Germanium

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

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Justification for type of information:

see section 13 in IUCLID for read-across justification

Qualifier:

no guideline available

Principles of method if other than guideline:

For the chronic aquatic effects classification of substances, it is needed to assess their "rapid degradability". This concept, which is characteristic for organic substances, is not applicable to metals. For this reason, the concept of removal from the water column has been developed. This measures the amount of metal that remains in the water column upon addition, and thus, the potential for exerting a chronic effect. in analogy with the degradability protocol for organic substances, the refernce point is 70% or more removal after 28 days. If this is observed the substance can be considered as "equivalent to rapidly degradable" in the sense of chronic aquatic toxicity. The approach is still under development and discussion. Rather than rely on modelling, it was decided to setup an experiment, according to the present state of the discussions, and in the medium used for transformation dissolution testing according to OECD 29.

GLP compliance:

not specified

Type of method:

flask method

Key result

Type of test:

other: removal from the water column test

Mean dissolved conc.:

ca. 20 other: %

Element analysed:

Ge

Loading of aqueous phase:

10 g/L

Incubation duration:

28 d

Test conditions:

test medium according to OECD 29

Remarks on result:

other: 80 % Ge-removal from the water column after 28 days

GeO2 was fully dissolved at the start of the experiment. Ge concentration in the water column rapidly decreased to reach a level of 20% after 28 days. after resuspension, the Ge concentration remained at the low level; so, Ge did not enter back into the water column in dissolved form.

time (hrs)	Ge concentration replica 1	Ge concentration replica 2	% removal from water column (mean)
0	974.9	974.9	2.5
6	812.9	795.0	17.5
24	761.9	750.6	22.4
96	517.8	505.7	47.5
168	432.4	409.7	56.8
672	228.5	173.3	79.4
after resuspension 673.5	223.6	170.9	79.8
675	220.0	168.0	80.1
679	218.6	171.7	80.0
697	212.5	166.3	80.6
769	184.0	153.2	82.7

Conclusions:

Results are considered relevant for describing the residence time and removal from Ge , introduced in a water column. Test conditions are chosen as realistic worst case. Notably, the test was performed at lower pH, which solubilises most metal.

Executive summary:

Removal from Ge after addition to a water column in the presence of a thin layer of natural sediment was measured over time. Test conditrions have not been standardised, but the medium was the OECD 29 T/D medium at the lower pH end (pH 6.0), at which highest solubilisation of Ge is expected.

The results demonstrate that Ge is removed from the water column to reach a level of 20% of original concentration after 28 days. Referring to the criterion of 70% removal after that period for organic substances, Ge and Ge-substances are considered to be "equivalent to rapidly degradable" in water.

Reference 2

Endpoint:

transformation / dissolution of metals and inorganic metal compounds

Type of information:

experimental study

Adequacy of study:

key study

Study period:

17 Jul 2019 - 20 Mar 2021

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)

Other quality assurance:

ISO/IEC 17025 (General requirements for the competence of testing and calibration laboratories)

Type of method:

flask method

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: Photonic Sense GmbH Am Goldberg 3 D-99817 Eisenach Germany ; Batch: 1913032
- Purity, including information on contaminants, isomers, etc.: 99.999 % (5N)

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Room temperature (20 - 23 °C), in the dark.
- Stability and homogeneity of the test material in the vehicle/solvent under test conditions (e.g. in the exposure medium) and during storage: Not indicated
- Stability in the medium, i.e. sensitivity of the test material to hydrolysis and/or photolysis: Not indicated
- Solubility and stability of the test material in the solvent/vehicle and the exposure medium: Not indicated
- Reactivity of the test material with the incubation material used (e.g. plastic ware): Not applicable

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing (e.g. warming, grinding): The test item, Germanium (powder), as received fulfilled the <1 mm size requirements. Therefore, there was no need for further preparation of the test item.
- Preliminary purification step (if any): No
- Final concentration of a dissolved solid, stock liquid or gel: Not applicable
- Final preparation of a solid (e.g. stock crystals ground to fine powder using a mortar and pestle): No

FORM AS APPLIED IN THE TEST (if different from that of starting material)
- Specify the relevant form characteristics if different from those in the starting material, such as state of aggregation, shape of particles or particle size distribution: Not applicable

OTHER SPECIFICS
- Other relevant information needed for characterising the tested material, e.g. if radiolabelled, adjustment of pH, osmolality and precipitate in the culture medium to which the test chemical is added: Form: Solid, (in the powder form) ; coulour: Grey ; particle size distribution: 100-300 mesh (i.e. 53-149 μm) ; particle size distribution: d10: 16.82 μm d50: 100.32 μm d90: 252.91 μm ; specific surface area: 0.129 m²/g ; homogenous ; density: 5.323 g/cm³

Key result

Type of test:

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

Mean dissolved conc.:

61.5 µg/L

Element analysed:

Germanium (powder)

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

Temperature: 21.2 - 22.9 °C
pH: 7.99 - 8.04.
Dissolved oxygen concentration: 8.27 - 8.46 mg/L O2.
Total organic carbon content (TOC): <1.0 mg/L C
Average germanium concentration of test medium at start of the test and blank control: 0.02 μg/L Ge

Key result

Type of test:

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

Mean dissolved conc.:

170 µg/L

Element analysed:

Germanium (powder)

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

Temperature: 21.2 - 22.9 °C
pH: 7.99 - 8.04.
Dissolved oxygen concentration: 8.27 - 8.46 mg/L O2.
Total organic carbon content (TOC): <1.0 mg/L C
Average germanium concentration of test medium at start of the test and blank control: 0.02 μg/L Ge

Details on results:

The following observations could be made in the test item vessels:
 Remaining, undissolved test item (grey powder particles) could be observed at the bottom of the test vessels at the end of the experiment. The test solutions were colourless.
 With a loading of 1 mg/L of Germanium (powder), the following amounts of germanium were measured during the test:
Average dissolved germanium concentrations (N = 9) of 61.5 ± 20.9 μg/L Ge at the 7 days and 170 ± 57 μg/L Ge at the 28 days sampling points were measured with a between-vessel variation of 34 % (N = 3) and 33 % (N = 3) respectively, which exceeded the <20 % quality criterion at the 7 and 28 days endpoints. The within-vessel coefficients of variation met the <10 % quality criterion for all test vessels at the 7 and 28 days endpoints.
Based on the specific surface area of Germanium (powder) (i.e. 0.129 m²/g test item), a germanium release per surface of 477 mg/m² and 1318 mg/m² was calculated at the 7 days and 28 days endpoints, respectively.
Based on the average germanium content in the test item (100 % Ge) and the average dissolved germanium concentration in the test solutions, a germanium release of 6.1 % and 17 % could be calculated at the 7 days and 28 days extraction endpoints.

Conclusions:

During this transformation/dissolution study on Germanium (powder) at a loading of 1 mg/L, it was shown that:
• For germanium, an average concentration of 61.5 μg/L Ge (CVoverall = 29 %; N = 9) was found after 7 days, and of 170 μg/L Ge (CVoverall = 29 %; N = 9) was found after 28 days of exposure to the standard medium at pH 8. The 7 days dissolution results corresponded with a germanium release of 6.1 % (or 477 mg/m²). The 28 days dissolution results corresponded with a germanium release of 17 % (or 1318 mg/m²).
The results can be assumed reliable since the test conditions stayed constant during the experiment.

Executive summary:

This study's objective was to obtain information about the dissolution characteristics of Germanium (powder) to classify metal-containing substances and mixtures according to the UN Globally Harmonized System, the EU Classification, Labelling and Packaging Regulation (Reg. 1272/2008 + amendment No 2018/669). Therefore, the OECD Test Guidance No. 29 (2001) was applied to determine the rate and pH-dependent extent of dissolution of Germanium (powder), tested with a target 1 mg/L loading in standard aqueous solutions at pH 8 for 28 days at an agitation speed of 100 revolutions per minute (rpm).

The short-term (acute) transformation/dissolution endpoint was based on the dissolved germanium concentrations obtained after 7 days. The long-term (chronic) transformation/dissolution endpoint was based on the dissolved germanium concentrations obtained after 28 days.
The study was performed at ECTX. Analyses of the concentrations of dissolved germanium and the determination of the total organic carbon content (TOC) of the test medium have been performed at WLN Business B.V. (The Netherlands), the ISO 17025 accredited laboratory, as delegated by ECTX.

The used test setup was designed by the Sponsor. It was based on the results of study X01-212 (7 days Transformation/Dissolution Study of Germanium Metal Powder at a 100 mg/L loading in a standard aqueous medium at pH 6 and pH 8.). As Germanium is light sensitive, extra measures were taken to exclude the influence of light as much as possible: the experiments were performed in the dark. The test vessels were wrapped with black plastic foil, and the preparation and sampling were carried out in diffuse red light.

All test parameter conditions were entirely following the OECD Test Guidance no.29 requirements:
• The medium's measured TOC was <1.0 mg/L C and below the required level of 2.0 mg/L C.
• The temperature of the test solutions fluctuated between 21.2 °C and 22.9 °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 item vessels during the test varied from 7.99 to 8.04. All measured data were within the specifications of pH 8 ± 0.2.
• The dissolved oxygen concentration measured in the blank and test item vessels at pH 8 varied from 8.27 to 8.46 mg/L O2. These values were higher than the required value of ± 6 mg/L O2 at 22 °C, corresponding to a minimum saturation level in the air of 70 %.
The test medium at the start of the test and the blank control vessels during the test showed small average concentrations of germanium above the limit of detection (0.02 μg/L Ge). The detection limit was determined as three times the standard deviations of the germanium measurements of all blank control samples in this study rounded up to one significant figure (N = 30).

During this study on Germanium (powder) at a loading of 1 mg/L to standard medium at pH 8, it was shown that:
The following average dissolved germanium concentrations were measured: 61.5 ± 18.1 μg/L Ge (CVoverall = 29 %; N = 9) and 170 ± 49 μg/L Ge (CVoverall = 29 %; N = 9) after 7 days and 28 days of exposure, respectively.
Based on the specific surface area of Germanium (powder) (i.e. 0.129 m²/g test item), a germanium release per surface of 477 mg/m² and 1318 mg/m² were calculated at the 7 days and 28 days endpoints, respectively.
Based on the average germanium content in the test item (100 % Ge) and the average dissolved germanium concentrations in the test solutions, a germanium release of 6.1 % and 17 % could be calculated at the 7 days and 28 days extraction endpoints.

Reference 3

Endpoint:

transformation / dissolution of metals and inorganic metal compounds

Type of information:

experimental study

Adequacy of study:

key study

Study period:

22 Jul 2019 - 20 Mar 2021

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)

Other quality assurance:

ISO/IEC 17025 (General requirements for the competence of testing and calibration laboratories)

Type of method:

flask method

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: PPM Pure Metals GmbH Am Bahnhof 1 D-38685 Langelsheim Germany ; batch: 1204
- Purity, including information on contaminants, isomers, etc.: purity: >99.999 % (5N)

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Room temperature (20 - 23 °C), in the dark.
- Stability and homogeneity of the test material in the vehicle/solvent under test conditions (e.g. in the exposure medium) and during storage: not specified
- Stability in the medium, i.e. sensitivity of the test material to hydrolysis and/or photolysis: not specified
- Solubility and stability of the test material in the solvent/vehicle and the exposure medium: not specified
- Reactivity of the test material with the incubation material used (e.g. plastic ware): not specified

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing (e.g. warming, grinding): The required loading of 1 mg/L is achieved by adding an appropriate amount of test medium to the actual exposed free metal surface after embedding (i.e. about 2.25 mm²/2 L).
- Preliminary purification step (if any): no
- Final concentration of a dissolved solid, stock liquid or gel: not applicable
- Final preparation of a solid (e.g. stock crystals ground to fine powder using a mortar and pestle): the samples of Ge were prepared by cutting, embedding and polishing.

FORM AS APPLIED IN THE TEST (if different from that of starting material)
- Specify the relevant form characteristics if different from those in the starting material, such as state of aggregation, shape of particles or particle size distribution: Solid, (in the massive form) ; Lumps 2-5 mm

OTHER SPECIFICS
- Other relevant information needed for characterising the tested material, e.g. if radiolabelled, adjustment of pH, osmolality and precipitate in the culture medium to which the test chemical is added: target surface area: 2.25 mm² ; Homogeneous ; density: 5.323 g/cm³

Key result

Type of test:

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

Mean dissolved conc.:

2.6 µg/L

Element analysed:

Ge

Loading of aqueous phase:

1 mg/L

Incubation duration:

26 d

Test conditions:

Temperature: 21.2 - 22.9 °C
pH: 7.98 - 8.04
Dissolved oxygen concentration: 8.27 - 8.46 mg/L O2
Total organic carbon content (TOC): <1.0 mg/L C
Average concentrations of germanium in test medium: 0.01 μg/L Ge

Key result

Type of test:

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

Mean dissolved conc.:

0.72 µg/L

Element analysed:

Ge

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

Temperature: 21.2 - 22.9 °C
pH: 7.98 - 8.04
Dissolved oxygen concentration: 8.27 - 8.46 mg/L O2
Total organic carbon content (TOC): <1.0 mg/L C
Average concentrations of germanium in test medium: 0.01 μg/L Ge

Details on results:

With a loading of 1 mg/L of Germanium (massive), the following amounts of germanium were measured during the test:
Average dissolved germanium concentrations (N = 9) of 0.72 ± 0.34 μg/L Ge at the 7 days and 2.60 ± 1.94 μg/L Ge at the 28 days sampling points were measured with a between-vessel variation of 47 % (N = 3) and 75 % (N = 3) respectively, which exceeded the <20 % quality criterion at the 7 and 28 days endpoints. The within-vessel coefficients of variation met the <10 % quality criterion for one test vessel at the 7 days sampling point.
Based on the specific surface area of Germanium (massive) (i.e. 2.21 mm² test item), a germanium release per surface of 643 mg/m² and 2311 mg/m² was calculated at the 7 days and 28 days endpoints, respectively.
Based on the average germanium content in the test item (100 % Ge) and the average dissolved germanium concentration in the test solutions, a germanium release of 0.072 % and 0.26 % could be calculated at the 7 days and 28 days extraction endpoints.

Conclusions:

During this transformation/dissolution study on Germanium (massive) at a loading of 1 mg/L, it was shown that:
• For germanium, an average concentration of 0.72 μg/L Ge (CVoverall = 41 %; N = 9) was found after 7 days, and 2.60 μg/L Ge (CVoverall = 65 %; N = 9) was found after 28 days of exposure to the standard medium at pH 8. The 7 days dissolution results corresponded with a germanium release of 0.072 % (or 643 mg/m²). The 28 days dissolution results corresponded with a germanium release of 0.26 % (or 2311 mg/m²).
• a highest (worst case) concentration of 1.11 μg/L Ge (CVwithin,2 = 2 %; N = 3) was found after 7 days, and 4.84 μg/L Ge (CVwithin,2 = 1 %; N = 3) after 28 days of exposure to the standard medium at pH 8 in the second test vessel. The 7 days dissolution results corresponded with a germanium release of 0.11 % (or 987 mg/m²). The 28 days dissolution results corresponded with a germanium release of 0.48 % (or 4302 mg/m²).
The results can be assumed reliable since the test conditions stayed constant during the experiment.

Executive summary:

This study's objective was to obtain information about the dissolution characteristics of Germanium (massive) to classify metal-containing substances and mixtures according to the UN Globally Harmonized System, the EU Classification, Labelling and Packaging Regulation (Reg. 1272/2008 + amendment No 2018/669). Therefore, the OECD Test Guidance No. 29 (2001) was applied to determine the rate and pH-dependent extent of dissolution of Germanium (massive), tested with a target 1 mg/L loading in standard aqueous solutions at pH 8 for 28 days at an agitation speed of 100 revolutions per minute (rpm).

The short-term (acute) transformation/dissolution endpoint was based on the dissolved germanium concentrations obtained after 7 days. The long-term (chronic) transformation/dissolution endpoint was based on the dissolved germanium concentrations obtained after 28 days. The study was performed at ECTX.

Analyses of the concentrations of dissolved germanium and the determination of the total organic carbon content (TOC) of the test medium have been performed at WLN Business B.V. (The Netherlands), the ISO 17025 accredited laboratory, as delegated by ECTX.

The used test setup was designed by the Sponsor. It was based on the results of study X01-212 (7 days Transformation/Dissolution Study of Germanium Metal Powder at a 100 mg/L loading in a standard aqueous medium at pH 6 and pH 8.). As Germanium is light sensitive, extra measures were taken to exclude the influence of light as much as possible: the experiments were performed in the dark. The test vessels were wrapped with black plastic foil, and the preparation and sampling were carried out in diffuse red light.

All test parameter conditions were entirely following the OECD Test Guidance no.29 requirements:
• The medium's measured TOC was <1.0 mg/L C and below the required level of 2.0 mg/L C.
• The temperature of the test solutions fluctuated between 21.2 °C and 22.9 °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 item vessels during the test varied from 7.98 to 8.04. All measured data were within the specifications of pH 8 ± 0.2.
• The dissolved oxygen concentration measured in the blank and test item vessels at pH 8 varied from 8.27 to 8.46 mg/L O2. These values were higher than the required value of ± 6 mg/L O2 at 22 °C, corresponding to a minimum saturation level in the air of 70 %.

The test medium at the start of the test, and the blank control vessels during the test showed small average concentrations of germanium above the limit of detection (0.01 μg/L Ge). The detection limit was determined as three times the standard deviations of the germanium measurements of all blank control samples in this study rounded up to one significant figure (N = 30).

During this study on Germanium (massive) at a loading of 1 mg/L (surface equivalent) to standard medium at pH 8, it was shown that:
The following average dissolved germanium concentrations were measured: 0.72 μg/L Ge (CVoverall = 41 %; N = 9) and 2.60 μg/L Ge (CVoverall = 65 %; N = 9) after 7 days and 28 days of exposure, respectively.
Based on the free surface area of Germanium (massive) (about 2.25 mm² test item per 2 litres of test medium), an average germanium release per surface of 643 mg/m² and 2311 mg/m² were calculated at the 7 days sampling point and 28 days endpoint, respectively.
Based on the average germanium content in the test item (100 % Ge) and the average dissolved germanium concentrations in the test solutions, a germanium release of 0.072 % and 0.26 % could be calculated at the 7 days and 28 days extraction endpoints.

Results based on the highest value (i.e. worst case):
The following average dissolved germanium concentration was measured in the worst case (second) test vessel: 1.11 μg/L Ge (CVwithin,2 = 2 %; N = 3) and 4.84 μg/L Ge (CVwithin,2 = 1 %; N = 3) after 7 days and 28 days of exposure, respectively.
Based on the free surface area of the Germanium (massive) sample in the second test vessel (2.45 mm² test item per 2178 mL of test medium), an average germanium release per surface of 987 mg/m² and 4302 mg/m² were calculated at the 7 days sampling point and 28 days endpoint, respectively.
Based on the germanium content in the test item (100 % Ge) and the average dissolved germanium concentrations in the worst case (second) test vessel, a germanium release of 0.11 % and 0.48 % could be calculated at the 7 days and 28 days extraction endpoints.

Description of key information

Transformation/dissolution (TD) testing was done at 2 pH (6 -8) on Ge-powder according to OECD 29.

-it was demonstrated that the TD was highest at pH 8, as compared to pH6.

-at pH 8 the TD after 7d was 0.0615 mg/L with 1mg/L loading of the substance

-at pH 8 the TD after 28d was 0.170 mg/L with 1mg/L loading of the substance

Key value for chemical safety assessment

Water solubility:

0.17 mg/L

at the temperature of:

21.5 °C

Additional information

The TD was documented highest at pH 8, as compared to pH 6 (ECTX 2017).

The solubility of germanium was defined with the transformation dissolution test. Results relate to 1mg/L loading of the substance over 28days.