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Interpreting Your Laser DiffractionParticle Size Analysis ResultsDecoding the Acronyms and Finding Insights
Ian [email protected]/us/particle
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Outline
The Basics
Define Parameters
Choose Parameters
Interpret Results
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The Workflow
+ +
=
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The Problem
=
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The BasicsParticle Distribution of Particles
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The BasicsParticle Size Particle Size Distribution
4 µm
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The Basics
Which is the most meaningful size?
differentsize definitions
differentresults
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The Basics
Which sizes can be measured?
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The Basics
Laser DiffractionEquivalent Spherical Diameter
Dynamic Light ScatteringHydrodynamic Radius
Image AnalysisLengths, Widths, Equivalent Spherical
Acoustic SpectroscopyEquivalent Spherical Diameter
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The BasicsLaser DiffractionAssumes hard, spherical shape model
q% = amount of each sizeby volume
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The BasicsDynamic Light ScatteringAssumes hard, spherical shape model
Frequency % = amount of each sizeby volume
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The BasicsImage AnalysisMeasures particle projection no shape assumption
UndersizePassingQ3
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The BasicsAcoustic SpectroscopyAssumes hard, spherical shape model
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Poll!
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Conclusions
Understand the dataA little goes a long way!
Know something about the particles in your sample
Particles have multiple dimensions, know which dimension your analyzer measures!
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Outline
The Basics
Define Parameters
Choose Parameters
Interpret Results
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Defining Parameters
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Terms, Terms, and more Terms
Particle SizeMonomodal: One PeakBimodal: Two PeaksMultimodal: Multiple Peaks
Monodisperse: All particles have same sizePolydisperse: Particles have many sizes
Volume diameter: Diameter of a sphere having the same volume as the particle
Surface diameter: Diameter of a sphere having the same surface as the particle
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Terms, Terms, and more Terms
Particle SizeFrequency% / q% / Amount of each size by volumep3 / Retained / Sph Vol%
Volume-based diameter Calculated from vol. distribution emphasizes coarse particles (larger volume)
Number-based diameter Calculated from number dist. (individual particles) emphasizes fine particles
Cumulative% on diameter % of distribution finer/coarser than specified size
Diameter on cumulative% Size at which a specified % of distribution is finer/coarser
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Terms, Terms, and more Terms
Particle ShapeAcicular: Needle-shaped, rigidAngular: Edgy, hard anglesFibrous: Thread-like, non-rigidGranular/Blocky: Irregular-shaped, low aspect-ratioSpherical: Regular-shaped, unity aspect ratio
Aspect ratio: Breadth / length OR Length / breadthSphericity: How spherical is the particle?Roundness: How round is the particle?
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Poll!
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Size Terminology
The most common designation is micrometers ormicrons. When very small, in colloid region, measured in nanometers, typically by ultra microscopes or by dynamic light scattering.
10-10 10-810-9 10-610-7 10-410-5 10-210-3 10-1 10-0
meternanometer
Angstrom(Å)
micrometer millimeterMicron or µm mnm mm
0.1µm 1.0µm 10µm 100µm
100 nm
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Visible Particles: Lint, Dust, width of the ridges of fingertips.
Human Hair
Proteins, Viruses, and Macro-Molecules
Emulsions and ColloidsSuspensions and fine powdersSuspensions and fine powdersDust and free flowing powders
Relative Size
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Poll!
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Central Values
Mean Medianand Mode
Size
MeanWeighted AverageCenter of Gravity
Median50% Point
ModePeak of the distributionMost common value
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Three spheres of diameters 1,2,3 units
What is the average size of these spheres?Average size = (1+2+3) ÷ 3 =2.00
This is called the D[1,0] - the number mean
12 3
What does “Mean” mean?
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None of the answersare wrong they have just been calculated using different techniques
X Dnl
[ , ] .1 01 2 3
32 00
X Dns
[ , ] .2 01 4 9
3216
X Dnv
[ , ] .3 01 8 27
32 293
X Dsv
[ , ] .3 21 8 271 2 3
2 57
X Dvm
[ , ] .4 31 16 811 8 27
2 72
Many possible Mean values
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D[4,3] which is often referred to as the Volume Mean Diameter [ VMD ]
D [4,3] =
i i
i i
D nD n
4
3
Monitoring the D[4,3] value in your specification will emphasize the detection of large particles
Volume-based Mean diameter
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Mode
Median
Mean
D[4,3]
Size
Remember: D[4,3] is sensitive to large particles
Central Values revisited
MeanWeighted AverageCenter of Gravity
Median50% Point
ModePeak of the distributionMost common value
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D(v,0.9)D(v,0.1)
Size µmD(4,3) sensitive to large particles
D(v,0.5)median
D(v,1.0)Never use the D100!
10% of the particles are smaller than this diameter
90% of the particles are smaller than this diameter
half are larger than this diameterhalf are smaller than this diameter
Most Common Statistics
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Standard Deviation
Normal (Gaussian) Distribution Curve
= distribution mean = standard deviation Exp = base of natural
logarithms
1 2Y = Exp [ - (x - )2
22 ]
Mean
+1 STD DEV-1 STD DEV
+2 STD DEV-2 STD DEV
68.27%
95.45%
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Distribution Width
Polydispersity Index (PI, PDI)
Span Geometric Std. Dev. Variance Etc…
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Poll!
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Conclusions
Be familiar with the nomenclature
Many parameters can describe distributionD50, D10, D90 commonly usedSee Technical Note 156 in Download Center for more info
Which Mean do you mean?
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Outline
The Basics
Define Parameters
Choose Parameters
Interpret Results
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Choosing Parameters
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Choosing good statistics
Statistics describing the distribution must…Tell us about our processBe relevantBe controlled wellBe reproducible!
Poor precision is the result of either a poor method or poor statistical choices
We can help! [email protected]
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Reproducibility!Prepare, measure, empty, repeat
What would be good reproducibility?Look at the accepted standards
ISO 13320COV < 3% at Median (D50) COV = 100 * (StDev / Mean)COV < 5% at D10 and D90
USP <429>COV < 10% at Median (D50)COV < 15% at D10 and D90
Note: All limits double when D50 < 10 µmNote: Must acquire at least 3 measurements from unique samplings
The Basis for Reliable Data
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Unique, automatic feature in LA-950 softwareSee Technical Note 169 in Download Center
for instructions to use these features
Calculation Automation
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Distribution Extremes
At a distance of a few standard deviations, non-instrumental errors can dominate
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2 and 3 Standard Deviations
95% of the distribution is within 2 standard deviations from the Mean99.7% of the distribution is within 3
standard deviations from the mean
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Reproducibility at the Extremes
If we want the same level of reproducibility at the D99 value as the D50, we need to analyze similar amounts of material in the D99 histogram band
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Better Method to Monitor Extremes
Instead of specifying the D95, D99, D99.99, D100, DMax
Specify the % of material greater than a certain size
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Poll!
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Conclusions
Parameters should reflect product performanceBut don’t make your life more difficult than it needs to be! See Webinar TR007 Setting Size Specifications and Technical Note 161 for more information
Look to appropriate standardsISO 13320, USP <429> can provide guidance
Avoid monitoring the extremes whenever possibleBetter to use D(4,3) when you want spec. to be sensitive to presence of large particles
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Outline
The Basics
Define Parameters
Choose Parameters
Interpret Results
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Advanced Result Interpretation
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GeneralMultiple ModesMultiple peaks can be better described individually
D50 D90D10
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Laser DiffractionMultiple ScatteringWatch for finer “particles” appearing with increasing concentration
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Multiple Scattering Example Zoom
0.00E+00
1.00E-01
2.00E-01
3.00E-01
4.00E-01
5.00E-01
6.00E-01
65 70 75
Detector Number (higher detector numbers for smaller particles)
Ligh
t Int
ensi
ty
1 Bottle2 Bottles3 Bottles4 Bottles5 Bottles6 Bottles7 Bottles8 Bottles9 Bottles10 Bottles
Multiple Scattering Example
0.00E+00
5.00E-01
1.00E+00
1.50E+00
2.00E+00
2.50E+00
45 50 55 60 65 70 75
Detector Number (higher detector numbers for smaller particles)
Ligh
t Int
ensi
ty
1 Bottle2 Bottles3 Bottles4 Bottles5 Bottles6 Bottles7 Bottles8 Bottles9 Bottles10 Bottles
Multiple Scattering
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1 bar
2 bar
3 bar
Laser DiffractionDispersing AgglomeratesWatch for no change in coarsest particles with changing energy
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High = 3 barMid = 2 barLow = 1 bar
Laser DiffractionBreaking ParticlesWatch for finer particles being created with increasing energy
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Conclusions
Look at the distribution graphSee the forest AND the trees
Precision != AccuracyVary measurement and calculation parameters
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For More Details
Visit www.horiba.com/us/particle
Contact us directly at [email protected]
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