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Environmental fate & pathways

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:
2021
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2021
Report date:
2021

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
other: OECD 318
GLP compliance:
yes (incl. QA statement)

Test material

Constituent 1
Chemical structure
Reference substance name:
4,11-dichloro-5,12-dihydroquino[2,3-b]acridine-7,14-dione
EC Number:
221-423-9
EC Name:
4,11-dichloro-5,12-dihydroquino[2,3-b]acridine-7,14-dione
Cas Number:
3089-16-5
Molecular formula:
C20H10Cl2N2O2
IUPAC Name:
4,11-dichloro-5,12-dihydroquino[2,3-b]acridine-7,14-dione
Test material form:
solid: nanoform, no surface treatment
Details on test material:
- Batch 200389
- State of aggregation: solid, powder
- The number-based concentration of particles with sizes below 100 nm (smallest feret diameter) is 99%
- Particle size distribution (TEM): 43.3 nm (D50)
- Shape of particles: multimodal/orthorhombic
- Coating: no
- Surface properties: not applicable
- Density: 1689 kg/m³ at 20°C
- Moisture content: refer to IUCLID chapter 1
- Residual solvent: refer to IUCLID chapter 1
- Activation: not applicable
- Stabilisation: not applicable

Test material purity is 100% pigment minus extractables and volatiles

Results and discussion

Any other information on results incl. tables

At any of the time points mentioned in the TG-318, the influence of Ca is critical. Regardless of pH, the pigment is least stable in 10 mM Ca, representing high water hardness. After 6h, the samples showed high dispersion stability in 0 mM Ca and intermediate stability at all other conditions. After 24 hours the stability in 0 mM Ca at pH 9 remained high. The stability at pH 7 was intermediate. For the samples at all other conditions the stability was low.


Table 1: 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



99.5



2.5



81.2



3.9



6.2



0.5



pH 4



1



34.3



0.8



13.2



0.7



4.1



0.4



pH 4



10



20.9



1.2



10.4



0.6



7.6



0.5



.


 

 



 



 



 



 



 



pH 7



0



99.7



1.1



99.3



1.3



13.0



2.9



pH 7



1



29.9



0.9



11.6



2.2



10.8



0.6



pH 7



10



20.1



0.6



7.1



0.5



9.6



0.6



.


 

 



 



 



 



 



 



pH 9



0



101.0



1.0



101.3



0.8



100.9



1.1



pH 9



1



11.5



0.5



5.4



1.0



3.7



1.0



pH 9



10



9.9



0.6



5.4



0.3



4.5



0.1



 


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 (SOP AUC-RI, published by 3). 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 (Figure 4). 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. 0.06. This is a fraction of 3% of the initial absorption, but actually is close to the LOD of the built-in UV/Vis detector. Considering the LOD, between 0% and 3% of the sample may have been dissolved.


All evidence combined, the results after centrifugation confirm that at least 97% of the observed dispersion stability has to be attributed to the particles, not to dissolution.

Applicant's summary and conclusion

Conclusions:
At any of the time points mentioned in the TG-318, the influence of Ca is critical. Regardless of pH, the pigment is least stable in 10 mM Ca, representing high water hardness.
After 6h, the samples showed high dispersion stability in 0 mM Ca and intermediate stability at all other conditions.
After 24 hours the stability in 0 mM Ca at pH 9 remained high. The stability at pH 7 was intermediate. For the samples at all other conditions the stability was low.
Taken together, the dispersion stability of 4,11-DQA depends on pH and water hardness. The stability in 0 mM Ca at pH 9 is high. The stability at pH 7 is intermediate regardless Ca concentration. For the samples at all other conditions the stability is low.