Willow, Salix alba, ext.

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

Study period:

2019-01-28 to 2019-02-18

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

ISO 13320 (Particle size analysis - Laser diffraction methods)

Version / remarks:

ISO13320:2009: Particle Size Analysis - Laser Diffraction Methods

Deviations:

no

Qualifier:

equivalent or similar to guideline

Guideline:

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

Version / remarks:

adopted May 1981

Qualifier:

equivalent or similar to guideline

Guideline:

other: CIPAC MT 187: Particle Size Analysis by Laser Diffraction

Guideline:

other: ECHA guidance document R.7a

Version / remarks:

Guidance on information requirements and chemical safety assessment,
Chapter R.7a: Endpoint specific guidance, version 6.0, July 2017,
European Chemicals Agency

GLP compliance:

yes (incl. QA statement)

Type of method:

Laser scattering/diffraction

Type of particle tested:

primary particle

Type of distribution:

volumetric distribution

Mass median aerodynamic diameter:

21 µm

Remarks on result:

other: Approximated from laser diffraction results (see details on results).

Remarks:

Standard deviation cannot be given, because two series of measurements (three, each), do result in two final values (continuous measurement). Resulting values are nearly identical (see details on results).

No.:

#1

Size:

<= 5 µm

Distribution:

10 %

Remarks on result:

other: L10

No.:

#2

Size:

<= 21 µm

Distribution:

50 %

Remarks on result:

other: L50

No.:

#3

Size:

<= 49 µm

Distribution:

90 %

Remarks on result:

other: L90

The test item consisted of crystalline particles which appeared irregularly shaped.

The particle size distributions determined in the first and second test series are shown in the attached illustration, respectively. For each test series fractions (left axis of the ordinate) and the siftings (right axis of the ordinate) are presented in percent by volume as a function of the particle size. Median values were calculated from unrounded values.

The median particle size L₅₀ (D (v, 0.5): 50 % of particle volume or particle mass with lower particle diameter) deduced from these distributions were:

1^st test series: L₅₀ = 20.6 µm

2^nd test series: L₅₀ = 20.4 µm

The average of the median particle size L₅₀was:

L₅₀= 21 µm

The particle size L₁₀ (D (v, 0.1): 10 % of particle volume or particle mass with lower particle diameter) deduced from these distributions were:

1^st test series: L₁₀ = 4.5 µm

2^nd test series: L₁₀ = 4.5 µm

The average of the particle size L₁₀was:

L₁₀= 5 µm

The particle size L₉₀ (D (v, 0.9): 90 % of particle volume or particle mass with lower particle diameter) deduced from these distributions were:

1^st test series: L₉₀ = 49.1 µm

2^nd test series: L₉₀ = 48.2 µm

The average of the particle size L₉₀ was:

L₉₀= 49 µm

The maxima of the particle size distribution were observed at approximately 1 µm (small peak) and approximately 25 µm (predominant peak).

The measurement using laser diffraction delivers a volume-weighted mean diameter L50. For spherical, non-porous particles of unit density L50 is the same as the Mass Median Aerodynamic Diameter (MMAD). If the particle density is higher than unity (test item 1.48), the MMAD is higher than L50; in case of non-spherical particles (applies to the test item: irregular shape) the MMAD will generally be smaller than the volume equivalent size reported by laser diffraction (L50). If the test item consists of a homogeneous material, with a constant density, the volume based distribution equals to the mass based distribution. This most probably applies to the test item (crystalline particles). According to Boer (thesis, 2005), "... density and shape factor (both being > 1) normally widely compensate each other." This applies to densities >1 between 1.2 to 1.5 g/cm^3 (test item: 1.48) and shapes differing from spheres (e.g. cylinder with l/d =4). Accordingly, for the test item MMAD will be approximately equal to L50.

Boer, A. H. D. (2005). Optimisation of dry powder inhalation: The application of air classifier and laser diffraction technology for the generation and characterisation of aerosols from adhesive mixtures. [Groningen]: [S.n.].

Conclusions:

Particle size distribution of the test item (laser diffraction; ISO 13320 & CIPAC MT 187):
median particle size L50 = 21 µm; L10 = 5 µm; L90 = 49 µm

Executive summary:

A reliable and valid study on particle size distribution of the test item using laser diffraction was performed compliant with GLP under consideration of the following guidelines:

CIPAC MT 187: Particle Size Analysis by Laser Diffraction;

ISO13320:2009: Particle Size Analysis - Laser Diffraction Methods;

OECD Test Guideline 110: Particle Size Distribution;

Guidance on information requirements and chemical safety assessment, Chapter R.7a: Endpoint specific guidance, version 6.0, July 2017, European Chemicals Agency.

The test item consisted of crystalline particles which appeared irregularly shaped. Malvern Master-Sizer 2000 was used with sample dispersion unit Scirocco 2000.

The mathematical model applied was Fraunhofer-diffraction for opaque and spherical particles.

The control software automatically performed three measurements. The average of these three measurements was given as result. Two test series of three measurements each were performed. The measurement time was 8 s.

Replicate measurements were identical or very close to each other. The following final results were obtained from these particle size distributions:

Average (n=2) median particle size L50 (D (v, 0.5) (50 % of particle volume or particle mass with lower particle diameter):

L50 = 21 µm

Average (n=2) particle size L10 (D (v, 0.1) (10 % of particle volume or particle mass with lower particle diameter):

L10 = 5 µm

Average (n=2) particle size L90 (D (v, 0.9) (90 % of particle volume or particle mass with lower particle diameter):

L90 = 49 µm.

Based on the specific properties of the test item, the L50 as determined from laser diffraction will approximately equal the MMAD.

Description of key information

Particle size distribution of the test item (laser diffraction; ISO 13320 & CIPAC MT 187):

Median particle size L50 = 21 µm;

L10 = 5 µm;

L90 = 49 µm

Based on the specific properties of the test item, the L50 as determined from laser diffraction will approximately equal the MMAD.

Additional information

A reliable and valid study on particle size distribution of the test item using laser diffraction was performed compliant with GLP under consideration of the following guidelines:

CIPAC MT 187: Particle Size Analysis by Laser Diffraction;

ISO13320:2009: Particle Size Analysis - Laser Diffraction Methods;

OECD Test Guideline 110: Particle Size Distribution;

Guidance on information requirements and chemical safety assessment, Chapter R.7a: Endpoint specific guidance, version 6.0, July 2017, European Chemicals Agency.

The test item consisted of crystalline particles which appeared irregularly shaped. Malvern Master-Sizer 2000 was used with sample dispersion unit Scirocco 2000.

The mathematical model applied was Fraunhofer-diffraction for opaque and spherical particles.

The control software automatically performed three measurements. The average of these three measurements was given as result. Two test series of three measurements each were performed. The measurement time was 8 s.

Replicate measurements were identical or very close to each other. The following final results were obtained from these particle size distributions:

Average (n=2) median particle size L50 (D (v, 0.5) (50 % of particle volume or particle mass with lower particle diameter):

L50 = 21 µm

Average (n=2) particle size L10 (D (v, 0.1) (10 % of particle volume or particle mass with lower particle diameter):

L10 = 5 µm

Average (n=2) particle size L90 (D (v, 0.9) (90 % of particle volume or particle mass with lower particle diameter):

L90 = 49 µm.

Based on the specific properties of the test item, the L50 as determined from laser diffraction will approximately equal the MMAD.