Aim:
To
determine the particle size and the size distribution of lactose and
microcrystalline cellulose (MCC) by using sieves.
Introduction:
A sieve, or sifter, is a device for separating
wanted elements from unwanted material or for characterizing the particle size
distribution of a sample, typically using a woven screen such as a mesh or net. The word "sift" derives from
'sieve'. Sieves are commonly used to break down agglomerates, and determine the
size and size distribution of a particular powder. Sieve nest is used to
determine the particle size and the size distribution of both lactose and
microcrystalline cellulose (MCC) which are excipients that commonly used in
tablet formulations.
Apparatus / Materials:
Sieve
nest
Microscope
Slides
Sands
Electronic
balance
Chemicals:
Lactose
Microcrystalline
cellulose (MCC)
Procedure:
A.
Determine the
particle size and the size distribution by using sieve nest
1. 100g of lactose is
weighed by using electronic balance.
2. The sieve nest is
prepared in descending order. Largest diameter on the top and smaller diameter
at the bottom.
3. The lactose powder is
placed at the uppermost sieve and the sieving process is allowed to proceed for
20 minutes.
4. The powder collected
at every sieve is weighed upon completion and the particle size distribution is
plotted I the form of histogram.
5. The above procedures
are repeated by substitute the lactose powder with Microcrystalline cellulose
(MCC)
B.
Particle size and
shape analysis using microscope
1. 5 different types of
sands, lactose powder and microcrystalline cellulose (MCC) powder is analysed
by using microscope.
2. The size and the
shape of the particles are examined.
3. The particles
observed are sketched microscopically.
4. The general shape for
the particular material is determined
Result:
Size of aperture (µm)
|
Particle size range, x (µm)
|
MCC
|
Lactose
|
Weight (g)
|
Weight (g)
|
||
<53
|
0<x<53
|
7.4928
|
3.7975
|
53
|
53<x<150
|
85.4162
|
93.7731
|
150
|
150<x<200
|
3.3123
|
1.4084
|
200
|
200<x<300
|
1.8172
|
0.8361
|
300
|
300<x<425
|
0.1300
|
0.0091
|
425
|
>425
|
0.0823
|
0.0059
|
Total
|
98.2508
|
99.8301
|
|
Questions:
1.
What are the average particle size for both lactose and MCC?
The average particle size for both lactose and MCC are 50- 150 µm.
2.
What other methods can you use to determine the size of particle?
The
other methods that can be used to determine particle size are
a.
microscope
methods
b.
coulter
counter
c.
laser
light scattering method
d.
dynamic
light scattering method
e.
sedimentation
method
3.
What are the importance of particle size in a pharmaceutical formulation?
Particle size
in a pharmaceutical formulation is important in achieving optimum production of
efficacious medicines especially in pharmaceutical phase. It also can influence
the bioavailability and activity of drug. Particle
size may also affect the behaviour of a formulation during processing and,
ultimately, its content uniformity. In direct compression tableting, for
example, particle size can influence segregation behaviour, the ease with which
powder flows through the press and the compressibility of a formulation.
Particle size also has a
critical effect on the content uniformity of solid dosage forms, and it often
matters to create the right relationship between the size and densities of API
and excipient particles.
Similarly, the size of
particles can affect viscosity and flow, and increasing the polydispersity of
particle sizes in a powder can improve its flow properties. For example, for
many powders subject to flow in an industrial process, a bimodal distribution
of particle sizes ensures easier flow during processing.
In products where viscosity is
important, there is often an optimum particle size distribution (psd) that
gives a minimum viscosity whilst maintaining the volume fraction of particles.
Of course, the psd will also have a direct influence on the texture and feel of
the finished product in terms of both efficacy and consumer perception.
Discussion:
In
this experiment, we observed two materials which are microcrystalline cellulose
(MCC) and lactose respectively. We used the sieving method in this experiment.
Sieve nest is required so that we are able to determine the particle size and
the size distribution of both powders. The sieve nest is arranged in descending
order from top to bottom (from largest diameter to smallest diameter). This means, the sieve
that have diameter of aperture of 500 µm
will be placed at the top followed by 425 µm, 300 µm, 150 µm, and 45 µm.
According to the result, most of the MCC fall in the
sieve nest which is ranges that less than 150µm. This means that most of
the particle size of MCC is smaller than 150 µm. At another experiment, most of
the lactose fall in the sieve nest which is ranges that less than 150µm. This
means that most of the particle size of lactose is smaller than 150µm. Both MCC
and lactose are different materials so they will have different physical
properties. In this experiment, MCC has been affected more than lactose
during the physical vibration that applied on them because the hardness surface of particle
is the one that contribute to the reduction of particle size. The result of
this experiment is considered not fully accurate since the weight of the MCC
and lactose sum up is not equal to 100g. This is because there are some powders
left in the sieves at the end of the experiment. Moreover, small amount of
powders spilled out from the container when we moved it from one place to
another place. These factors also contribute to the inaccurate results of the
experiment.
So, in order to obtain a more
accurate result, we should clean up the sieve to prevent soil particles stuck
in the openings which will affect the accuracy of the experiment. Besides, we
also have to prepare a suitable size of container to load the powders. If the
size of the container is not big enough, powders will spill out. Before we
conduct the experiment, we must check the machine whether it is in good
condition or not to avoid powders spill out during the physical vibration.
Conclusion:
In the nut shell, sieving is one of
the methods that can used to determine size and particle size distribution of the particles. The distribution of particles size
are able to be analysed after conducting this experiment especially in
achieving optimum production of efficacious medicines in pharmaceutical phase.
Most particles size of lactose is in the range of 50 - 150µm. While as for MCC,
most particles size is in the range of 50 - 150µm.In conclusion, lactose has
bigger particle size than that of MCC.
References:
- www.geog.ucl.ac.uk/about-the.../support...methods/.../sieving-method
- http://www.pharma-excipients.com/micro-crystalline-cellulose.html
- http://www.pharmaceutical-int.com/article/particle-size-is-important-particle-analysis-techniques.html
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