Title: Particle
size and shape analysis using microscope
Date: 22th November
2016
Objective: To investigate
and analyse the size and general shape of particles of different types of sands and powders under
microscope.
Introduction:
Particle size and shape are
important in achieving optimum production of efficacious medicine. Bioavailability is often directly related to
particle size because it controls solubility characteristics of the drugs.
Dissolution rate is directly proportional to particle surface area. The smaller
the particle size of the drugs, the larger its surface area is. So, a smaller
particle size promotes faster drug dissolution. Particle size distribution is
also relevant as a narrow distribution produces more uniform dissolution.
Formulations with even a small number of relatively large particles may take
some time to dissolve completely, but this may be the design intent. Hence,
analysis of particle size and shape is always important before a medicine reach
the consumer.
In
order to interpret and analyse the particle size and shape of the solid drugs,
a few method can be used. One of the common method that is use is microscopic
analysis.
Apparatus:
Electron microscope
100ml beaker
Spatula
Glass slide
Material:
5 different types of sand
MCC powder
Lactose powder
Procedure:
1)A microscope was set up.
2)Sand with particle size of 150mic, 355mic, 500mic, 850mic and various
sizes , lactose powder and MCC were place in
different beaker with label A, B,C,D,E, lactose and MCC respectively using a
spatula .
3)Sand from beaker A was scattered on a
glass slide.
4)The sand was observed under microscope
using different magnification.
5)General shape of the sand was
determined.
6)Step 3,4 and 5 were repeated using
sand from beaker B,C, D, E, lactose and MCC.
Result:
150mic(25x)
The particles size of the sand is very small,
almost the same in size but different in shape.
355mic(4x)
The sand particles of 355 mic is bigger than that of 150 mic. The
particles are irregular in shape.
500(25x)
The sand particles are
bigger than the sand of 150 mic and 500 mic stated above and similar in size. Their shapes are irregular but are generally of low
sphericity and look angular.
850(25x)
The sand particles is larger than the sand
particles of 150micron, 355micron and 500micron and almost same in size. The
particles shapes are irregular, but generally they are of very low sphericity.
Various size(4x)
The shape of the sand particles is very irregular
and different sizes of sand particles are observed. Some particles appear to
the much bigger than all the 150mic, 355mic, 500mic, and 800mic sands observed
before and some has approximately same size with them.
MCC(4x)
Particles of MCC powders are almost the same size
and shape as most of the particles give rice-shape appearance.
Lactose (4x)
Lactose has the smallest particle size compared to all the samples
above. The particles are of more constant shape as they are generally
spherical. The particles are of almost the same size in the sample.
Discussion
In this experiment, different types of sands and
powders which are lactose powders, MCC powders, 150micron sands, 355micron sands,
500micron sands, 850micron sands and sands of various sizes are examined using
a light microscope. The particle size
and shape are examined and analysed. From the observation, the general shape of
sand particle is not uniform and varies distinctly from one and another. The
shape of MCC and lactose is especially difficult to define due to the very
small size of the powder particle.
From
the observation of sand particle, due to the larger size the sand can be
distributed evenly so each particle shape can be seen and observed clearly. On
the whole, the sand particles are asymmetrical and sizes vary. On the other
hand, the powder are fine, thus are distributed unevenly and single particle is
difficult to obverse. On the whole, the particle are more uniform in shapes and
sizes.
Besides, the particle size analysis can be done further
by using various methods such as projected area diameter, projected perimeter
diameter and better by using Feret’s diameter or Martin’s diameter, as these
two methods consider the orientation of particles and, the particles can be
examined individually. Feret’s diameter is the mean distance between two parallel
tangents to the projected particle perimeter while Martin’s diameter is the
mean chord length of the projected particle perimeter. Besides, electron
microscope can be used to examine the orientation and shape of the image in
three diminsional.
During the experiment, we have to make sure that the sample
particles is well-spread throughout the slide and dispersed evenly under the
microscope. It is to avoid the agglomeration formed and ensure the image of
specimen we obtain is accurate and clear in term of their shape and size. We also
are advised to wear goggles and mask to prevent the sand and powder gets into
our eyes and to protect ourselves safety.
Question
1.
Describe the variety of statistical
method used to measure diameter of particles.
Monosized particles consist of
equivalent spheres with the same diameter. However, most powders contain
particles with different diameters and size. First, projected area diameter is
used to measure the equivalent area to that of projected image of the particle . Projected area is
two-dimensional area measurement of a three-dimensional object by projecting
its shape on to an arbitrary plane. Likewise, projected diameter is also used
by which the circle having the same perimeter as the particle. However, the
weakness is that these method do not take the orientation into consideration.
Only two dimension of particle in
consideration is inaccurate for unsymmetrical particle.
Martin’s diameter is also used to determine the diameter of a
particle. By using this method, the diameter of irregular shaped particles is
measured. Martin’s diameter is the measured distance between opposite sides of
a particle, and is measured transverse to the particle on a line that bisects
the projected area. In other words, Martin’s diameter measures the chord of a
particle and is useful for estimating the surface area of an irregular
non-spherical particle.
Feret’s diameter also called the caliper diameter, is a
measure of an object size along a specified direction. It can be defined
as the distance between the two parallel planes restricting the object
perpendicular to that direction generally. The object size is measured with a caliper. This measure is
used in the analysis of particle sizes and is applied to projections of a three-dimensional (3D) object on a 2D plane.
Thus, it is also defined as the distance between two parallel tangential lines
rather than planes.
Feret’s diameter and Martin’s diameter depend on both the
orientation and the shape of the particle. These are statistical diameters
which are averaged over many different orientations to produce a mean value for
each particle diameter.
2.
The best method that should be used
on this experiment.
Feret’s
and Martin’s diameter will be the best method as these methods are
averaged over many different orientations to produce a mean value for each
particle diameter.
Conclusion
As a conclusion, each of the particles has
different shape and size and they are irregular by using microscope to analyze.
The size of the particle which is smallest is lactose powders, followed by MCC
powders, 150micron sands,
355micron sands, 500micron sands, 850micron sands and sands of various sizes.
Reference
1) Physicochemical Principals of Pharmacy (2nd
Edition) AT Florence and D.Attwood, The Macmillan Press Ltd.
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