remarks:
- Valid with restrictions. This is peer reviewed data where the test methodology and identity of the substance have been evaluated, and a reliable and representative value for the endpoint has been selected. No information on GLP status or test guideline followed is available.
- Qualifier:
- no guideline available
- Principles of method if other than guideline:
- Handbook data does not specify the method. Data from peer reviewed source.
- GLP compliance:
- not specified
- Water solubility:
- 0 other: g-mol/L
- Temp.:
- 29 °C
- Remarks on result:
- other: No pH reported.
- Water solubility:
- 1.9 mg/L
- Temp.:
- 29 °C
- Remarks on result:
- other: No pH reported.
- Conclusions:
- Interpretation of results: slightly soluble (0.1-100 mg/L)
The test material has a water solubility of 0.0000057 g-mol/L (equivalent to 1.9 mg/L) at 29 °C and as such can be described as slightly soluble. - Executive summary:
The test material has a water solubility of 0.0000057 g-mol/L (equivalent to 1.9 mg/L) at 29 °C and as such can be described as slightly soluble.
- Endpoint:
- transformation / dissolution of metals and inorganic metal compounds
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 14 December 2019 to 20 December 2019
- 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
- Version / remarks:
- 2001
- Deviations:
- no
- GLP compliance:
- yes
- Other quality assurance:
- ISO/IEC 17025 (General requirements for the competence of testing and calibration laboratories)
- Type of method:
- other: Transformation/dissolution test
- Specific details on test material used for the study:
- TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: The test material as received fulfilled the <1 mm size condition. Therefore, no further preparation of the test material was needed. The Sponsor also provided the required document with the characteristics of the test material. - Type of test:
- screening transformation/dissolution test - sparingly soluble metal compounds
- Mean dissolved conc.:
- 3 166 µg/L
- Element analysed:
- Neodymium
- Loading of aqueous phase:
- 100 mg/L
- Incubation duration:
- 24 h
- Test conditions:
- pH 6, 21.5 °C - 21.7 °C.
- Type of test:
- screening transformation/dissolution test - sparingly soluble metal compounds
- Mean dissolved conc.:
- 142 µg/L
- Element analysed:
- Neodymium
- Loading of aqueous phase:
- 100 mg/L
- Incubation duration:
- 24 h
- Test conditions:
- pH 8, 21.5 °C - 21.7 °C.
- Details on results:
- The temperature of the test solutions fluctuated between 21.5 °C and 21.7 °C, which was in line with the test conditions of 20 °C – 23 °C.
The test material has no immediate influence on the pH of the test system. The pH measured in the medium at the start of the test, and in the blank and test material vessels during the test at pH 6 and pH 8 varied from 5.97 to 6.01 and from 7.97 to 8.02, respectively. The measured data at pH 6 and pH 8 were within the specifications of ± 0.2 units of pH.
The dissolved oxygen concentration measured in the blank and test material vessels at pH 6 and pH 8 varied from 8.39 to 8.53 mg/L O2 and from 8.40 to 8.51 mg/L O2, respectively. These values were higher than the required value of ± 6 mg/L O2 at 22 °C, corresponding to a minimal saturation level in the air of 70 %.
The measured TOC of the test media were <1.0 mg/L C, and below the required level of 2.0 mg/L C as laid down in the OECD Test Guidance no.29.
The test media at the start of the test and the blank control vessels during the test showed concentrations below or close to the limit of detection of 0.02 μg/L Nd. The limit of detection was determined as the rounded-up values of three times the standard deviation of the element of all blank (pH 6 and pH 8) measurements in this study (N = 12).
Note that throughout the report, the overall standard deviation and coefficient of variation of all 9 measured values were given as this is the most comprehensive representation. However, the between-vessel standard deviation and coefficient of variation are shown here as these are subject to the accepted quality criteria for dissolution testing.
The following observations could be made in the test vessels at the nominal pH 6 with a loading of 100 mg/L test material:
- A dissolved concentration of 3 166 ± 89 μg/L Nd was found at the 24 hours endpoint with a between-vessel coefficient of variation of 3 % (N = 3) which met the <20 % quality criterion at the 24 hours endpoint. The within-vessel coefficients of variation met the <10 % quality criterion for all test vessels.
Based on the specific surface area of the Test material powder (i.e. 4.7 m^2/g test material), a neodymium release per surface of 6.74 mg/m² was calculated at the 24 hours endpoint.
Based on the neodymium content of the test material (85.73 % Nd) and the average dissolved neodymium concentration, a neodymium release of approximately 3.69 % could be calculated at the 24 hours endpoint.
The following observations could be made in the test vessels at the nominal pH 8 with a loading of 100 mg/L test material:
- A dissolved concentration of 142 ± 1 μg/L Nd was found at the 24 hours endpoint with a between-vessel coefficient of variation of 1 % (N = 3) which met the <20 % quality criterion at the 24 hours endpoint. The within-vessel coefficients of variation met the <10 % quality criterion for all test vessels.
Based on the specific surface area of the test material powder (i.e. 4.7 m^2/g test material), a neodymium release per surface of 0.30 mg/m^2 was calculated at the 24 hours endpoint.
Based on the neodymium content of the test material (85.73 % Nd) and the average dissolved neodymium concentration, a neodymium release of approximately 0.17 % could be calculated at the 24 hours endpoint. - Conclusions:
- Under the conditions of the study with the test material at a loading of 100 mg/L, it was shown that for neodymium, an average concentration of 3 166 μg/L Nd (CVoverall = 3 %; N = 9) was measured at pH 6 (i.e. 3.69 % neodymium release) and 142 μg/L Nd (CVoverall = 1 %; N = 9) at pH 8 (i.e., 0.17 % neodymium release), after 24 hours of exposure to the test medium at pH 6 and pH 8, respectively.
Based on the rounded results, of the dissolved element concentrations, we may conclude that pH 6 is the pH where the highest concentrations of neodymium were measured.
The results can be assumed reliable since the test conditions stayed constant during the experiment. - Executive summary:
The dissolution characteristics of the test material were assessed according to OECD Test Guideline 29 and in compliance with GLP.
The pH-dependent extent of dissolution of the test material was tested in standard aqueous solutions at pH 6 (0.5 % CO2-buffering) and pH 8 (air-buffering) for 24 hours at an agitation speed of 100 revolutions per minute (rpm). The extent of the transformation/dissolution was measured as the dissolved neodymium concentrations obtained after 24 hours.
All test parameter conditions were fully following the OECD Test Guideline 29 requirements:
• The measured TOC of the media were <1.0 mg/L C and below the required level of 2.0 mg/L C.
• The temperature of the test solutions fluctuated between 21.5 °C and 21.7 °C and corresponded to the required test conditions of 20 °C – 23 °C.
• The pH measured in the medium at the start of the test, and in the blank and test material vessels during the test at pH 6 and pH 8 varied from 5.97 to 6.01 and from 7.97 to 8.02, respectively. The measured data at pH 6 and pH 8 were within the specifications of ± 0.2 units of pH.
• The dissolved oxygen concentration measured in the blank and test material vessels at pH 6 and pH 8 varied from 8.39 to 8.53 mg/L O2 and from 8.40 to 8.51 mg/L O2, respectively. These values were higher than the required value of ± 6 mg/L O2 at 22 °C, corresponding to a minimal saturation level in the air of 70 %.
The test media at the start of the test and the blank control vessels during the test showed concentrations below or close to the limit of detection of 0.02 μg/L Nd. The limit of detection was determined as the rounded-up values of three times the standard deviation of the element of all blank (pH 6 and pH 8) measurements in this study (N = 12).
For the test at nominal pH 6 at a loading of 100 mg/L test material, an average dissolved concentration of:
• 3 166 ± 80 μg/L neodymium (CVoverall = 3 %; N = 9) was found at the 24 hours endpoint.
Based on the specific surface area of the test material (i.e. 4.7 m^2 /g test material), this corresponds to an element release per surface of:
• 6.74 mg/m^2 neodymium.
Based on the element content in the test material and the average dissolved element concentration in the test solution:
• A release of neodymium of 3.69 % of the content, could be calculated at the 24 hours endpoint in test medium at pH 6.
For the test at nominal pH 8 at a loading of 100 mg/L test material, an average dissolved concentration of:
• 142 ± 1 μg/L neodymium (CVoverall = 1 %; N = 9), were found at the 24 hours endpoint.
Based on the specific surface area of the test material (i.e. 4.7 m^2 /g test material), this corresponds to an element release per surface of:
• 0.30 mg/^2 neodymium.
Based on the element content in the test material and the average dissolved element concentration in the test solution:
• A release of neodymium of 0.17 % of the content, could be calculated at the 24 hours endpoint in test medium at pH 8.
Based on the results of the experiments, we may conclude that nominal “pH 6” is the pH where the highest dissolved neodymium concentrations were measured. This dissolution result may be important in the design of the standard 7 days and 28 days transformation/dissolution test to enable appropriate hazard classification categories under EU-CLP and UN-Globally Harmonized System.
Referenceopen allclose all
Table 1: Water solubility (Column-Elution-Method)
Experiment No. |
Flow rate (mL/h) |
Sample No. |
Concentration analysed* (µg Nd/L) |
Water solubility calculated (µg test material/L) |
Water solubility calculated (µg test material/L) |
Water solubility calculated (µg test material/L) |
pH |
1 |
31 |
1 2 3 4 5 6 |
5.8 6.2 5.9 5.7 5.9 5.9 |
7.43 7.94 7.56 7.30 7.56 7.56 |
7.559 SD = ± 0.241 Srel = ± 2.84 % |
7.80 SD = ± 0.41 Srel = ± 5.26 % |
6.87 6.80 6.79 6.75 6.64 6.83 |
2 |
16 |
7 8 9 10 11 12 |
6.3 5.9 6.0 6.5 6.8 6.2 |
8.07 7.56 7.69 8.33 8.71 7.94 |
8.050 SD = ± 0.424 Srel = ± 5.27 % |
6.77 6.67 6.83 6.76 6.85 6.86 |
SD = Standard deviation
*Values measured by ICP / MS
24-hours Screening test at 100 rpm on the test material. Data of measured dissolved element concentrations, temperature, pH, and dissolved oxygen concentration of blank control vessel at pH 6.
Blank |
μg/L Nd |
T (°C) |
pH |
DO (mg/L O2) |
pH 6 at 100 rpm |
24 h |
|||
Detection limit |
0.02 |
|||
Validated report limit |
0.5 |
|||
Replica 1 spl1 |
<0.02 |
21.6 |
5.99 |
8.50 |
Replica 1 spl2 |
<0.02 |
|||
Replica 1 spl3 |
<0.02 |
|||
Xavg,1 |
<0.02 |
|||
Swithin,1 |
- |
|||
CVwithin,1 (%) |
- |
Xavg,v: Within vessel average of 3 samples where v is the blank control vessel replica number (N = 3).
Swithin,v: Within vessel standard deviation where v is the blank control vessel replica number (N = 3).
CVwithin, v: Within Vessel Coefficient of Variation where v is the blank control vessel replica number (N = 3).
24-hours Screening test at 100 rpm on the test material at a 100mg/L loading in a standard aqueous medium at pH 6. Data of measured dissolved element concentrations, temperature, pH and dissolved oxygen concentration in test vessels.
100 mg/L Test Material |
μg/L Nd |
T (°C) |
pH |
DO (mg/L O2) |
pH 6 at 100 rpm |
24 h |
|||
Detection limit |
0.02 |
|||
Validated report limit |
0.5 |
|||
Replica 1 spl1 |
3 094 |
21.6 |
3.01 |
8.39 |
Replica 1 spl2 |
3 060 |
|||
Replica 1 spl3 |
3 049 |
|||
Xavg,1 |
3 068 |
|||
Swithin,1 |
24 |
|||
CVwithin,1 (%) |
1 |
|||
Replica 2 spl1 |
3 275 |
21.6 |
6.00 |
8.47 |
Replica 2 spl2 |
3 233 |
|||
Replica 1 spl3 |
3 214 |
|||
Xavg,2 |
3 241 |
|||
Swithin,2 |
31 |
|||
CVwithin,2 (%) |
1 |
|||
Replica 3 spl1 |
3 190 |
21.7 |
6.01 |
8.46 |
Replica 3 spl2 |
3 173 |
|||
Replica 3 spl3 |
3 210 |
|||
Xavg,3 |
3 191 |
|||
Swithin,3 |
18 |
|||
CVwithin,3 (%) |
1 |
|||
Xavg |
3 166 |
|
||
Sbetween |
89 |
|||
CVbetween (%) |
3 |
|||
Soverall |
80 |
|||
CVoverall (%) |
3 |
Xavg,v: Within vessel average of 3 samples where v is the blank control vessel replica number (N = 3).
Swithin,v: Within vessel standard deviation where v is the blank control vessel replica number (N = 3).
CVwithin, v: Within Vessel Coefficient of Variation where v is the blank control vessel replica number (N = 3).
Xavg: Average of 3 vessels (3 samples per test vessel; blank corrected) (N = 3)
Sbetween: Between vessel standard deviation (N = 3)
CVbetween: Between vessel Coefficient of Variation (N = 3)
Soverall: Overall Standard Deviation (N = 9)
CVoverall: Overall Coefficient of Variation (N = 9)
24-hours Screening test at 100 rpm on the test material. Data of measured dissolved element concentrations, temperature, pH, and dissolved oxygen concentration of blank control vessel at pH 8.
Blank |
μg/L Nd |
T (°C) |
pH |
DO (mg/L O2) |
pH 8 at 100 rpm |
24 h |
|||
Detection limit |
0.02 |
|||
Validated report limit |
0.5 |
|||
Replica 1 spl1 |
<0.02 |
21.76 |
8.01 |
8.44 |
Replica 1 spl2 |
<0.02 |
|||
Replica 1 spl3 |
<0.02 |
|||
Xavg,1 |
<0.02 |
|||
Swithin,1 |
- |
|||
CVwithin,1 (%) |
- |
Xavg,v: Within vessel average of 3 samples where v is the blank control vessel replica number (N = 3).
Swithin,v: Within vessel standard deviation where v is the blank control vessel replica number (N = 3).
CVwithin, v: Within Vessel Coefficient of Variation where v is the blank control vessel replica number (N = 3).
24-hours Screening test at 100 rpm on the test material at a 100mg/L loading in a standard aqueous medium at pH 8. Data of measured dissolved element concentrations, temperature, pH and dissolved oxygen concentration in test vessels.
100 mg/L Test Material |
μg/L Nd |
T (°C) |
pH |
DO (mg/L O2) |
pH 8 at 100 rpm |
24 h |
|||
Detection limit |
0.02 |
|||
Validated report limit |
0.5 |
|||
Replica 1 spl1 |
140 |
21.6 |
8.02 |
8.46 |
Replica 1 spl2 |
144 |
|||
Replica 1 spl3 |
143 |
|||
Xavg,1 |
142 |
|||
Swithin,1 |
2 |
|||
CVwithin,1 (%) |
1 |
|||
Replica 2 spl1 |
141 |
21.7 |
8.01 |
8.42 |
Replica 2 spl2 |
140 |
|||
Replica 1 spl3 |
143 |
|||
Xavg,2 |
142 |
|||
Swithin,2 |
1 |
|||
CVwithin,2 (%) |
1 |
|||
Replica 3 spl1 |
140 |
21.6 |
8.01 |
8.40 |
Replica 3 spl2 |
142 |
|||
Replica 3 spl3 |
142 |
|||
Xavg,3 |
141 |
|||
Swithin,3 |
1 |
|||
CVwithin,3 (%) |
1 |
|||
Xavg |
142 |
|
||
Sbetween |
1 |
|||
CVbetween (%) |
1 |
|||
Soverall |
1 |
|||
CVoverall (%) |
1 |
Xavg,v: Within vessel average of 3 samples where v is the blank control vessel replica number (N = 3).
Swithin,v: Within vessel standard deviation where v is the blank control vessel replica number (N = 3).
CVwithin, v: Within Vessel Coefficient of Variation where v is the blank control vessel replica number (N = 3).
Xavg: Average of 3 vessels (3 samples per test vessel; blank corrected) (N = 3)
Sbetween: Between vessel standard deviation (N = 3)
CVbetween: Between vessel Coefficient of Variation (N = 3)
Soverall: Overall Standard Deviation (N = 9)
CVoverall: Overall Coefficient of Variation (N = 9)
Summarised results of the measured element concentrations after 24 hours of transformation/ dissolution of the test material at 100 rpm at pH 6:
Analyte |
Xavg ± Soverall |
CVoverall |
Element Assay Test Material |
Theoretical Maximum Expected |
Solubility Translation Factor (MeClas) |
Neodymium (Nd) |
3 166 ± 80 μg/L 6.74 mg/m^2 |
3 % |
85.73 % |
85.73 mg/L |
3.69 % |
Xavg: Average of 3 vessels (3 samples per test vessel) (N = 9)
Soverall: Overall Standard Deviation (N = 9)
CVoverall: Overall Coefficient of Variation (N = 9)
Summarised results of the measured element concentrations after 24 hours of transformation/ dissolution of the test material at 100 rpm at pH 8:
Analyte |
Xavg ± Soverall |
CVoverall |
Element Assay Test Material |
Theoretical Maximum Expected |
Solubility Translation Factor (MeClas) |
Neodymium (Nd) |
142 ± 1 μg/L 0.30 mg/m^2 |
1 % |
85.73 % |
85.73 mg/L |
0.17 % |
Xavg: Average of 3 vessels (3 samples per test vessel) (N = 9)
Soverall: Overall Standard Deviation (N = 9)
CVoverall: Overall Coefficient of Variation (N = 9)
Description of key information
Water Solubility: RCC (2008)
The water solubility at 20 °C was determined to be 7.8 µg/L (standard deviation ± 0.41 µg/L) using the column elution method.
Transformation/Dissolution Study: Brouwers (2019)
Under the conditions of the study with the test material at a loading of 100 mg/L, it was shown that for neodymium, an average concentration of 3 166 μg/L Nd (CVoverall = 3 %; N = 9) was measured at pH 6 (i.e. 3.69 % neodymium release) and 142 μg/L Nd (CVoverall = 1 %; N = 9) at pH 8 (i.e., 0.17 % neodymium release), after 24 hours of exposure to the test medium at pH 6 and pH 8, respectively.
Based on the rounded results, of the dissolved element concentrations, we may conclude that pH 6 is the pH where the highest concentrations of neodymium were measured.
The results can be assumed reliable since the test conditions stayed constant during the experiment.
Key value for chemical safety assessment
- Water solubility:
- 7.8 µg/L
- at the temperature of:
- 20 °C
Additional information
Water Solubility: RCC (2008)
The key study was conducted in line with GLP and the standardised guidelines OECD 105 and EU Method A.6. It was assigned a reliability score of 1 in accordance with the criteria detailed by Klimisch (1997).
The determination of the water solubility of the test material was performed using the column elution method. During pre-tests, the water solubility of the test material at room temperature was estimated to be < 9.45 mg/L by visual judgment. Therefore, the column elution method was used for the performance of the main test.
During the main test, six samples were analysed in the first run (0.52 mL/min) and six samples during the second run (0.26 mL/min), each with a sampling interval of one hour. Total elution time was 165 hours. The water solubility was calculated in accordance with the content of the test material given in the certificate of analysis.
The water solubility at 20 °C was determined to be 7.8 µg/L (standard deviation ± 0.41 µg/L) using the column elution method.
Supporting information is provided in the form of handbook data. As this is peer-reviewed information, it was awarded a reliability score of 2 in accordance with the criteria set forth by Klimisch (1997).
O'Neil, M.J., et al. (2006) reports that the test material has a water solubility of 0.0000057 g-mol/L (equivalent to 1.9 mg/L) at 29 °C.
Transformation/Dissolution Study: Brouwers (2019)
The dissolution characteristics of the test material were assessed according to OECD Test Guideline 29 and in compliance with GLP. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).
The pH-dependent extent of dissolution of the test material was tested in standard aqueous solutions at pH 6 (0.5 % CO2-buffering) and pH 8 (air-buffering) for 24 hours at an agitation speed of 100 revolutions per minute (rpm). The extent of the transformation/dissolution was measured as the dissolved neodymium concentrations obtained after 24 hours.
All test parameter conditions were fully following the OECD Test Guideline 29 requirements:
• The measured TOC of the media were <1.0 mg/L C and below the required level of 2.0 mg/L C.
• The temperature of the test solutions fluctuated between 21.5 °C and 21.7 °C and corresponded to the required test conditions of 20 °C – 23 °C.
• The pH measured in the medium at the start of the test, and in the blank and test material vessels during the test at pH 6 and pH 8 varied from 5.97 to 6.01 and from 7.97 to 8.02, respectively. The measured data at pH 6 and pH 8 were within the specifications of ± 0.2 units of pH.
• The dissolved oxygen concentration measured in the blank and test material vessels at pH 6 and pH 8 varied from 8.39 to 8.53 mg/L O2 and from 8.40 to 8.51 mg/L O2, respectively. These values were higher than the required value of ± 6 mg/L O2 at 22 °C, corresponding to a minimal saturation level in the air of 70 %.
The test media at the start of the test and the blank control vessels during the test showed concentrations below or close to the limit of detection of 0.02 μg/L Nd. The limit of detection was determined as the rounded-up values of three times the standard deviation of the element of all blank (pH 6 and pH 8) measurements in this study (N = 12).
For the test at nominal pH 6 at a loading of 100 mg/L test material, an average dissolved concentration of:
• 3 166 ± 80 μg/L neodymium (CVoverall = 3 %; N = 9) was found at the 24 hours endpoint.
Based on the specific surface area of the test material (i.e. 4.7 m^2 /g test material), this corresponds to an element release per surface of:
• 6.74 mg/m^2 neodymium.
Based on the element content in the test material and the average dissolved element concentration in the test solution:
• A release of neodymium of 3.69 % of the content, could be calculated at the 24 hours endpoint in test medium at pH 6.
For the test at nominal pH 8 at a loading of 100 mg/L test material, an average dissolved concentration of:
• 142 ± 1 μg/L neodymium (CVoverall = 1 %; N = 9), were found at the 24 hours endpoint.
Based on the specific surface area of the test material (i.e. 4.7 m^2 /g test material), this corresponds to an element release per surface of:
• 0.30 mg/^2 neodymium.
Based on the element content in the test material and the average dissolved element concentration in the test solution:
• A release of neodymium of 0.17 % of the content, could be calculated at the 24 hours endpoint in test medium at pH 8.
Based on the results of the experiments, we may conclude that nominal “pH 6” is the pH where the highest dissolved neodymium concentrations were measured. This dissolution result may be important in the design of the standard 7 days and 28 days transformation/dissolution test to enable appropriate hazard classification categories under EU-CLP and UN-Globally Harmonized System.
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