Cesium tungsten oxide

Particle size distribution (Granulometry)

Administrative data

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

particle size distribution (granulometry)

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

01 Dec 2016 - 15 Feb 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

GLP guideline study

Qualifier:

according to guideline

Guideline:

other: European Commission Technical Guidance Document EUR 20268 Determination of Particle Size Distribution, Fibre Length and Diameter Distribution of Chemical Substances

Version / remarks:

adopted in 2002

GLP compliance:

yes (incl. QA statement)

Remarks:

Department of Health, London, UK

Type of method:

cascade impaction

Type of particle tested:

aggregate

Type of distribution:

volumetric distribution

Size:

< 100 µm

Distribution:

78.4 %

Remarks on result:

other: Sieve Method

Size:

< 10 µm

Distribution:

<= 0.87 %

Remarks on result:

other: Cascade impactor method

Size:

< 5.5 µm

Distribution:

< 0.1 %

Remarks on result:

other: Cascade impactor method

Results
Sieve Screening Test
The results of the sieving procedure are shown in the Table 2:

Table 2

Measurement	Result
Mass of test item transferred to sieve	10.21 g
Mass of test item passed through sieve	8.00 g
Percentage of test item less than 100μm	78.4%

 

Cascade Impactor
The results of the cascade impactor procedure are shown in Table 3:

Table 3

			Collected mass (g)		Collected mass (g)		Collected mass (g)
Collection stage	Particle size range collected (μm)		Determination 1		Determination 2		Determination 3
Artificial throat		n/a		0.06		0.15		0.04
Cup 1		>10.0		2.9526		2.9260		3.1398
Cup 2		5.5 to 10.0		0.0234		0.0194		0.0057
Cup 3		2.4 to 5.5		0.0024		0.0008		0.0000*
Cup 4		1.61 to 2.4		0.0005		0.0003		0.0007
Cup 5		0.307 to 1.61		0.0001		0.0000		0.0000*
Final filter		<0.307		0.0000		0.0001		0.0000
		Total mass of collected test item		3.0390		3.0966		3.1862
		Mass of test item added		3.0646		3.1528		3.3034

* Actual cup masses showed a minor apparent mass loss during these two measurements; however these values (≤ 0.0005 g) were considered both insignificant and negligible, and as such, considered within the repeatability tolerance of the balance used. A zero mass change has been used for cumulative test item mass calculations to prevent underestimation of the fine particle size fraction of the test item.

The cumulative amounts of test item collected in the three determinations for the individual particle size cut-points are shown in Table 4.

Table 4

	Cumulative mass			Cumulative percentage [%]
Particle size cut point [µm]	Det.1	Det. 2	Det. 3	Det.1	Det. 2	Det. 3
<10.0	0.0264	0.0206	0.0064	0.87	0.67	0.20
<5.5	0.0030	0.0012	0.0007	<0.1	<0.1	<0.1
<2.4	0.0006	0.0004	0.0007	<0.1	<0.1	<0.1
<1.61	0.0001	0.0001	0.0000	<0.1	<0.1	<0.1
<0.307	0.0000	0.0001	0.0000	<0.1	<0.1	<0.1

 

Overall cumulative percentage with a particle size less than 10.0μm: ≤ 0.87%

Mean cumulative percentage with a particle size less than 5.5μm: < 0.1%

Discussion
Sampling for the cascade impactor determinations was performed by rolling the test item container for approximately 10 minutes then sampled from the top, middle and bottom. The overall results from the cascade impactor were taken as limit values due to the variation between the sampling positions; this gives a worst case scenario.

Too few particles were of a size less than 10.0μm to allow accurate assessment of the mass median aerodynamic diameter.

The inhalable fraction is defined as the mass fraction of particles which can be inhaled by nose or mouth, the thoracic fraction is defined as the mass fraction of particles that passes the larynx and the respirable fraction is defined as the mass fraction of particles that reaches the alveoli.

 

Conclusion

Particle size data acquired for the test item is shown in Table 5.

Table 5

Measurement	Method	Result
Percentage of test item with an inhalable particle size < 100μm	Sieve	78.4%
Percentage of test item with a thoracic particle size < 10.0μm	Cascade impactor	≤ 0.87%
Percentage of test item with a respirable particle size < 5.5μm	Cascade impactor	< 0.1%

Conclusions:

The nanoform of cesium tungsten trioxide rapidly agglomerates/aggregates upon drying after being suspended in water. The aggregates were mainly ≥ 10 µm ≤ 100 µm (> 79 %), with a small fraction (< 0.1 %) smaller than 5.5 µm.

Executive summary:

During a particle size analysis using the seive/cascade impaction method used to determine particle size it was seen that the nanoform of cesium tungsten trioxide rapidly agglomerates/aggregates upon drying after being suspended in water.

This was shown by the results of this experiment whereby the sizes measured where mostly in the micrometre range. The aggregates were mainly ≥ 10 µm ≤ 100 µm (> 79 %), with a small fraction (< 0.1 %) smaller than 5.5 µm. The small fraction is below 5.5 µm is likely accounted for by unaggregated material (single nanoform particles).

Reference 2

Endpoint:

particle size distribution (granulometry)

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Qualifier:

equivalent or similar to guideline

Guideline:

other: JRC Identification of nanomaterials through measurements

Version / remarks:

2019

Deviations:

not applicable

Qualifier:

equivalent or similar to guideline

Guideline:

other: Appendix for nanoforms applicable to the Guidance on Registration and Substance Identification, ECHA

Version / remarks:

2019

Deviations:

not applicable

Qualifier:

according to guideline

Guideline:

other: Preparation of nanoparticles by cup horn sonication

Version / remarks:

version number 2.0, 14.07.2017 of the ERANET-SIINN Project NanoToxClass

Deviations:

no

Qualifier:

equivalent or similar to guideline

Guideline:

other: An overview of concepts and terms used in the European Commission’s definition of nanomaterial, JRC

Version / remarks:

2019

Deviations:

not applicable

Principles of method if other than guideline:

Not applicable.

Type of method:

microscopic examination

Remarks:

High-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) in combination with energy-dispersive X-ray spectroscopy (EDXS).

Type of particle tested:

primary particle

Type of distribution:

counted distribution

Remarks on result:

other: size is based on direct measurement of particles on a TEM grid.

Key result

Percentile:

D50

Mean:

10.3 nm

Remarks on result:

other: d50 represents a median not mean value based on a number based size distribution. D50 is based on 760 individual particle diameter measurements.

Key result

Percentile:

D10

Mean:

5 nm

Remarks on result:

other: d10 is not a mean value but is based on a number based size distribution (percentile). D10 is based on 760 individual particle diameter measurements.

Key result

Percentile:

D90

Mean:

22.5 nm

Remarks on result:

other: d90 represents a median not mean value based on a number based size distribution. D90 is based on 760 individual particle diameter measurements.

Description of key information

The material was confirmed to be a nanoform in the spheroidal category with 100 % of particles measuring 1-100 nm, and have a D10, D50 and D90 of 5.0 nm, 10.3 nm and 22.5 nm, respectively, Rosenfeldt, 2020.