Barium bis[2-chloro-5-[(2-hydroxy-1-naphthyl)azo]toluene-4-sulphonate]

Adsorption / desorption

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-reference

Cross-reference 1

Reason / purpose for cross-reference:

data waiving: supporting information

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:

2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: OECD 318

GLP compliance:

yes (incl. QA statement)

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 “instable” in 10 mM Ca, representing high water hardness. At 6h, most media induce “intermediate stability”, and only one medium (0 mM Ca, pH 9) induces a stability above 90%. At 24h, all media at 0 mM Ca and 1 mM Ca induce an intermediate stability between 60% and 87%. The stabilities systematically decrease over time, decrease slightly between 0 mM Ca and 1 mM Ca. The difference between pH 4 and pH 7 is low, but pH 9 systematically induces a slightly higher stability.

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	84.2	0.7	75.3	1.2	64.5	1.1
pH 4	1	81.9	0.4	70.3	0.7	60.3	0.6
pH 4	10	9.0	0.8	3.3	0.6	2.3	0.5
pH 7	0	80.3	0.6	70.6	0.3	63.4	0.6
pH 7	1	81.3	0.7	69.9	0.0	62.0	0.5
pH 7	10	9.7	0.9	4.1	0.2	3.2	0.2
pH 9	0	93.8	0.6	90.0	1.3	86.7	1.6
pH 9	1	86.9	0.5	75.2	1.8	69.3	1.3
pH 9	10	10.6	0.2	5.9	0.3	4.5	0.4

 

 

The results showed that under NOM-free conditions, the pigment was minimally less stable.The differences are not statistically significant.

 

Table 2: Comparison of the results of the dispersion stability with and without the presence of NOM

sedimentation time	6h	24h
1mM Ca, pH7, with NOM	99.45±0.39	99.22 ± 0.05
1mM Ca, pH7, without NOM	99.67 ± 0.02	98.81 ± 0.29

 

To rationalize the observed dispersion stability, the particle size distribution directly in the environmental medium (exact same sample preparation as for the UV/VIS measurements) was checked.

The NanoDefine method of Analytical Ultracentrifugation (SOP AUC-RI, published by 3) was applied. The centrifugation parameters are given above.

The observed size distributions confirm the low agglomeration at 0 mM and 1 mM Ca, against the high agglomeration at 10 mM Ca.

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. Even for the case of highest stability (pH 9, 0 mM Ca, with NOM), the remaining absorption was measured at 0.0504 ± 0.0024. This is a fraction of 2% of the initial absorption, but actually is close to the LOD of the built-in UV/Vis detector. Considering the LOD, between 0% and 2% of the sample may have been dissolved.

All evidence combined, the results after centrifugation confirm that at least 98% of the observed dispersion stability has to be attributed to the particles, not to dissolution.

Executive summary:

We found that the organic pigment is rather insensitive to pH changes, with little differences in dispersion stability between pH 4 and pH 9.

This is a significant difference against the metal oxide (TiO2) that was proposed as benchmark material of “intermediate stability” by the TG318.

Dissolution was excluded as the main cause of the apparent stability. The dispersion stability of Pigment Red 53:1 is of “intermediate stability” and depends especially on water hardness.

Only in very hard water with 10mM Ca, the stability of “low”. In all other conditions, the stability is at least “intermediate”, such that the aquatic compartment is relevant to risk assessment.

Cross-reference 2

Reason / purpose for cross-reference:

data waiving: supporting information

Cross-reference 3

Reason / purpose for cross-reference:

data waiving: supporting information

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:

comparable to guideline study with acceptable restrictions

Principles of method if other than guideline:

The partition coefficient was estimated based on the ratio of the solubilities in n-octanol and in water.
The individual solubilities were determined by the flask method based on OECD Guideline 105 and the ETAD method. The quantification was analyzed by HPLC-UV.

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:

-0.62

Temp.:

23 °C

Remarks on result:

other: measured immediately after filtration

Key result

Type:

log Pow

Partition coefficient:

1.69

Temp.:

23 °C

Remarks on result:

other: measured after one week

The pigment-solutions were not stable. After ca. one week an agglomeration of the pigment can be observed (especially in water). So there are two different results given for this pigment.

One measurement was made immediately after filtraton of the pigment. The clear solution was injected in the HPLC. The second measurement was made after one week. The solution shows an agglomeration of the pigment. This pigment was filtrated again and the clear solution was injected in the HPLC.

Conclusions:

The partition coefficient of test substance was estimated as follows:
- measured immediately after filtration: log Pow= -0.62 at 23°C
- measured after one week: log Pow= 1.69 at 23°C

Cross-reference 4

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Endpoint:

partition coefficient

Type of information:

calculation (if not (Q)SAR)

Remarks:

Migrated phrase: estimated by calculation

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Principles of method if other than guideline:

Leo and Hansch (1995)

GLP compliance:

no

Type of method:

other: calculated

Partition coefficient type:

octanol-water

Type:

log Pow

Partition coefficient:

-0.56

Temp.:

25 °C

Remarks on result:

other: pH value not available