Title:
Particle Size And Shape
Analysis Using Microscope
Date
of Experiment:
20 November 2014
Objective:
To investigate and analyse the
size and general shape of particles of different types of sands and powders
under light microscope.
Introduction:
The ability to analyze and characterize particle size
and shape can significantly improve the manufacturing efficiency and product
performance. Thus, the use of microscopy and image
analysis is the most reliable technique to
characterize particle shape, size and volume distribution. Particle size analysis is a laboratory
techniques that determine the size range or the average size of the particles in a powder or liquid sample. Its determination is carried out generally in particle technology laboratories. The particle size can have considerable importance in a number of
industries including the chemical, mining, forestry, agriculture, and aggregate
industries.
During
formulation of drugs,
the particle size of drug and powders influences
the subsequent physical performance of the medicine and the pharmacological of
the drug. Powder with different particle sizes have different flow
and compaction properties. This will then alter
the volumes of powder required during tablet
compression. Smaller particles dissolve more quickly and lead to higher suspension
viscosity.
The
size of active ingredients plays a very important role in pharmaceutical
industry, influencing content uniformity, dissolution and absorption rates. It is
necessary to carry out a size analysis using different methods. One of the
method for particle analysis is using microscope as shown in this experiment.
Various samples are examined under microscope and their size and shape is
recorded and compared.
Apparatus
and Materials:
Light Microscope
Spatula
Weighing Boat
Glass Slide
Cover Slip
Newspaper
Powders (MCC, Lactose)
Sands (150mic, 355mic, 500mic,
850mic, various sizes)
Procedures:
1. A small amount of 150micron sand particles is taken out from the
container prepared in the laboratory and put in a weighing boat.
2. Newspaper is put on the table before placing the glass slide.
3. By using a spatula, the sand particles of 150micron is slowly and
carefully placed on the glass slide. (as shown in Figure 1)
Figure
1
4. The sand particles is spread evenly and fairly flat on the surface of
the glass slide before covering it with cover slip.
5. The slide is then examined by using a light microscope under 10 x 10
magnification. (as shown in Figure 2)
Figure
2
6. The particles observed microscopically is recorded and the general shape
for the particular material is determined.
7. The experiment is then repeated by using 355micron sand, 500micron sand,
850micron sand, various size of sand particles, MCC powders and lactose
powders.
Results:
Title:
Sand Particles of 150 micron under Microscope
Magnification:
10 x 10
The particles size of the sand
is very small, almost same in size and having irregular shape. The general
shape for the sand of 150 micron having medium sphericity and sub-rounded.
Title:
Sand Particles of 355 micron under Microscope
Magnification:
10 x 10
The sand particles is bigger
than that of 150 micron and irregular in shape. The general shape for the sand
particles of 355 micron is medium sphericity and sub-angular.
Title
: Sand Particles of 500 micron under Microscope
Magnification:
10 x 10
The sand particles have bigger
size than 150micron and 355micron, irregular in shape but the size is almost
the same. The general shape of sand particles of 500 micron is low sphericity
and angular.
Title:
Sand Particles of 850 micron under Microscope
Magnification:
10 x 10
The sand particles is larger
than the sand particles of 150micron, 355micron and 500micron. The particles
size is irregular but almost with the same size. The general shape of this type
of sand is very angular and low in sphericity.
Title:
Sand Particles of Various Size under Microscope
Magnification:
10 x 10
The shape of the sand
particles is very irregular and larger than other types of sands. The sand
particles are highly angular and very low in sphericity.
Title
: MCC Particles under Microscope
Magnification:
10 x 10
The size of MCC powders are
alomost the same size. The shape of the MCC powders is regular, with round and
rice-like shape.
Title:
Lactose Particles under Microscope
Magnification:
10 x 10
The size of lactose powders is
smaller than MCC powders. The particles exhibit a more constant shape and size.
Lactose has the smallest size compared to others.
Discussion:
In this experiment, different types of sands and
powders are examined using a light microscope. Light microscope is chosen to be
used in this experiment instead of transmission electron microscope or scanning
electron microscope. This is because light microscope is suitable to be used
for particle size range from 0.1 micrometer to 100nanometers. The sands and
powders used in this experiment are lactose powders, MCC powders, 150micron sands, 355micron sands, 500micron sands, 850micron sands and
sands of various sizes
Before observing the sand particles, the sand particles is
spread and dispersed evenly on the slide until it is appeared as a thin layer.
This is to avoid agglomeration and ensure an accurate observation. Based on the
observation, the overall shape of the sand particles are asymmetry. The particle shape can be characterized from low
sphericity to high sphericity, from very angular, angular, sub-angular,
sub-rounded, rounded and well-rounded. While for the powders, the shape is
regular and the size is almost constant. The size analysis is carried out on
two-dimensional image of particles which are generally assumed to be randomly
oriented in 3-dimensional. It is analyzed according to the desired equivalent diameter.
In a case of dendrites, fibres or flakes the particles will orient with their
minimum dimensions in the plane of measurement give the most stable
orientation. All the observations recorded is by the same
magnification so that the comparison between the results can be done clearly
and easily.
The particle size analysis can be done further by using various method
such as projected area diameter, projected perimeter diameter and better by
using Feret’s diameter or Martin’s diameter. 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.
These two methods consider the orientation of
particles, hence this increase the accuracy of the results obtained. Another
advantages of these methods is the particles can be examined individually. Besides,
since it is accessing the three-dimensional image of particle, we can use the
electron microscope that considering the orientation and shape of the image.
Questions:
1. Explain in briefly the various methods that you can use to measure the
diameter of a particle.
Methods for
determining particle size include microscopy, sieving, sedimentation
techniques, optical and electrical sensing zone method, laser light scattering
techniques and surface area measurement techniques. For measurement of the
diameter of a particle, projected area diameter and projected perimeter diameter are methods that can be used. Projected area diameter
is
measured based on the equivalent area to that of projected image of that
particle. Projected area is two-dimensional area measurement of a
three-dimensional object by projecting its shape on to an arbitrary plane. Another 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 and only take into account of 2 dimensions of the particle, thus
inaccurate for unsymmetrical particle.
Methods that considering the orientation of the particle are Martin’s diameter and Feret’s diameter. Both Martin’s diameter and Feret’s diameter are generally used for particle size analysis by optical and electron microscopy. Martin’s diameter is the mean chord length of the projected particle perimeter, which can be considered as the boundary separating equal particle area. While Feret’s diameter can be defined as the distance between the two parallel planes restricting the object perpendicular to that direction. It is therefore 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’s diameter is defined as the distance between two parallel tangential lines rather than planes. Feret’s diameter is used in the analysis of particle size and its distribution, e.g. in a powder or a polycrystalline solid; Alternative measures include Fourier, Krumbein diameter and Heywood diameter.
Methods that considering the orientation of the particle are Martin’s diameter and Feret’s diameter. Both Martin’s diameter and Feret’s diameter are generally used for particle size analysis by optical and electron microscopy. Martin’s diameter is the mean chord length of the projected particle perimeter, which can be considered as the boundary separating equal particle area. While Feret’s diameter can be defined as the distance between the two parallel planes restricting the object perpendicular to that direction. It is therefore 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’s diameter is defined as the distance between two parallel tangential lines rather than planes. Feret’s diameter is used in the analysis of particle size and its distribution, e.g. in a powder or a polycrystalline solid; Alternative measures include Fourier, Krumbein diameter and Heywood diameter.
2. State the best statistical method for each of the samples that you have
analysed.
The best
statistical method is Feret’s diameter. It is
because it gives an average value of diameter in more orientation and a mean diameter value for each particle which is more accurate can be obtained. Electron microscope that considering the orientation and shape of the
image can be used because Feret’s diameter accesses the three-dimensional image of particle.
CONCLUSION:
Every
particles has its own shape and size. In this experiment, by using a
microscope, the shape and size of different types of sands and powders are
analyzed. Most of the particles having shape that are asymmetrical
and irregular. 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. The particle size analysis can be done further by using
Feret’s diameter and Martin’s diameter.
REFERENCES:
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