Registration Dossier

Administrative data

Endpoint:
adsorption / desorption: screening
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
the study does not need to be conducted because the physicochemical properties of the substance indicate that it can be expected to have a low potential for adsorption
Justification for type of information:
JUSTIFICATION FOR DATA WAIVING
see attached justification
Cross-referenceopen allclose all
Reason / purpose:
data waiving: supporting information
Remarks:
dispersion stability
Reference
Endpoint:
additional information on environmental fate and behaviour
Remarks:
Dispersion stability in simulated environmental media
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
Qualifier:
according to
Guideline:
other: OECD 318
GLP compliance:
no

At any of the time points mentioned in the TG-318, the influence of Ca is critical. Regardless of pH, the pigment is categorized at the 24h-sampling time as “unstable” in 10 mM Ca, representing high water hardness.

After 6h, regardless of pH, the samples showed high dispersion stability in 0 an 1 mM Ca.

After 24 hours the stability for these samples became intermediate. For the samples in 10 mM 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

93.2

0.3

81.0

2.6

73.5

3.0

pH 4

1

94.2

0.5

84.5

2.2

73.0

4.5

pH 4

10

11.9

3.0

4.5

1.2

2.8

1.2

.

 

 

 

 

 

 

pH 7

0

95.0

1.8

88.3

4.5

80.2

4.7

pH 7

1

95.9

1.9

88.8

4.4

72.3

7.4

pH 7

10

8.6

0.4

3.4

0.2

2.3

0.1

.

 

 

 

 

 

 

pH 9

0

93.3

1.0

86.8

1.7

81.6

0.9

pH 9

1

97.8

1.5

89.7

3.8

66.3

4.5

pH 9

10

10.5

0.5

4.5

0.4

3.1

0.3

To rationalize the observed dispersion stability, we finally checked the particle size distribution directly in the environmental medium (exact same sample preparation as for the UV/VIS measurements). We applied the NanoDefine method of Analytical Ultracentrifugation.

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 c.a 0.05. This is a fraction of 3.5% of the initial absorption, but actually is close to the LOD of the built-in UV/Vis detector. Considering the LOD, between 0% and 3.5% of the sample may have been dissolved.

 

All evidence combined, the results after centrifugation confirm that at least 96.5% of the observed dispersion stability has to be attributed to the particles, not to dissolution.

Executive summary:

Elevated apparent dispersion stability may originate from dissolution. The dissolution in environmental media has not yet been assessed, but the particle size distribution was measured in all media. The remaining absorption after centrifugal separation of particles was determined to be not more than 3.6% of the total signal. Thus, dissolution is not the main cause of the observed stability.

 

Taken together, the dispersion stability of Pigment Yellow 95 depends especially on water hardness. Regardless of pH, the stability in 0 and 1 mM Ca is high, in 10 mM Ca the stability is low.

Reason / purpose:
data waiving: supporting information
Remarks:
disperions stability
Reference

see endpoint study record in chapter 5.6

Reason / purpose:
data waiving: supporting information
Remarks:
dispersion stability
Reference

The dispersion stability of Pigment Yellow 95 was strongly depended on water hardness. Dissolution was excluded as the main cause of the apparent stability. Regardless of pH, the stability in 0 and 1 mM Ca(NO3)2 was high, in 10 mM Ca(NO3)2 the stability was low.

→ Details refer to the endpoint 5.7

The OECD TG 318 on Dispersion Stability of Nanomaterials in Simulated Environmental Media is the first nano-specific test guideline, published 2017. Here we applied it to an organic pigment in order to map the ranges of stability in different media of surface water.

→ The study record maintained at the endpoint 5.7

Reason / purpose:
data waiving: supporting information
Remarks:
logKow
Reference

Estîmated based on solubility ratio:

log Pow= 0 at 23°C

Log Kow (Log Pow):
0
at the temperature of:
20 °C

The Log Pow was determined following the ETAD guideline ETAD-299 based on the water solubility method OECD 105.

The test substance is almost insoluble in water as well as in n-Octanol therefore it is not possible to determine the log Pow experimentally by the shake flask method nor by HPLC method.

Reason / purpose:
data waiving: supporting information
Remarks:
logKow
Reference
Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2011
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
test procedure in accordance with national standard methods with acceptable restrictions
Qualifier:
according to
Guideline:
other: ETAD guideline ETAD-299 based on the water solubility method OECD 105
Principles of method if other than guideline:
calculation based on the individual solubility in water and n-octanol
GLP compliance:
no
Type of method:
estimation method (solubility ratio)
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
Key result
Type:
log Pow
Partition coefficient:
0
Temp.:
23 °C
Remarks on result:
other: no data on pH
Details on results:
3 independent vials from each solubility test were injected and measured. Each result given is the average of these 3 measurements.
Water solubility test: 50 µg/L
n-Octanol solubility test: 50 µg/L
None of the signal due to the pigment Yellow 95 could be observed in the solubility tests.

Estimation based on solubility ratio:

Pow= C(n-octanol) / C(water)= 50 µg/L / 50 µg/L = 1

log Pow= 0

Conclusions:
The partition coefficient of test substance was estimated to be log Pow= 0 at 23°C based on solubility ratio.

Data source

Materials and methods

Results and discussion

Applicant's summary and conclusion