Particle Size Sizing Technique 2: hydrodynamic chromatography sieving microscopy

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Particle Size Sizing Technique 2 hydrodynamic
chromatography sieving microscopy

• Kausar Ahmad
• Kulliyyah of Pharmacy, IIUM

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Hydrodynamic Chromatography
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HDC instrument (e.g.Polymer Lab)
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HDC Operation
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Results generated by HDC
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LiposomePL-PSDA (Polymer Lab HDC mechanism)
What is the volume average diameter?
What is the polydispersity index?
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Sieving

• POWDER can be separated into various size
  fractions by vibrating sieve loaded with sample
  to enable the particles of size less than that
  of the mesh openings to pass through and the
  over size to remain in the sieve.

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Dry Sieving

• Dry sieving
• is adopted for free flowing powder samples of
  size range varying frome.g. 4mm down to 25µm.

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Sieves

• A standard test sieve is generally made of a
  woven wire mesh cloth
• specified wire thickness with square openings
• Standard sieves are made according to recommended
  norms to maintain opening size interval between
  successive sieves.
• The ratio between successive sieves is kept as a
  constant such as 1.414 and hence the sieve size
  varies in geometric progression.
• fixed to a rectangular or circular frame

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Sieving Procedure

• The sieves are arranged one above the other in
  such a way that the lowest size sieve opening is
  at the bottom and the highest at the top.
• The bottom pan is stacked below the finest sieve.
• Known amount of powder sample is loaded on the
  top sieve and then closed with the lid.
• This arranged sieves set is placed in a
  mechanical sieve shaker and it is operated for a
  definite time (ca. 5 min).
• Then the amount of the material present in each
  sieve is weighed separately and the values are
  tabulated along with their corresponding sieve
  opening.

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Arranging sieves

• Sieves stacked

Maximum size
g
f
e
Wire mesh
d
c
b
a
pan
Minimum size
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Table of Sieve Results
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Interpretation of Sieve Results

• From the cumulative weight, the mean diameter
  can be obtained i.e.
• d(0.5) the diameter at which 50 of the
  samples, based on weight falls below it.

Cumulative weight ()
Weight ()
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Microscopy

• The deer tick, is about the size of a freckle.

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Continue Microscopy

• To fly, moths must be light.
• A close-up of the Cecropia Moth scale shows that
  it is mostly air, adding very little weight to
  the moth.

magnification
scale
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Continue Microscopy

• The shells of radiolarians, single-celled
  animals.

magnification
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Principles of Microscopy

• The microscope is an instrument designed to make
  fine details visible.
• The Concept of Magnification
• The image of an object can be magnified when
  viewed through a simple lens.
• By combining a number of lenses in the correct
  manner, a microscope can be produced that will
  yield very high magnification values.
• Lenses and Optics
• The action of a simple lens, similar to many of
  those used in the microscope, is governed by the
  principles of refraction and reflection .

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Using light microscopy to determine size
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Scanning Electron Microscope

• Conventional light microscopes use a series of
  glass lenses to bend light waves and create a
  magnified image.
• The Scanning Electron Microscope creates the
  magnified images by using electrons instead of
  light waves.
• The SEM shows very detailed 3-dimensional images
  at much higher magnifications than is possible
  with a light microscope.
• The images created without light waves are
  rendered black and white.

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SEM Technique

• Samples have to be prepared carefully to
  withstand the vacuum inside the microscope.

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Continue SEM Technique

• Specimens are dried in a special way that
  prevents them from shriveling.
• Because the SEM illuminates them with electrons,
  they also have to be made to conduct electricity.

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Continue SEM Technique

• How do you make a specimen conductive?
• SEM samples are coated with a very thin layer of
  gold by a machine called a sputter coater.

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Continue SEM Technique

• Now the prepared specimen is ready.

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Continue SEM Technique

• The sample is placed inside the microscope's
  vacuum column through an air-tight door.

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Continue SEM Technique

• After the air is pumped out of the column, an
  electron gun emits a beam of high energy
  electrons.
• This beam travels downward through a series of
  magnetic lenses designed to focus the electrons
  to a very fine spot.

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Continue SEM Technique

• Near the bottom, a set of scanning coils moves
  the focused beam back and forth across the
  specimen, row by row.

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Continue SEM Technique

• As the electron beam hits each spot on the
  sample, secondary electrons are knocked loose
  from its surface.
• A detector counts these electrons and sends the
  signals to an amplifier.

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Continue SEM Technique

• The final image is built up from the number of
  electrons emitted from each spot on the sample.

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Information given by SEM

• pore diameter
• particle size
• shape
• surface condition roughness, texture etc.

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SEM setup
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References

• SL Flegler, JW Heckman, KL Klomparens, Scanning
  and transmission electron microscopy, Oxford, New
  York (1993)
• http//www.mos.org/sln/SEM/index.html
• http//micro.magnet.fsu.edu/primer/lightandcolor/p
  olarizedlighthome.html