Barium 4-[(5-chloro-4-methyl-2-sulphonatophenyl)azo]-3-hydroxy-2-naphthoate

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:

2020

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 “unstable” in 10 mM Ca, representing high water hardness.

After 6h, the samples showed high dispersion stability in 0 mM Ca and at pH 9 in 1 mM Ca. Stability at all other conditions was either intermediate (pH 4 and 7 in 1 mM Ca) or low (all samples in 10 mM Ca).

After 24 hoursthe stability for samplesin 0 mM Ca at pH 7 and 9 was high. For the samples at pH 4 in 0 mM Ca and at pH 9 in 1 mM Ca the stability was intermediate. The stability at all other conditions 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	98.8	0.4	94.7	1.5	86.6	2.9
pH 4	1	34.6	6.9	12.5	3.9	7.7	2.0
pH 4	10	6.5	1.2	3.5	0.2	2.8	0.3
.
pH 7	0	99.7	0.2	97.7	0.7	95.8	1.6
pH 7	1	17.9	1.2	5.8	0.5	3.0	0.2
pH 7	10	5.6	0.4	2.0	0.4	1.2	0.4
.
pH 9	0	99.9	0.8	99.2	1.1	97.9	0.3
pH 9	1	100.0	0.1	65.1	8.5	46.4	4.9
pH 9	10	5.2	0.1	2.2	0.0	1.6	0.0

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 (SOP AUC-RI). The centrifugation parameters are given in the methods section.

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 0.031.This is a fraction of 2.1% of the initial absorption, but actually is close to the LOD of the built-in UV/Vis detector. Considering the LOD, between 0% and 2.1% of the sample may have been dissolved.

All evidence combined, the results after centrifugation confirm that at least 97.9% of the observed dispersion stability has to be attributed to the particles, not to dissolution.

Executive summary:

The dispersion stability of Pigment Red 48:1 depends especially on pH and water hardness. In 0 mM Ca at pH 7 and 9 the stability was high. At pH 4 in 0 mM Ca and at pH 9 in 1 mM Ca the stability was intermediate. The stability at all other conditions was low

Cross-reference 2

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:

2008

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Qualifier:

equivalent or similar to guideline

Guideline:

other: OECD Guideline 105 and ETAD method

Principles of method if other than guideline:

To measure the partition coefficient of pigments utilising the standard OECD Guideline 107 is extremely difficult because of the problems associated with the inherent very low solubilities. The following procedure is used for determining the LogPow of low solubility substances and in particular that of pigments.
The partition coefficient was estimated based on the ratio of the solubilities in n-octanol and in water. The individual solubilities were determined by flask method based on OECD Guideline 105 and the ETAD method.

A defined amount of the pigment (see table 1) was transferred to a 100 ml flask with glass stopper and 60 ml of water (deionised, 18.2 MOcm). This was stirred at 70°C for 2 hours, and then 72 hours in an air conditioned laboratory (T = 23°C). The suspension was then centrifuged (10 000 rpm, 10 min) and filtered once through a standard paper filter, twice through a 0.2 μm membrane filter (Millipore) and twice through a 0.025μm membrane filter (Millipore). If particles were detected in the solution (turbidity), the final filtration step was repeated until a perfectly clear solution was acheived.
The above procedure was conducted in parallel for a total of 2 water (deionised, 18.2 MOcm) samples and of 2 n-octanol (Sigma-Aldrich, spectrophotometric grade) samples.

GLP compliance:

no

Type of method:

shake-flask method to: flask method

Partition coefficient type:

octanol-water

Specific details on test material used for the study:

- Name of test material (as cited in study report): PIGMENT RED 48:1, PIGMENT RED 48:1, lab sample (non-resin coated), TK 10318
- Analytical purity: 94.3% w/w
- Substance type: Organic
- Physical state: Solid (powder)
- Lot/batch No.: DMG6708
- Expiration date of the lot/batch: January 01st, 2017

Analytical method:

high-performance liquid chromatography

other: UV/Vis

Key result

Type:

log Pow

Partition coefficient:

> 0.11

Temp.:

23 °C

Remarks on result:

other: The pH was not reported.

Details on results:

Solubility in n-octanol: 31-33 µg/L UV/Vis)
Solubility in water: < 25 µg/L (HPLC-DAD)
Weight in n-octanol/water: 54.2-56.8 mg/100mL

Conclusions:

The partition coefficient of test substance was estimated to be log Pow= >0.11 at 23°C.