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EC number: 252-525-1 | CAS number: 35355-77-2 This substance is identified in the Colour Index by Colour Index Constitution Number, C.I. 15880:2.
Additional information on environmental fate and behaviour
Administrative data
- Endpoint:
- additional information on environmental fate and behaviour
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 2020
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- guideline study
Data source
Reference
- Reference Type:
- study report
- Title:
- Unnamed
- Year:
- 2 020
- Report date:
- 2020
Materials and methods
Test guideline
- Qualifier:
- according to guideline
- Guideline:
- other: OECD 318
- GLP compliance:
- no
Test material
- Reference substance name:
- Manganese, 3-hydroxy-4-[(1-sulfo-2-naphthalenyl)azo]-2-naphthalenecarboxylic acid complex
- EC Number:
- 252-525-1
- EC Name:
- Manganese, 3-hydroxy-4-[(1-sulfo-2-naphthalenyl)azo]-2-naphthalenecarboxylic acid complex
- Cas Number:
- 35355-77-2
- Molecular formula:
- C21H12MnN2O6S
- IUPAC Name:
- manganese(2+) hydrogen 3-oxido-4-[(E)-(1-sulfonatonaphthalen-2-yl)diazenyl]naphthalene-2-carboxylate
- Test material form:
- solid: nanoform
Constituent 1
Results and discussion
Any other information on results incl. tables
It should be mentioned that for the samples in 0 mM Ca we observed a strong flocculation and partial deposition of pigment on the tube walls. This led to the potential overestimation of the sample stability. As it was difficult to deduce to which extent the sample was agglomerated visually, the stability was not rated for these samples.
After 6h, the samples showed intermediate dispersion stability at all evaluated conditions. After 24 hours the stability in 1 mM Ca at pH 9 remained intermediate. For the samples at all other evaluated conditions the stability was low
Full results of the dispersion stability in the presence of NOM
Ca(NO3)2 | Stability after 6h | Standard deviation | Stability after 15h | Standard deviation | Stability after 24h | Standard deviation | |
[mM] | [%] | [%] | [%] | [%] | [%] | [%] | |
|
|
|
| ||||
pH 4 | 0 | - | - | - | - | - | - |
pH 4 | 1 | 41.0 | 5.1 | 11.5 | 0.9 | 8.0 | 0.6 |
pH 4 | 10 | 19.1 | 1.2 | 8.9 | 0.8 | 5.7 | 2.2 |
. |
|
|
|
|
|
| |
pH 7 | 0 | - | - | - | - | - | - |
pH 7 | 1 | 27.5 | 0.2 | 5.7 | 1.6 | 4.1 | 1.3 |
pH 7 | 10 | 14.0 | 2.2 | 3.4 | 0.3 | 7.3 | 1.1 |
. |
|
|
|
|
|
| |
pH 9 | 0 | - | - | - | - | - | - |
pH 9 | 1 | 95.6 | 1.0 | 79.4 | 2.8 | 46.3 | 3.5 |
pH 9 | 10 | 16.8 | 0.9 | 7.6 | 0.3 | 5.8 | 0.3 |
To rationalize the observed dispersion stability, we finally checked the particle size distribution directly in the environmental medium. We applied the NanoDefine method of Analytical Ultracentrifugation. The centrifugation parameters are given in the methods section.
As required by TG318, paragraph 31, the tested nanomaterial was pre-wetted in ultrapure water and left in the form of wet-paste for 24 h. The TG318 requires this step “to insure the proper interaction of nanomaterial surface with ultrapure water.” We visually observed incomplete wetting, and so any ensuing measurement would have been incorrect. In accord with the NanoGenoTox dispersion protocol, a drop of ethanol was added, successfully transferred the powder into a paste, which was then further diluted as specified in the TG318
The observed size distributions confirm the moderate agglomeration at 1 mM Ca, pH7, with NOM. If the particles would have been significantly dissolved, no size distribution would be observable at all by this method, which relies on the detection of the movement of particles during centrifugal separation.
Additionally, the centrifugation methods include a determination of the remaining absorption after centrifugation, fully consistent with the conventional determination of the dissolved fraction after centrifugation as recommended by the TG-318. The remaining absorption was measured at ca. 0.09. This is a fraction of 7% of the initial absorption, but actually is close to the LOD of the built-in UV/Vis detector. Considering the LOD, between 0% and 7% of the sample may have been dissolved.
All evidence combined, the results after centrifugation confirm that at least 93% of the observed dispersion stability has to be attributed to the particles, not to dissolution.
Applicant's summary and conclusion
- Executive summary:
After 6h, the samples showed intermediate dispersion stability at all evaluated conditions. After 24 hours the stability in 1 mM Ca at pH 9 remained intermediate. For the samples at all other evaluated conditions the stability was low
Samples for 0 mM Ca were not evaluated due to strong flocculation and partial deopsition of pigment on the tube walls.
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