TITLE
Part B: Particle size and
shape analysis with microscope
OBJECTIVES
The objective of this experiment are:
1.
To analyse and
determine the shape and size of particles in various type of samples under
microscope
2.
To observe and compare the size of particles of different samples.
DATE
OF EXPERIMENT
16th November 2015
INTRODUCTION
Particle is construed as
small object of any size from macroscopic scale (10-3 m) to the
atomic scale (10-10 m). Dimension (equivalent diameter of the
particles) of particulates are important in achieving optimum production of
efficacious medicine. Particle size analysis is the integral component of the
effort to formulate and manufacture many pharmaceutical dosage forms. The
analysis of particle size and shape is very important in pharmaceutical science
field because the size and shape of particles will affects the bulk properties,
product performance, processability, stability and appearance of the end
product and eventually affects the absorption of active ingredients of drugs in
the target tissues for treatment of diseases and thus alters the efficacy of
drugs. It is hard and impractical to determine the fine particles more than a
single dimension because fine particle have irregular and different number of
faces, thus, solid particles are often considered as a sphere and the particles
size can be characterized by determination of their diameter.
There are many particle size analysis methods such as
sieve method, microscope method, coulter counter, laser light scattering
method, dynamic light scattering method and so on. The particle size analysis
methods can be categorised into different categories based on several different
criteria such as size range of analysis, wet or dry methods, manual or
automatic methods and speed of analysis.
In
this experiment, microscope method is used to analyse the particle shape and
size of different type of sample. Microscope method is an excellent technique
enable to students or researchers to look at the particles directly. Under the
microscope, shape and size of particles are no doubt can be seen clearly, but
also the good or poor dispersion of particles, and presence of agglomeration
can be determined. This is relatively cheap and it has it disadvantages such as
not suitable for quality control due to skills in handling the samples and
microscope as well as rapid operator fatigue or operator variability on the
same sample. There are three types of microscope can be used in determining the
shape and size of particles which are light microscope, transmission electron
microscope (TEM) and scanning electron microscope (SEM). Scanning electron microscopy is used
when a three-dimensional particles is required. Generally, in using microscope
method, the equivalent diameters of particles of different samples are
determined for particle size analysis. There are three ways in measuring
equivalent diameters, which are projected area diameter, da,
projected perimeter diameter, dp and Feret’s and Martin’s diameter.
Most
powders contain particles with large number of different equivalent diameters.
Particle size distribution can be broken down into different size ranges which
can be presented in the form of histogram plotted from data obtained to define
the size distribution and compare the characteristics of two or more powders
consisting of particles with many different diameters. Histogram is useful in
interpreting the particle size distribution, determination of the percentage of
particles of equivalent diameters and comparing the different particle size
distribution. The distribution plotted in histogram can be divided into three
types which are normal distribution, skewness distribution and bimodal
frequency distribution.
LISTS OF CHEMICALS
Five different type of
sands with various size, 800 mic, 500 mic, 355 mic and 150 mic respectively,
lactose powder and MCC powder
LISTS OF APPARATUS
Microscope, newspaper
PROCEDURE
1. Five different type of sands with
various size, 800 mic, 500 mic, 355 mic and 150 mic respectively, lactose
powder and MCC powder were prepared in
little amount in different plates
2. The various size sand was then put in
very little amount on the slides under microscope to observe and analyze its
particle size and shape with magnification of 10x.
3. The particles observed microscopically
was then sketched and the general shape of the sand particle was determined.
4. Step 2 and step 3 were repeated by
replacing various size sand with sands with 800 mic, 500 mic, 355 mic, 150 mic,
lactos powder, and MCC powder respectively.
1.
Explain in brief the various statistical
methods that you can use to measure the diameter of a particle.
Among the statistical methods that can be used to measure
the diameter of a particle are projected area diameter, projected perimeter
diameter, Feret’s diameter and Martin’s diameter.
Projected area diameter is the diameter of a circle having
the same area as the particle viewed normally to the plane surface on which the
particle is at rest in a stable position. Projected perimeter diameter is the
diameter of a circle having the same circumference as the perimeter of the
particle. These methods are independent of particle orientation as they take
account of 2 dimensions of the particle only. Thus they are less accurate for
asymmetrical particle.
Feret’s diameter is the mean distance between 2 tangents on
opposite sides of the particle. Martin’s diameter is the mean chord length of
projected particle perimeter. These 2 methods take account of both the
orientation and the shape of a particle.
2. State the best statistical method for
each of the samples that you have analysed.
The best statistical method to be used are Feret’s
diameter and Martin’s diameter. This is because both methods provide the
average diameter on many different orientations of the particle to give a mean
value for the diameter of each particle. Therefore, it gives a more accurate
value of average diameter as compared to projected area diameter which does not
take account of the orientation of the particle.
DISCUSSION
In this experiment, the
characteristic of different particles were observed and studied including the
size and the shape using a light microscope. Among the particles observed are
sands with different size of 150 micron, 350 micron, 500 micron, 850 micron and
various size, lactose and microcrystalline cellulose (MCC). Microscopy method
is a technique used to characterize particle size, shape and volume
distribution through the direct visualisation and measurements of small
particles. Light microscope works according to the principle of passing the
visible light transmitted or reflected from a sample through single or multiple
lens to allow the magnification of the sample. In this experiment, 10x10
magnification is used throughout the experiment.
Through this experiment, it
is found that the shapes and sizes of different particles are distinct from
each other. All sand particles have irregular shapes as some of them have
pointed edges and the size of sand particles increases in order of 150 micron,
350 micron, 500 micron and 850 micron. Sand particles of various size have
different sizes of particles in it. As for MCC and lactose, both of these
particles have a granular shape without any pointed edges like those in sand
particles and their sizes are much smaller than the 150 micron sand particles.
The difference between MCC and lactose is that MCC particles are acicular while
lactose particles are fine rounded. The particles are dispersed evenly on the
slide before observing to prevent the particles from sticking together and thus
avoid agglomeration. During the observation of the particles, the shape and
size of the particles are actually analysed in a two-dimensional image. Similar
particles may appear to be different because they may have different
orientation. However, it is assume that the particles are randomly oriented and
viewed in their most stable orientation.
There are 4 main methods to
analyse particle size, which are projected area diameter, projected perimeter
diameter, Feret’s diameter and Martin’s diameter. Projected area diameter is
the diameter of a circle having the same area as the particle viewed normally
to the plane surface on which the particle is at rest in a stable position. Projected
perimeter diameter is the diameter of a circle having the same circumference as
the perimeter of the particle. These 2 methods are independent of particle
orientation. Feret’s diameter is the mean distance between 2 parallel tangents
on opposite sides of the particle. Martin’s diameter is the mean chord length
of of a particle which divides the projected area. These 2 methods take account
of both the orientation and the shape of a particle.
Precaution steps that were
taken in this experiment includes the careful handling of the particles by
using different spatulas for different particles to avoid mixing of particles.
Besides, the experiment is carried out in a stale air condition to prevent the
particles from dispersing everywhere. Goggles and mask were also worn to
prevent the particles from entering our body.
CONCLUSION
Different particles have
different shapes and sizes. Microscopy is one of the methods to study particle
shape and size through the direct observation of the particles. Diameter of a
particle and be measured through projected area diameter, Feret’s diameter and
Martin’s diameter. The characteristics of particles which includes the shape
and the size is necessary to be understood to increase the efficacy of drugs
through the formulation of drugs in the field of pharmaceutical industry.
REFERENCES
Florence, A. T. &
Attwood, D. 2006. Physicochemical
Principles of Pharmacy. Edisi ke-5. London: Pharmaceutical Press.
Martin, A. 2011. Physcial
Pharmacy: Physical Chemistry Principles in Pharmaceutical Sciences. Edisi
ke-6. Philadelphia: Lippincott Williams & Wilkins.
Cairns,
D. 2008. Essentials of Pharmaceutical
Chemistry. Edisi ke-3. United States of America: Pharmaceutical Press.
Chang, R. & Goldsby, K.
A. 2014. Chemistry. Edisi ke-11. New York: McGraw- Hill Education.
ReplyDeleteHigh-Throughput Screening