Neodymium oxide

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:

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.

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

 

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.

Reference 2

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.

Reference 3

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.

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)

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.

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.