Perylene-3,4:9,10-tetracarboxydiimide

Additional information on environmental fate and behaviour

Administrative data

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

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2020

Report date:

2019

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: OECD 318

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Perylene-3,4:9,10-tetracarboxydiimide

EC Number:

201-344-6

EC Name:

Perylene-3,4:9,10-tetracarboxydiimide

Cas Number:

81-33-4

Molecular formula:

C24H10N2O4

IUPAC Name:

7,18-diazaheptacyclo[14.6.2.2²,⁵.0³,¹².0⁴,⁹.0¹³,²³.0²⁰,²⁴]hexacosa-1(23),2,4,9,11,13,15,20(24),21,25-decaene-6,8,17,19-tetrone

Test material form:

solid: particulate/powder

Details on test material:

-

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 categorized at the 24h-sampling time as “unstable” in 10 mM Ca, representing high water hardness. At 6h, most media induce “intermediate stability”, only at 10mM Ca we observed “low stability”.

The difference between pH 7 and pH 9 is low, but pH 4 systematically induces a lower 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	21.8	1.3	11	1.1	7.7	0.4
pH 4	1	12.3	0.7	6.2	0.5	5.1	0.5
pH 4	10	7.5	0.6	3.4	0.1	2.4	0.2
.
pH 7	0	41.8	2.3	22.1	1.4	17.1	1
pH 7	1	39.9	2	18.8	0.8	15.1	0.2
pH 7	10	9.6	0.5	4.4	0.4	3.4	0.3
.
pH 9	0	31.9	1.5	21	1.1	16.1	1.1
pH 9	1	29	2	20	0.4	15.7	0.6
pH 9	10	8	0.2	4.3	0.3	3.2	0.2

 

Comparing dispersion stability without NOM

The core hypothesis of the present study was that Pigment Violet 29, due to its hydrophobicity, might be categorized as “low dispersion stability”, under all conditions. This was proven wrong by the testing in the presence of NOM. Testing under NOM-free conditions was thus obsolete and not performed.

Cross-check the apparent stability by a fractionating method that physically separates particles from dissolved matter, and centrifugation results

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 distribution is very polydisperse, with a fraction of particle agglomerates at 200nm, which are responsible for the intermediate stability. 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.

Applicant's summary and conclusion

Executive summary:

The evidence from dispersion stability is consistent with the size distribution obtained by centrifugal separation of particles. The pigment Violet 29 is significantly agglomerated, but above the 10% stability cutoff after 6h.

We found that the organic pigment is rather insensitive to pH changes, with limited differences in dispersion stability between pH 4 and pH 9. This was a significant difference against the metal oxide (TiO2) that was proposed as benchmark material of intermediate stability by the TG-318.

Taken together, the dispersion stability of Pigment Violet 29 is intermediate in media with NOM. Only in very hard water with 10 mM Ca, the dispersion stability is low.