Particle Size Analysis

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Particle Size Analysis

• Kausar Ahmad
• Kulliyyah of Pharmacy

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Contents

• Types of methods
• Factors influencing selection of methods

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Need to analyseacademic

• basic facts to understand the phenomena
• molecules become particles
• particles become granules
• granules become tablets, extrudates,
  microcapsules, etc

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Need to analyseprocess

• At least twenty operations are carried out on
  divided solids
• crystallization to formulation
• formation of particles
• drying
• granulation
• mixing compression
• dissolution
• Specific operations dehydration/impregnation,
  spherical crystallization and the series of
  operations involved in micro-encapsulation.

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Particle-related advances

• use of cholesteric liquid crystals and custom
  microencapsulation technologies in the personal
  care industry www.hallcrest.com/about
• microencapsulation technology to deliver omega-3
  oils and other ingredients into functional
  foods.... www.ocean-nutrition.com/inside.asp?cmPa
  geID

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Size range
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Interactions between materials and processes

• Influenced by particle size
• Need to choose
• correct scale of observation e.g.right sizing
  method
• appropriate parameters e.g. right aperture,
  lens, medium
• right measurements e.g. calibrated, good quality
  standards
• to prepare the right material for the expected
  function

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Example

• After size reduction, lots of fines were
  generated because of bad process condition.
• To separate fines from product, a series of
  cyclones were used.
• Eventually, the fines must be trapped using a
  dust filter.
• WHAT IS THE SPECIFICATION of the filter cloth?

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How to determine spec of cloth?

• Filter cloth is used to trap dust
• Pore size of cloth must be smaller than dust
• Hence, must know size of fines!!
• To effectively control the processes IN
  manufacturing, size of raw materials, in-process
  materials and finished goods must be established.

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Size distribution of products fines

• How to detect the size of a sample that contains
• Products? . ?normal distribution
• fines?....................................?normal
  distribution
• Products and fines?..............?SKEWED
• What method to choose?
• Can sieving be used? Must consider screen size.
• Coulter counter? Size range for a particular
  aperture?
• Microscopy? Magnification? Limitation?

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Sample with wide size distribution

• Not desirable as a product
• Rate of dissolution differs
• Processing problem
• Fines tend to agglomerate
• Fines may affect flow
• Measurements must be carried out more than once
• Coulter counter - at least two apertures
• Exercise how about laser diffraction?

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What to analyse?

• Powders
• Granules
• Liquids
• Emulsions
• Creams
• Suspensions/dispersions

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If powder? Consider

• Flowability/dispersibility
• Poor if too fine. Why?
• Exercise how to counter this problem when using
  Coulter?
• Shape
• Crystalline geometric shape
• Acicular needle-shape
• Fibrous thread-like
• Granular equidimensional irregular shape
• Spherical

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If emulsions? Consider

• Will the size change upon dilution?
• Can you use Coulter principle to measure size of
  fine sugar?
• Will there be changes in zeta potential that may
  affect stability?
• Can the technique employed analyse neat sample?

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Dimensions

• Diameter
• Most of the time not actual diameter BUT
  equivalent diameter
• Mean
• Mode
• Size distribution
• Normal
• Skewed
• Polydispersity
• Particle shape
• Statistics

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Availability and cost

• Cheap
• Sieves
• Moderate
• Light microscopy
• Coulter counter
• Laser diffraction
• Sedimentation

• Expensive
• Electron microscopy
• Light scattering
• Laser microscopy

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Sieves

• Powder
• Slurry
• Dispersion
• Right sieves with appropriate size interval

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Laser diffraction

• Powder
• Diluted liquid
• Concentrated liquid?
• Right lens and parameters e.g. density

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Microscopy

• Almost all types of samples
• Depends on type of microscopy
• Depends on magnification
• Sample preparation is important

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Light microscope example 1
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Light microscope example 2
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Light microscope example 3
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Light microscope example 4
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Light microscope example 5
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Selecting instrument

• Need to consider
• allowable range of sizes and
• width
• shape
• of the particle size distribution of sample

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Sizing technique for sulfur?
Hint How many types of sulfur preparation
available?
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Sizing technique for red palm oil emulsion?

• Why red palm oil?
• Nutritional values
• Carotene
• Tocotrienol
• National product
• Relatively cheap
• Type of preparation?
• Size range?

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References

• http//www.swri.org/3pubs/brochure/d01/microen/mic
  roen.htm
• Journal of Controlled Release