DATE OF EXPERIMENT: 7/11/2016
PRACTICAL 4: Particle size and shape analysis
TITLE: Particle size and shape analysis using microscope
OBJECTIVE(S):
1. To analyse on the size and shape of five different types of sands, Microcrystalline Cellulose(MCC) and lactose
2. To determine the general shape for the particular material
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. Different particle sizes of solid have different flow and packing properties which alter the volume of powder during each tablet compression event. The particles that have small dimension will tend to increase the rate of dissolution.
For example, microcrystalline cellulose (MCC) and lactose is use as diluents for drug manufacturing. These diluents are added as additives which may be used as binders and disintegrants (help the tablet breaks apart in the digestive system). Thus the particle size of these diluents play important role on dissolution rate and formulation of drugs.
The particle shape and size can be analysed by many methods. Microscopic analysis is the most widely used method in this case. It can determine the diameter, shape, and surface area that cannot be determined with the bare eye. It is an excellent technique because we can look at the particle directly and is relatively cheap .The disadvantages of using microscope to analyse the shape and size of particle is the elaborate sample preparation is slow and it is not suitable for quality control.
In this experiment, five size of sands (various size, 150µ, 355µ, 500µ and 850µ) and two powders (lactose and MCC) are given to be analysed and observed.
APPARATUS:
Microscope, weighing boat, microscope slide, spatula
MATERIALS:
Sand with particle size of (150µ, 355µ, 500µ, 850µ), sand with various sizes, MCC and lactose
PROCEDURE:
1. Sands with sizes of 150µ, 355µ, 500µ, 850µ (sand with various sizes), MCC and lactose were placed in the different weighing boat by using spatula. The weighing boats were labelled according to the content.
2. The microscope was set up and ready to be use.
3. Lactose powder was scattered on the glass slide using a spatula
4. The lactose was observed under the microscope using 10X magnification followed with 40X magnification.
5. The particles were observed microscopically and the shape was determined.
6. Steps 3 to 5 were repeated by using MCC powder, sand with various size and sands with size 150µ, 355µ, 500µ and 850µ
OBSERVATION
Lactose
10X magnification
40X magnification
Microcrystalline cellulose (MCC)
 |
| 10x magnification |
 |
| 40x magnification |
DISCUSSION
We are using light microscope to determine the various shape and size of different types of sands and powders. For the size of sands, we are using 150µm, 355µm, 500µm, 850µm and various size while for the type of powders are Microcrystalline cellulose (MCC) and lactose. All these substances have been put on the slide and directly observed by using a compound light microscope.
From this practical, it is found that the overall shape of the sands and powders are asymmetrical. One of the methods used to measure a particle is the projected area diameter. We measured based on the equivalent area to that projected image of that particle. Another method is the projected perimeter diameter. It is based on the circle having the same perimeter as the particle. Both of the methods do not account the 3 dimensional shape of particle (orientation). They only consider the 2 dimensions of the particle, thus it is inaccurate for unsymmetrical particle.
For the measurement of the diameter of particle, we can use Feret’s and Martin’s diameters. These are the statistical diameters which are averaged over many different orientations to produce a mean value for each particle diameter. Martin’s diameter is the mean chord length of the projected particle perimeter, which is the boundary separating equal particle while Feret’s diameter is the mean distance between two parallel tangents to the projected particle perimeter. For analysis of particle size by using compound light microscope the analysis is carried out on two-dimensional images of particle. It is normally assumed to be oriented randomly in three dimensional. This assumption is considered valid for many cases. However for dendrites, fibres or flakes it is very unlikely that the particles will orient with their minimum dimensions in the plane of measurement. Therefore, size analysis is carried out by estimating that they are viewed in their most stable orientation. Thus overestimation of size may occur, because the largest dimensions of the particle will be observed as the smallest dimension which will most often orientate vertically. The two dimensional images are analysed according to the desired equivalent diameter.
Disadvantages of this method include it not being suitable for quality control. The operator time required to analyse a sufficient number of particles to be representative is prohibitive except in the highest value applications. This is an offline method of particle characterisation with very limited throughput which may make it unsuitable for a number of applications. However, the ability to analyse and characterize particle size and shape can significantly improve the manufacturing efficiency and product performance. Thus, we can use microscopy and image analysis to characterize particle shape, size and volume distribution.
CONCLUSION:
The size and shape of five different types of sands, Microcrystalline Cellulose(MCC) and lactose can be analysed using compound light microscope and each particles are differ to other. The overall distribution of shape and size of all particles are asymmetrical and irregular.
REFERENCES:
2. https://www.innopharmalabs.com/tech/applications-and-processes/particle-characterisation
QUESTION:
1. Explain in brief the various statistical methods that can you use to measure diameter of a particle.
The first is by using Feret’s and Martin’s diameter which are averaged over many different orientation to produce a mean value for each particle diameter. Feret’s diameter refers to 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 which can be considered as the boundary separating equal particle areas
Influence of particle orientation on statistical diameters. The change in Feret’s diameter is shown by distances d and Martin’s diameter correspond to the dotted lines in the middle part of each image
Besides, Fourier analysis can be one of the methods 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.
Lastly, projected area can be used 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.
2. State the best statistical method for each of the samples that you have analysed.
The best statistical method for each of the samples analysed is by Feret’s and Martin’s diameter because both of the parameters give the average diameter over many different orientations to produce a mean value for each particle diameter. This will give an average value which is more accurate.
