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Particle size distribution (Granulometry)

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Reference
Endpoint:
particle size distribution (granulometry)
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Start date of the experimental work: 1 February 2018 and completion date of the experimental work: 8 May 2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Version / remarks:
Manual sieve analysis and laser diffraction analysis
Deviations:
not applicable
Principles of method if other than guideline:
To characterise the particle size distribution of the powder. The analysis is conducted initially using a visual microscope and is then undertaken more formally using a Laser Diffraction Particle Size Analyser. The benefit of this procedure is that it allows the operator to obtain a better understanding of the particle characterisation of the material. This includes, but is not limited to, sample clusters and agglomerations which may provide false values in the formal particle size analysis. In these situations, where the operator can assess how easily these clusters or agglomerations are dispersed, ultrasonics may be employed. Owing to the extremely small quantities of material used in this analysis it should be noted that discrepancies can arise between the lower and upper limits of the particle size and the actual value obtained in the formal particle size analysis.
The sample is observed under 3 conditions:
- Direct observation
- Under a microscope using 3.2 objective lens
- Under a microscope using 40 objective lens
GLP compliance:
yes (incl. QA statement)
Type of method:
other: manual sieveing analysis and laser diffraction analysis
Type of particle tested:
other: powder
Key result
Percentile:
other: 10%
Mean:
< 44.9 µm
Remarks on result:
other: Particle Size Analysis using small volume (wet) module (SVM) with Silicone Oil as the dispersant
Key result
Percentile:
other: 50%
Mean:
< 195 µm
Remarks on result:
other: Particle Size Analysis using small volume (wet) module (SVM) with Silicone Oil as the dispersant
Key result
Percentile:
other: 90 %
Mean:
< 691 µm
Remarks on result:
other: Particle Size Analysis using small volume (wet) module (SVM) with Silicone Oil as the dispersant
Key result
Percentile:
other: 0.25 %
Mean:
< 10 µm
Remarks on result:
other: by volume of sample was seen to be < 10.00 μm is 0.25%
Percentile:
other: 88.6% by weight of the sample
Mean:
< 2 000 µm
Remarks on result:
other: Manual sieve analysis

Manual sieve Analysis:

Results: 88.6% by weight < 2000 μm

Full test results:

 Sieve size (μm)  Sieve weight (g)  Sieve + powder weight (g)  Powder weight (g)  % by weight
 < 2000  325.47  1037.53 712.1   88.6
 > 2000  349.44 441.41   92.0 11.4 
      TOTALS  804.0  100.0

Preliminary Solubility And Dispersability For Particle Size Analysis results

 Solution used Soluble  Comments 
 Silicone oil No  Good dispersability 

Comment

Sample had surface active properties and this limited the choice of dispersants. However the sample was found to be well dispersed in silicone oil. Thus silicone oil was investigated and applied for the analysis.

Solubility And Dispersability Test For Particle Size Analysis

Dispersant used: Silicone Oil

         Series 1        Series 2
 Time elapsed 1 (1.5 mg)   2 (1.5 mg)  3 (1.5 mg) 1 (5.0 mg)   2 (5.0 mg) 3 (5.0 mg) 
 10 seconds  Well dispersed        Well dispersed
 30 minutes Well dispersed Well dispersed       
 60 minutes    Well dispersed      Well dispersed       
 90 minutes  Well dispersed        Well dispersed       
 120 minutes Well dispersed        Well dispersed       

Comments : The sample proved to be insoluble, and well dispersed in silicone oil. Silicone oil was therefore used as the dispersant.

LASER DIFFRACTION PARTICLE SIZE ANALYSIS RESULTS:

   Run 1 Run 2   Run 3  Run 4 Run 5  Average ** 
 Volume weighted mean  312 284  306  336  314  106 
 Median  199 192  188  202  197  195 
 Mode  327 336  304  327  328  324 
 d10 - 10 % of material is <  45.2 44.6  44.3  45.3  44.9 44.9
 d50 - 50 % of material is <  199 192  188  202  197  195 
 d90 - 90 % of material is <  701 630  680  756  701  691 

All results are in μm

* Mass median aerodynamic diameter

** Average result is calculated from the entirety of data captured in each run and is not a simple arithmetic mean.

0.25 % by volume of sample was seen to be < 10.00 μm.

Standard deviation results

 Run N° STDVP  % STDVP 
 d10 - 10 % of material is <  45.2 44.6  44.3  45.3  44.9  0.406  0.905 
 d50 - 50 % of material is <  199 192  188  202  197  5.52  2.82 
 d90 - 90 % of material is <  701 630  680  756  701  45.1  6.51 
 GSD  2.894 2.787  2.892  2.981  2.903  0.062  2.1 

GSD = Geometric standard deviation of the lognormal particle size distribution (calculated from d50/d15.78)

STDVP = standard deviation of the population

% STDVP = percentage standard deviation of the population

Coefficient of variation for d50 is less than 3%; d10 is less than 5%. Thus repeatability of the characteristic particles in the size distribution are within the acceptable limits as per the ISO 13320-1 test standard. See comments below regarding coefficient of variation for d90.

Comment

Although the largest particles observed under microscopic investigation were < 500 μm, the sample was sieved to remove lumps/ agglomerations of size > 2000 μm prior to the distribution analysis. It was extremely difficult to breakdown the clumps into individual particles before or during the distribution analysis.

From the standard deviation calculations, d10 and d50 are within the acceptable limits set by the ISO 13320-1 protocol but the d90 was out.

This may be attributed to the inability to breakdown the lumps into individual particles using the apparatus impeller.

Conclusions:
Particle Size Analysis using small volume (wet) module (SVM) with Silicone Oil as the dispersant.
Volume weighted mean 310 μm
Median (d.50) 195 μm
Mode 324 μm
10 % of material is < 44.9 μm
50 % of material is < 195 μm
90 % of material is < 691 μm
by volume of sample was seen to be < 10.00 μm
0.25% Manual sieve analysis indicated that 88.6 % by weight of the sample had a particle size of < 2000 μm. A subsequent laser diffraction analysis on the < 2000 μm sample produced the results above.

Description of key information

Particle Size Analysis using small volume (wet) module (SVM) with Silicone Oil as the dispersant.

Volume weighted mean 310 μm

Median (d.50) 195 μm

Mode 324  μm

10 % of material is < 44.9 μm

50 % of material is < 195 μm

90 % of material is < 691 μm

by volume of sample was seen to be < 10.00 μm

0.25% Manual sieve analysis indicated that 88.6 % by weight of the sample had a particle size of < 2000 μm. A subsequent laser diffraction analysis on the < 2000 μm sample produced the results above.

Additional information