TITLE: ASSESSMENT ON THE EFFECT OF DIFFERENT CONTENT MATERIALS ON SUSPENSION
FORMULATION
Introduction
A suspension is a disperse
system in which one substance (the disperse phase) is distributed in
particulate form throughout another (the continuous phase) (i.e. at least 2
phases).Drugs that have very low solubility are usefully formulated as
suspensions.The natural tendency of particles towards
aggregation will determine the properties of a suspension. Whether or not a
suspension is flocculated or deflocculated depends on the relative magnitude of
repulsive/attractive forces between particles.
The addition of suspending agents will increase the viscosity of the
vehicle, thereby slowing down sedimentation. Tragacanth used in this experiment
is widely used as suspending agent and is less viscous at pH 4-7.5 and it is
categorize under natural polysaccharides
suspending agents. Suspending agents are added to slow down the rate of
settling of the solid. Suspending agents may be natural polysaccharides, semi
synthetic polysaccharides, clays or synthetic polymers.Some suspensions are
made by adding water to reconstitute manufactured powders when stability is a
problem.
Objective
1. To
investigate the effect on different amount of Tragacanth on suspension
formulation
2. To study
the effect on suspension formulation upon different content materials
Procedure
1. A suspension formulation
of Pediatric Chalk Mixture is prepared by using formula below :
Chalk 3g
Tragacanth 0.1g
Concentrated
Cinnamon Water 0.6 ml
Syrup
BP 15
ml
Double
Strength Chloroform Water 75 ml
istilled
Water, q.s. 150
ml
2. 5 ml of suspension
formulation is poured into the weighing boat and is labeled. The texture,
colour, and clarity is observed and compared.
3. 50ml
suspension was poured into a 50ml measuring cylinder and the height of sediment
formed in the cylinder is measured at interval of 0, 5, 10, 15, 20, 25, 30, 35,
40, 45, 50, 55 and 60 minutes.
4. The rest of the
suspension (95 ml) was poured into 100 ml beaker and the viscosity of the
suspension was measured by the viscometer.
5. 10ml of the suspension was poured into a centrifuge tube.Then,the height
of sediment is determined after centrifugation.(1000rpm, 5 minutes, 25°c).
RESULT:
3. The height of the solid phase suspended
in the cylinder.
Time (min)
|
0
|
5
|
10
|
15
|
20
|
25
|
30
|
35
|
40
|
45
|
50
|
55
|
60
|
Height
(mm)
|
12
|
11.8
|
11.6
|
11.5
|
11.5
|
11.5
|
11.4
|
11.3
|
11.3
|
11.3
|
11.2
|
11.1
|
10.9
|
4. The viscosity of the suspension
Reading
|
1
|
2
|
3
|
4
|
5
|
6
|
Viscosity
|
2.10
|
2.40
|
2.80
|
1.70
|
2.90
|
2.80
|
Average + SD
|
Average : 2.45
SD :
0.47645
|
|||||
5. The height of the solid phase after
centrifuged.
Height (mm)
|
|
Before centrifuged
|
5
|
After centrifuged
|
14
|
Height ratio before and after centrifuged
|
5:14
|
1)
Compare the physical appearance of
suspensions happen and explain.
2) Plot a graph of height of suspended vs time. Explain.
3) Plot a graph of height of suspended v time for the formulation of suspension that containing different Tragacanth. Explain.
4) Describe briefly the mechanism
analysis of viscometer. Plot graph of viscosity of the formulation of
suspension vs Tragacanth content (g). Explain.
Rotational
viscometers use the idea that the force required to turn an object in a fluid,
can indicate the viscosity of that fluid. The viscometer determines the required force for
rotating a disk or bob in a fluid at known speed. 'Cup and bob' viscometers
work by defining the exact volume of sample which is to be sheared within a
test cell, the torque required to achieve a certain rotational speed is
measured. There are two classical geometries in "cup and bob"
viscometers, known as either the "Couette" or "Searle"
systems - distinguished by whether the cup or bob rotates. 'Cone and Plate' viscometers
use a cone of very shallow angle in theoretical contact with a flat plate. With
this system the shear rate beneath the plate is constant to a modest degree of
precision, a graph of shear stress (torque) against shear rate (angular
velocity) yields the viscosity.
GROUP 1 & 5
Reading
|
1
|
2
|
3
|
4
|
5
|
6
|
Viscosity (cP)
|
2.5
|
2.35
|
2.75
|
2.85
|
3.45
|
4.0
|
Average+ SD
|
Average:2.9833
SD:0.6258
|
|||||
GROUP 2 & 6
Reading
|
1
|
2
|
3
|
4
|
5
|
6
|
Viscosity (cP)
|
1.8
|
1.85
|
2.2
|
1.95
|
2.25
|
2.0
|
Average+ SD
|
Average:2.0083
SD:0.1828
|
|||||
GROUP 3 & 7
Reading
|
1
|
2
|
3
|
4
|
5
|
6
|
Viscosity (cP)
|
2.33
|
2.98
|
3.65
|
3.7
|
3.75
|
3.4
|
Average+ SD
|
Average:3.3017
SD:0.5547
|
|||||
GROUP 4 & 8
Reading
|
1
|
2
|
3
|
4
|
5
|
6
|
Viscosity (cP)
|
2.4
|
3.3
|
3.0
|
2.9
|
2.65
|
3.45
|
Average+ SD
|
Average:2.95
SD:0.3924
|
|||||
5 )
Plot a graph of
height of sedimentation formed after centrifuge against the composition of
tragacanth(g). Give your explanations.
Graph the height ratio of the suspension
after centrifuged against the tragacanth content.
Tragacanth content
|
0.0
|
0.1
|
0.3
|
0.5
|
||||
G1
|
G5
|
G2
|
G6
|
G3
|
G7
|
G4
|
G8
|
|
Before
centrifuged
|
24
|
20
|
0
|
5
|
7.9
|
100
|
2
|
1
|
After
centrifuged
|
6
|
12
|
10
|
14
|
1.4
|
1.5
|
18
|
15
|
Height
ratio
|
0.25
|
0.6
|
10
|
2.8
|
0.18
|
0.02
|
9
|
15
|
Average
|
0.425
|
6.40
|
0.10
|
12.0
|
||||
Height
ratio against tragacanth content
6)
What is the function of each material that has been used in preparation
of this suspension? How does the different amount of tragacanth used influence
the physical characteristics and stability of suspension formulation?
Materials
|
Function
|
Chalk
|
As an active ingredient.
|
Tragacanth
|
Act as suspending and thickening
agent.
Prevent sedimentation of suspended
particles.
|
Concentrated Peppermint water
|
As a flavoring agent.
|
Syrup BP
|
Sweetening agent
Cosolvent.
|
Double-strength Chloroform Water
|
As preservative.
Sweetening agent.
|
Distilled water
|
Act as solvent.
|
There are two functions of Tragacanth, as suspending and also
thickening agent. As suspending agent, it will form film around particle and
decrease the attraction between them (involve cohesion force). Tragacanth which
is as thickening agent may increase the solution viscosity which helps to
prevent sedimentation to occur. Its’ viscosity is important for the stability and pourability of
suspensions. This is because suspensions have the least physical stability
amongst all dosage forms due to its’ cake formation. Therefore, as the
viscosity of the dispersion medium increases, the terminal settling velocity
decreases thus the dispersed phase settle at a slower rate and they remain
dispersed for longer time yielding higher stability to the suspension. At the
same time, the pourability will decrease and inconvenience to the patients for
dosing increases. Thus, the viscosity should be maintained at a preferred
range.
If we increase the amount of tragacanth, the viscosity of
suspension increases. As the viscosity increase, the terminal settling velocity will
decreases making the dispersed phase settle at a slower rate. The phase remain
dispersed for a longer time. Hence,
the stability of the suspension increases. On the other hand, the viscosity can
determine the pourability of suspension. High viscosity in suspension will lead
to difficulty to be poured. That’s why the viscosity should be maintained at a
preferred range.
Discussion:
A
pharmaceutical suspension may be defined as a coarse dispersion containing
finely divided insoluble material suspended in a liquid medium.
The
physical chemist defines the word “suspension” as two-phase system consisting
of an undissolved or immiscible material dispersed in a vehicle (solid, liquid,
or gas).
Generally
pharmaceutical suspensions contain aqueous dispersion phase however in some
cases they may be an oily or organic phase. The suspensions have dispersed
particles above the colloidal size that is mean particle diameter above 1µm.In
this experiment, the suspension contain aqueous dispersion phase.
In
the suspension, we have used different amount of tragacanth. As the amount of
Tragacanth used increased, the suspension will become more viscous and stable
against coagulation. Tragacanth may increase the viscosity of the aqueous
vehicle and thus slow the rate of sedimentation of the particles but they will
also form adsorbed layers around the particle so that the approach of their
surfaces and aggregation to the coagulated state is hindered. Therefore, there
will be less flocculation and once the sedimentation occurs; the suspension
becomes more difficult to redisperse.
There are
several factors that we recognized that may lead to error while doing this
experiment, which are:
1.
Difficulties to take the reading of the height
of solid suspended in the measuring cylinder because the white sedimentation is
hardly to be seen in a cloudy suspension.
2.
Suspensions tend to be quite viscous, so
measurements using a viscometer can be quite slow.
3.
The suspension is contaminated with living
cells. The Coulter Counter method counts both living and dead cells which may
lead to error.
Conclusion:
The increasing
weight of Tragacanth makes the texture become more smooth and viscous. Any
increase of the suspension viscosity due to high amount of Tragacanth will
prevent sedimentation formation and yet any caking formation. Thus, a more
stable suspension can be formed with a higher amount of Tragacanth used.
References
1)
Michael E.Aulton, Aulton’s Pharmaceutics The Design And
Manufacture of Medicines, third edition, 2007, Churchill Livingstone Elsevier
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