Objective
- To analyse the particle shape and size
under the microscope.
- To describe the distribution particle
size and shape.
Date of Experiment
19 November 2015
Introduction
The dimension of the particulate solids are
very important in order to achieve optimum production of efficacious medicines
.The particle size of drugs is determined when the drug is synthesized and
formulated .In the case ,particle size will influence the subsequent physical
performance of medicines and pharmacological of the drugs There are many
methods for the analysis of particle size and shape .In this case , analysis
using microscope is one of the effective ways to determine the particle size
and shape .It is an excellent technique because we can look at the particle
directly and is relatively cheap .One of the disadvantages of using microscope
for analysis the shape and size of particle is the elaborate sample preparation
is slow . Moreover, it is not suitable for quality control.
Apparatus
Microscope, weighing boat
Materials
sand with particle size of (150 mic, 355
mic, 500 mic, 850mic), lactose, sand with various sizes and MCC.
Procedure
1.
Sands with sizes of (150 mic, 355 mic, 500 mic, 850mic), sand with
various sizes, lactose and MCC are placed in the different weighing boat by
using spatula. The weighing boat were labeled according to the content.
2.
The microscope was set up and
ready to be use.
3.
150 mic sand scattered on the
glass slide and covered with the cover slip.
4.
The sand was observed under
the microscope using 4x10 magnification.
5.
The particles were observed
microscopically and the shape was determined.
6.
Steps 3 to 5 were repeated by
using (355 mic, 500 mic, 850mic), lactose ,sand
with various sizes and MCC.
Results
Question
1.Explain
in brief the various statistical method that u can use to measure the diameter
of a particle.
The first method is the Feret’s
diameter.The Feret diameter or Feret's 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. Therefore ,it
is also called the caliper diameter,
referring to the measurement of the object size with a caliper. This measure is
used in the analysis of particle sizes, for example in microscopy,
where it is applied to projections
of a three-dimensional (3D) object on a 2D plane. In such cases, the Feret
diameter is defined as the distance between two parallel tangential lines rather than planes.
Moreover ,Martin diameter can be one of the method to determine the
diameter of a particle .It is a specific
method for measuring the diameter of irregular shaped particles, 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 essence, Martin’s diameter measures the chord of a particle and is useful
for estimating the surface area of an irregular non-spherical particle.
Besides ,projected area
can be one of the methods to measure the diameter of a particle .The projected area diameter is the diameter
of a sphere having the same projected area as the particle. Projected area is two-dimensional area measurement of
a three-dimensional object by projecting its shape on to an arbitrary plane.
Besides, another useful method is the projected perimeter diameter which is
based on the circle having the same perimeter as the particle. Both of these
methods are independent upon particle orientation. They only take into account
of 2 dimensions of the particle, thus inaccurate for unsymmetrical particle.
Lastly ,we can use
Fourier analysis to determine the diameter of a particle. It provides an
accurate quantification of particle morphology and texture. They describe the
overall shape of soil particles which is known as morphology . A summary of
higher order descriptors provides textural information which is related to
local roughness features which is defined as texture.
2.State
the best statistical method for each of the samples that you have analysed.
Martin's diameter and Feret's
diameter of a particle depend on the particle orientation under which the
measurement is made. Thus, obtaining a statistically significant measurement
for these diameters requires a large number of randomly sampled particles which
are measured in an arbitrarily fixed orientation. Since Martin's diameter,
Feret's diameter, and projected area diameter are based on the two-dimensional
image of the particles, they are generally used in optical and electron
microscopy.
Nowadays, pharmaceutical manufacture of products quality is more
dependent on the particle size control as this is becoming increasingly
apparent in the pharmaceutical industry. Precise particle size control
technologies have also assisted in the development of drug delivery platforms
for the delivery of a medicament to various part of the body.
In order to determine the particle size, several methods can be used
such as microscopy, sieving, sedimentation techniques and etc. Besides, we can
further analyze the particle size by using Feret’s diameter or Martin’s
diameter. Martin’s diameter refers to the length of the line which bisects the
particle image, while Feret’s diameter refers to the distance between two
tangents on opposite sides of the particle, parallel to some fixed direction.
This is because the Feret’s and Martin’s diameter is the best
statistical method in which
both of them use statistical diameter which are the average over many different
orientations to produce a mean value for each particle diameter.because both of them use statistical
diameter which are the average over many different orientations to produce a
mean value for each particle diameter.These two methods consider the
orientation of particles, hence this increase the accuracy of the results
obtained.
Microscope is used in this experiment to examine the various particle
size and shapes of sands and powder because the microscope magnification are
sufficient enough to allow adequate characterization of small particles. Error
can be minimised if magnification and the light is sufficient that the image of
particles produced is sharp and clear. Whereby, we can examine each particle
individually by observing the 2D shape, colour, etc. However, we have to know
that we unable to obtain a 3-Dimensional orientation of particle size and shape
through a microscope.
In this experiment, we had analyze 5 different types of sands and
powders (MCC, lactose, 150 mc, 355 mc, 500 mc, 850 mc, various size ) by using
a microscope. The particles which are observed microscopically were
sketched and the general shape for each particle were determined. We found that the samples that we
observed are varies in term of their shape and size. They can be characterized by the
range of from low sphericity to high sphericity, from very angular, angular,
sub-angular, sub-rounded, rounded and well-rounded. For instance, the size of
850mc sand is larger than 150mc sand as we can compare of the image of sample
we got in which both are irregular shape and asymmetry.
The magnification which we used during this experiment set to be
constant for all 6 sample which is 4x10 magnification. This is important so
that we can compare the size and shape of the particle clearly and easily.
Besides, we have to make sure that the sample particles is well-spread
throughout the slide and dispersed evenly until it is a thin layer before
observing it under a 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.
There were several precaution steps taken
in this experiment such as make
sure that the fan is switched off and the sand granules and powder were carefully
handled so that it will not spread all over the table and to ensure cleanliness of work place. Moreover, we are advised to wear goggles and
mask to prevent the sand and powder gets into our eyes and to protect ourselves
safety.
Conclusion
As from the
observation of the image obtained from microscope by using a fix magnification,
we can conclude that the shape and size of the sands and powder are different.
All particles are varies in their size and have an asymmetrical and irregular
shape.
References
1. Physicochemical
Principals of Pharmacy (2nd Edition) AT Florence and D.Attwood, The Macmillan
Press Ltd.
2. Michael
E.Aulton, 2007, Aulton's Pharmaceutics The Design And Manufacture
Of Medicines, Third Edition, Churchill Livingstone
Elsevier (page 122-134)
3. Pharmaceutics, The science
of dosage form design (2nd Edition) Michael E.Alton Edinburgh London New York
Philadophia St Louis Sydney Toronto 2002.