PRACTICAL 4 : PART B - MICROSCOPIC SIZE ANALYSIS
TITLE :
Analysis of Particle Size and Shape under Light Microscope
DATE OF EXPERIMENT :
17th of November 2014
OBJECTIVES :


INTRODUCTION:
The size and shape of particle can
be analysed using various method. In this experiment, we used microscope as the
method to achieve our objectives. There are three types of microscope that can
be used to analyse size and shape of the samples which are light microscope,
transmission electron microscope (TEM) and scanning electron microscope (SEM).
We used light microscope which function for the particles or samples to
disperse on a microscope slide to avoid analysis of agglomerated particles. The
analysis using this type of microscope is to determine the diameter, shape, and
surface area of a particle. We are using various kind of sizes of sand, which
are 150 µm, 355 µm, 500 µm, 850 µm, sand with all of this sizes that already
been mixed together, lactose and microcrystalline cellulose (MCC) as samples for this experiment. Some batches
of samples may differ by such a small amount that this difference is lost
during the translation to a circle equivalent or spherical-equivalent
diameter. In this experiment, we observe
different sizes of particles under a microscope, draw and take picture of the
particles’ observed.
MATERIALS:
Sand (150 µm, 355 µm, 500 µm, 850 µm, mixture of various size)LactoseMicrocrystalline cellulose (MCC)
APPARATUS:
Light microscope, Weighing boatEXPERIMENTAL PROCEDURES :
Particle size and shape analysis using microscope
1) 5 different types of sands (150 μm, 355μm, 500μm, 850μm and mixture of various sizes of sand particles) and powders (MCC and lactose) were analyzed with particular emphasis on the size and shape of the particles by using a microscope.
2) The particles observed microscopically were sketched and the general shape for particular material was determined. The magnification used in this experiment was 10x.
RESULTS:
Items to be observed
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Observed under microscope
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Drawing
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1. Mixture of various size of sand particles
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2. Sands (150μm)
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3. Sands (355μm)
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4. Sands
(500μm)
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5. Sands (850μm)
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6. Lactose
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7. Microcrystalline Cellulose ( MCC)
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DISCUSSION :
Particle size is one of
the most important parameters in materials science and technology as well as
many other branches of science and technology, from medicine, pharmacology and
biology to ecology, energy technology and the geosciences. The theoretical backbone
is the statistics of small particles.Except for sieve classification (which has
lost its significance for particle size analysis today, although it remains an
important tool for classification) the most important particle size analysis
methods are treated in some detail, in particular are the sedimentation
methods, laser diffraction, microscopic image analysis dynamic light scattering, electrozone
sensing, optical particle continuing, XRD line profile analysis, adsorption
techniques and mercury intrusion.
If describing a 3D
particle size is complex then quantifying shape is even more complicated. There
are an almost infinite number of ways to describe a complex shape and in doing
so we seem to be deviating from our stated objective of reducing a sample to
one quantifiable number. Measuring size alone is sometimes insufficiently
sensitive to identify important but subtle differences between samples. Some
batches of samples may differ by such a small amount that this difference is
lost during the translation to a circle equivalent or spherical-equivalent
diameter.
Particle size, in the
sense commonly used, is a linear length measure, measured in SI unit [m].In
this sense it can be uniquely defined only for spheres, where it is the
diameter (or radius). For all other shapes, particle size must be clearly
defined via the measuring procedure. So called derived diameters are determined
by measuring a size-dependent property of the particle and relating it to a
single linear dimension. The most widely used of these are the equivalent
diameters, in particular the equivalent spherical diameters. Important
equivalent diameters are volume equivalent sphere diameter, surface equivalent
sphere diameter, hydrodynamic sphere diameter, sieve diameter, laser
diffraction equivalent diameter, projected area diameter and volume surface
diameter.
Other equivalent
diameters which are less frequently used for example the perimeter equivalent
diameter of a particle outline. Apart form the equivalent diameters there are other size measures
which can be used to quantify particle size, mainly in microscopic image
analysis of 2D particle outlines, among them the chord or intercept lengths
(including the Martin diameter, for example the length of the chord dividing
the projected particle area into two equal halves) and the caliper or Feret diameters
(including the maximum and minimum Feret diameter)
Particle shape is a
complex geometric characteristic. It involves the form and habit of the particle
as well as features like convexity and surface roughness. The literature on
shape characterization is enormous and so is the number of possible definitions
of shape factors. Characterizing size and
shape of particles is critical for the development of a drug product since most
pharmaceutical processes such as granulation, mixing and compaction are affected
by these properties. An ideal particle characterization technique should
provide an accurate determination of the volume-weighted particle size
distribution combined with a reliable definition of the particle shape. In
addition, very few techniques directly measure particle shape. The goal was to
use optical microscopy with image analysis to confirm the accuracy of the other
particle size techniques.
Equivalent diameters
from three particle size techniques including laser light scattering (LLS), focused
beam reflectance (FBRM) and dynamic image analysis (DIA) were compared to
optical microscopy with image analysis (OM/IA). Optical microscopy is
considered the most accurate because the size and shape of the individual
particles can be observed and measured .To do this comparison several factors
were considered such as relative size (5μ, 50μ or 500μ) and shape (spherical or
irregular) of the sample, objective and camera resolution sample size spherical
volume calculation and accuracy of the system based on analysis of a standard.
In this experiment,
five different types of sands and powders (MCC and lactose ) with particular
emphasis on size and shape were analyzed using microscope. The particles which
are observed microscopically were sketched and the general shape for each
particle were determined. The general shape observed were spherical and
irregular. The magnification that was used for all the particles that were
observed was ×10. There were five different diameters for the sands which are
namely (150 mic, 355 mic, 500 mic, 850 mic and various). Based on the
observation, the sizes of all particles differs from each other. The methods
used to determine the particle size analysis are sedimentation, laser
diffraction and also microscopic image analysis. Method used for this
experiment is microscopic image analysis. Type of the particle surface was
namely coarse and fine surface.
There are some
precautionary steps to be taken during experiment in order to obtain accurate
results. Although microscopes may seem sturdy, they are actually quite fragile
as evidenced by their glass lenses and delicate focusing mechanisms. Always
pick up a microscope using both hands, one holding the arm of the microscope
and the other supporting its base. Position the arm of the microscope toward
you and the stage so that flat platform used for holding the specimen is
directed away from you. When using your microscope at its highest
magnification, some models require special preparation of the specimen or lens.
CONCLUSION:
Based on the experiment, microscopic image analysis is one of the method used to determine shape and size of the particles. The general shape of the particles observed from the experiment were spherical and irregular. The size of the particles differ from each other. Surfaces of the particles were namely coarse and fine.
QUESTIONS:
1.
Explain in brief the various statistical methods that you can use to measure
the diameter of the particle.
Diameter of a particle can be measured based
on a circle having the same perimeter as the particle, which known as projected
perimeter diameter. Meanwhile, projected area diameter can be measured from a
circle of equivalent area to that of the projected image of a solid particle.
There are also methods called Feret's
diameter and Martin's diameter. These two methods are dependent on both the
orientation and the shape of the particles. The value of diameter is averaged
over many different orientations produced for each particle. The only difference
between these two is, Feret's diameter refers to the mean distance between two
parallel tangents to the projected diameter. While Martin's diameter refers to
the mean chord length of the projected particle perimeter which can be
considered as the boundary separating the particle equally.
2. State the best statistical method for each sample
used in this experiment.
355 micron sand : Martin's diameter
500 micron sand : Martin's diameter
800 micron sand : Martin's diameter
Vary in Size sand : Martin's diameter
REFERENCES:
- http://www.particlesciences.com/docs/DDT-Particle_Size_Dist-May_09.pdf
- Michael E.Aulton, 2007, Aulton's Pharmaceutics The Design And Manufacture Of Medicines, Third Edition, Churchill Livingstone Elsevier (page 122-134)
- http://www.nature.com/nature/journal/v162/n4113/abs/162329b0.html
- http://www.ncbi.nlm.nih.gov/pubmed/1437996
- 3.http://www.surfaceanalysis.ru/surface/categors/1f/74/content_128015234686.pdf