Chromate(5-), bis[4-(hydroxy-κO)-7-[2-(2-hydroxy-1-naphthalenyl)diazenyl]-3-[2-[2-(hydroxy-κO)- 3-nitro-5-sulfophenyl]diazenyl]-2-naphthalenesulfonato(4-)]-, sodium (1:5)

Particle size distribution (Granulometry)

Link to relevant study record(s)

Reference

Endpoint:

particle size distribution (granulometry)

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 110 (Particle Size Distribution / Fibre Length and Diameter Distributions - Method A: Particle Size Distribution (effective hydrodynamic radius)

GLP compliance:

yes

Type of method:

other: sieve analysis and laser diffraction analysis

Mass median aerodynamic diameter:

ca. 12.8 µm

Key result

Percentile:

D50

Mean:

ca. 13 µm

Remarks on result:

other: result of laser diffraction analysis

Percentile:

D50

Mean:

> 250 µm

Remarks on result:

other: result of the sieve analysis

Visual investigation:

The test substance consisted of black clusters and agglomerates of various size. The shape of the particles was irregular. The diameter of the smallest and largest particles was approximately < 1 µm and > 1000 µm, respectively.

Microscopic inspection of the suspensions after 20 and 280 seconds showed, that the first one still contains a significant amount of agglomerates, whereas deagglomeration is nearly completed in the second. After sonication of the suspensions for 280 seconds, the suspensions were sonicated for another 180 seconds with a high power sonication bath. The results of these measurements were almost equal to the measurements after 280 seconds of sonication.

Determination of the dispersability of the test substance:

In water, the test substance dissolved completely.

In ethanol, the test substance dissolved partially.

In cyclohexane, no visible dissolving was observed.

As a result of the tests, cyclohexane was chosen as test medium.

Sieve analysis:

The results of the sieve analysis are:

< 63 µm:  20.4 % (w/w)

63 - 250 µm:  25.0 % (w/w)

> 250 µm  54.6 % (w/w)

Laser Diffraction Analysis:

The results of the measurements after 280 seconds of sonication were used to calculate the mean values. From these results the particle size distribution was determined to be:

< 2 µm: 0.1 % (w/w)

2- 5 µm: 8.5 % (w/w)

5-10 µm: 27.5 % (w/w)

10-20 µm: 38.5 % (w/w)

20-50 µm: 22.6 % (w/w)

50-63 µm: 1.5 % (w/w)

>63 µm: 1.3 % (w/w)

Conclusions:

Mass Median Diameter value: 13 µm

Executive summary:

The particle size distribution of the test item was evaluate according to the OECD guideline 110. The test substance was analysed by visual inspection with microscope, sieve analysis and laser light diffraction method. Visual investigation showed that the shape of the particles was irregular. The results of the sieve analysis showed a diameter > 250 µm for 54.6 % (w/w). Laser Diffraction Analysis carried out after 280 seconds of ultrasonic treatment showed a D50 of 13 µm.

As sieve analysis cannot be used to determine the MMAD (diameter used in the assessment of the level of deposition in regions of the respiratory tract), the Laser Diffraction Analysis results are considered more relevant. In addition, by comparing the sieve analysis with the Laser Diffraction Analysis results and using the worst case approach, a D50 of 13 µm is used.

Description of key information

D50 = 13 µm

Additional information

The particle size distribution of the test item was evaluate according to the OECD guideline 110. The test substance was analysed by visual inspection with microscope, sieve analysis and laser light diffraction method. Visual investigation showed that the shape of the particles was irregular. The results of the sieve analysis showed a diameter > 250 µm for 54.6 % (w/w). Laser Diffraction Analysis carried out after 280 seconds of ultrasonic treatment showed a D50 of 13 µm.

As sieve analysis cannot be used to determine the MMAD (diameter used in the assessment of the level of deposition in regions of the respiratory tract), the Laser Diffraction Analysis results are considered more relevant. In addition, by comparing the sieve analysis with the Laser Diffraction Analysis results and using the worst case approach, a D50 of 13 µm is used.