Evaluation on the effect of different composition of tragacanth on the characteristics of a suspension.
AIM:
To
study the effects induced by the use of different
Tragacanth content on a suspension formulation.
INTRODUCTION:
Suspension
formulation is a type of dispersed system where the solid molecules do not
dissolve homogenously in the liquid phase. A good suspension must stay in
homogenous state after being shaken, be easy to pour out from the container and
having a uniform solid particle size and also attractive taste and texture.
Precipitation formed from the storage must be easily dispersed again after
shaking and the dispersion formed must be homogenous.
Normally,
suspension composed of active ingredient (solid phase) dispersed in the liquid
carrier, wetting agent, flavouring agent and colouring agent. Wetting agent
(eg: Tragacanth) is used to reduce the surface tension between solid particle
and liquid. Suspension is classified as coarse suspension where the particle
diameter is more than 1 µm, or colloidal suspension where the particle size is
less than 1 µm. In pharmaceutics, suspension is used to improve the stability,
the taste and the bioavailability of the active ingredient.
MATERIALS AND APPARATUS:
Apparatus:
Weighing instrument, weighing boat, mortar and pestle, 150ml plastic bottle, 50ml measurable cylinder, 200ml measurable cylinder, 1 set of 1 ml pipette and pipette
bulb, 1 centrifugator tube 15 ml, 100 ml beaker, Coulter counter instrument, Centrifugator, Viscometer
Materials:
Chalks, Tragacanth, Concentrated Peppermint Water, Syrup BP, Double-strength chloroform water, Distilled water
PROCEDURES:
1) 1
formulation of Pediatric Chalk Mixture (150 ml) are prepared by the following
formulation.
Chalk
|
3 g
|
Tragacanth
|
(referred
to the Table 1)
|
Concentrated
Cinnamon Water
|
0.6 ml
|
Syrup
BP
|
15 ml
|
Double
Strength Chloroform Water
|
75 ml
|
Distilled
Water, q.s.
|
150 ml
|
Table 1
Pediatric
Chalk Mixture
|
Group
|
Tragacanth
(g)
|
I
|
1,5
|
0.0
|
II
|
2,6
|
0.1
|
III
|
3,7
|
0.3
|
IV
|
4,8
|
0.5
|
3) 50 ml
of suspension are poured into 50 ml measurable cylinder. Height of the solid
phase precipitated in the cylinder is measured at the interval of 0, 5, 10, 15,
20, 25, 30, 40, 50 and 60 minutes.
4) The rest
of the suspension (95 ml) are poured into 100 ml beaker and the viscosity of
the suspension are measured by a viscometer.
5) 10 ml
of suspension are poured into centrifugator tube and the height of the solid
phase is measured after centrifugation (1000rpm, 5 minutes, and 25°C).
RESULTS
DISCUSSION:
1. Compare the physical appearance of suspension formed and explain.
Pediatric
chalk mixture
|
I
(Group
5)
|
II
(Group
6)
|
III
(Group
7)
|
IV
(Group
8)
|
Tragacanth
(g)
|
0.0
|
0.1
|
0.3
|
0.5
|
Texture
|
More dilute
|
Dilute
|
Concentrated
|
More concentrated
|
Clarity
|
Clear
|
Less clearer
|
opaque
|
More opaque
|
Colour
|
Colourless
|
Milky, chalky
|
White
|
White
|
Among all dosage forms, suspensions have
the least physical stability due to sedimentation and cake formation. A
well-formulated suspension needs to be easily resuspended by normal agitation
and remain in that condition long enough for accurate dosing. In order to do
so, it needs suspending agent such as tragacanth which forms film around
particle and decrease the interparticle attraction. Tragacanth also gives
viscosity to the solution whereby it is of great importance for stability and
pourability of suspensions. For instance, when the viscosity of the dispersion
medium increases, the drug particles settling velocity decreases thus they
remain dispersed for longer time resulting in higher stability and increase in
dosing accuracy. However, if the viscosity of the suspension is too high, the
pourability decreases and might cause inconvenience to the patients.
Different group uses different
concentration of tragacanth in the experiment. For group 5, the texture of the
suspension remains diluted and rough due to the absence of tragacanth. For
group 6, 7, and 8, the amount of tragacanth added is increased gradually and
results in the more concentrated form of suspension. For the suspension without
tragacanth, the texture remains diluted because most of the chalks have undergo
sedimentation and what we observed is just the dispersion medium. For
suspension with tragacanth, the texture becomes smoother and more viscous.
However, amount of tragacanth cannot be too high because it will be too viscous
to agitate and pour.
2. Plot graph height of sedementation against time. Give explanation.
The graph shows the relationship between
sediment height (mm) and time (min). From the graph, it is clearly that the
height of sediment decreases gradually over time until it reaches the height
where equilibrium is reached. In this experiment, tragacanth is totally absent.
Hence, this results in immediate sedimentation due to instability and a
flocculated system is produced.
3. Plot a graph of height of ratio of sediment as a result of
centrifugation vs. amount of tragacanth. Give explanation.
Time
(min)
|
Average
height of precipitate (mm)
|
|||||||||||||
0
|
5
|
10
|
15
|
20
|
25
|
30
|
35
|
40
|
45
|
50
|
55
|
60
|
||
Mass of
tragacanth (g)
|
0.0
|
0
|
100
|
70
|
60
|
60
|
60
|
60
|
60
|
60
|
60
|
60
|
60
|
60
|
0.1
|
0
|
20
|
50
|
50
|
60
|
60
|
70
|
70
|
70
|
80
|
80
|
80
|
80
|
|
0.3
|
121
|
121
|
121
|
120
|
120
|
119
|
119
|
119
|
119
|
119
|
119
|
119
|
119
|
|
0.5
|
0
|
100
|
200
|
200
|
200
|
200
|
300
|
300
|
300
|
300
|
300
|
300
|
300
|
|
Based on the plotted
graph, in the absence(0.0g) of tragacanth we can observed that from 0 to 10th
minutes, the sharp increase line provided. It is due to absent of suspending
agent that cause the particles flocculate and settle down at the bottom. In the
10th to 15th minutes the graph slowly decrease, because
as the particles flocculate, it become compact sediment and caking formed.
After 15th minutes the graph reached equilibrium. As the particles
become compact, the spaces are filled so there are no available spaces for the
particles to fill in. The height of sedimentation remains same.
In the 0.1g of
tragacanth, the graph increases gradually until 45th minutes it
achieved equilibrium. The presence of suspending agent adsorb onto the
particles cause the viscosity of the suspension increase and the dispersion
remains. Then the particles start to flocculate and sediment at the bottom
cause caking formed.
For 0.3g of tragacanth,
as the increasing amount of tragacanth its increase the suspension to occur.
The longer time takes for the particles to flocculate, sediment and caking. The
graph show it increase in small amount then achieve the equilibrium. The
stability of suspension is higher compare to
0.1g of tragacanth.
The 0.5g of tragacanth,
which have the highest amount of suspending agent and have the highest
stability among the rest samples. The graph shows that it has the sharp
increase until the equilibrium reached at 25th minutes. High amount of
tragacanth interact with the gravity force resulting in no formation of caking
and allow the particles to remain suspended.
4.Explain the analysis mechanism of
the viscometer. Plot a graph of the viscosity of the suspension versus the
content of Tragacanth. Give the explanation.
Viscometer is a device that used to measure and
determines the viscosity of the fluid. A rotational viscometer is used during
this experiment. When immersed in a sample fluid, rotational
viscometer senses torque required to rotate a spindle at constant speed to
calculate the viscosity of the fluid. Besides, this measured torque is
proportional to the dynamic viscosity. Different viscosity of sample fluid
requires different type of the spindle to have an accurate measurement on the
viscosity. A more viscous suspension should use a thinner spindle and vice
versa. Typical rotational viscometer consists of one cylinder rotating inside
another stationary cylinder. The sample fluid will occupy the gap in between
the two cylinders which will in turn resist rotation. The torque required to
maintain constant rotational rate while overcoming viscous resistance and it is
correlated with viscosity. Thus it can be said that the dynamic viscosity is
proportional to the measured torque. The continuous changes in magnetic field
cause the rotor magnet to spin. Therefore, as there are no bearings to speak
of, viscosity measurement is a direct correlation between fluid friction and
applied torque. This measured data is then converted to a viscosity value and
output to the users. The standard rotational viscometer is common used for
measuring the viscosity of non-Newtonian fluids either in chemical or food
industries.
Result from other groups for different
amount of Tragacanth:
Amount
of Tragacanth (g)
|
Readings
|
Viscosity
(cP)
|
Viscosity
(cP) (Average ± SD)
|
0.0
|
1
|
2.50
|
3.03±0.83
|
2
|
3.60
|
||
3
|
3.40
|
||
4
|
2.20
|
||
5
|
2.10
|
||
6
|
4.40
|
||
0.1
|
1
|
5.00
|
4.33±0.75
|
2
|
3.00
|
||
3
|
4.00
|
||
4
|
5.00
|
||
5
|
5.00
|
||
6
|
4.00
|
||
0.3
|
1
|
7.00
|
6.58±0.73
|
2
|
6.50
|
||
3
|
6.00
|
||
4
|
6.00
|
||
5
|
6.00
|
||
6
|
8.00
|
||
0.5
|
1
|
3.00
|
4.90±1.12
|
2
|
4.70
|
||
3
|
5.90
|
||
4
|
4.00
|
||
5
|
5.90
|
||
6
|
5.90
|
Amount of Tragacanth (g)
|
0.0
|
0.1
|
0.3
|
0.5
|
Viscosity (cP)
(average±SD)
|
3.03±0.83
|
4.33±0.75
|
6.58±0.73
|
4.90±1.12
|
From the result that we obtained
from the experiment, the graph plotted shown that the viscosity of the
suspension increases gradually with the increase amount of Tragacanth added.
The viscosity value increased with amount of tragacanth. However, there is a
point show some error, which is when the added Tragacanth is 0.5g (Formulation
Iv). It should show highest viscosity as it have most amount of
tragacanth. This is mostly due to
several errors during the experiment, such as the incorrect preparation of suspension
or the incorrect amount of Tragacanth added. Besides, the technical error may
be due to incorrect usage of viscometer and thus the results that we obtained
are inaccurate. All in all, we can conclude that the viscosity of the
suspension is proportional to the amount of suspending agent added into the
system.
Formulation IV is the most viscous suspension
in this experiment with the 0.5g of Tragacanth. The least viscous suspension is
Formulation I which without any Tragacanth added into it. Tragacanth is a
suspending agent that is used to suspend the chalk powder in suspension. When
the amount of Tragacanth in a suspension increases, the viscosity of the system
is also increasing in a gradually manner. Thus, a more stable suspension can be
formed.
6. Plot a graph of height of ratio of
sediment as a result of centrifugation vs. amount of tragacanth. Give
explanation.
Amount of tragacanth
|
Group
|
Height (cm)
|
Average height ratio
|
||
Before centrifugation
|
After centrifugation
|
Ratio
|
|||
0.0g
|
1
|
27
|
12
|
0.444
|
0.285
|
5
|
80
|
10
|
0.125
|
||
0.1g
|
2
|
75
|
10
|
0.133
|
0.486
|
6
|
80
|
67
|
0.838
|
||
0.3g
|
3
|
80
|
74
|
0.925
|
0.591
|
7
|
82
|
21
|
0.256
|
||
0.5g
|
4
|
80
|
60
|
0.750
|
0.497
|
8
|
74
|
18
|
0.243
|
||
In this experiment, we
can see that when the weight of the tragacanth increases, the ratio of the
height of sediment will increase as well. Centrifugation is a separation
process which uses the action of centrifugal force to promote accelerated
settling of particles in a solid-liquid mixture. Two distinct major phases are
formed in the vessel during centrifugation are the sediment or chalk particles and
the centrifugate which is the supernatant liquid.
Theoretically, the
larger amount of tragacanth used, the lower the height ratio of sedimentation. When
the weight of tragacanth increases, the height of the sediment will decrease.
The formation of the sediment is due to the instability of the suspension, the
suspension that contains more tragacanth will be more stable and less sediment
will be formed after centrifugation. Tragacanth acts as suspending agent and
thickening agent. It increases the viscosity of the solution, which is
necessary to prevent sedimentation of the suspended particles.
However, this experiment does not obey
the theory except for 0.5g tragacanth. This may due to errors that occurred
during the experiment. Initially, when there is no tragacanth being introduced
into the suspension, the height ratio of sedimentation is 0.285. Then, the
height ratio for 0.1g and 0.3g are 0.486 and 0.591 respectively. However, the
height ratio decreases when a larger amount of tragacanth is being used, that
is 0.5g.
7. What is the function of each ingredient used in the
preparation of this suspension? How the use of different Tragacanth content
influences the physical characteristics and stability in a suspension
formulation?
Chalk powder does not dissolve in water.
Chalk forms a suspension which settles to the bottom after some time.
Tragacanth is a suspending agent that acts as viscosity enhancer. It also acts
as a thickening agent. In this experiment, Concentrated Peppermint Water has
been used as a flavoring to mask the unpleasant taste. Syrup BP is used as a
sweetening agents and flavors to make the suspension more palatable. Double
Strength Chloroform Water is used as vehicle, preservative and also gives some
flavoring. Distilled water is the vehicle for this suspension.
The use of different Tragacanth content
influences the physical characteristics and stability of the suspension
formulation. The increasing of Tragacanth will cause viscosity of the
suspension to increase. Thus, the higher viscosity will prevent sedimentation of the suspended particles as per Stoke’s’s law.
In addition, high Tragacanth also will make the suspension to become thicker
and difficult to be poured. The stability of suspension with high Tragacanth is
higher than suspension with lower Tragacanth.
CONCLUSION:
The height
of sediment formed decrease with the increase of Tragacanth content. By
increasing the amount of Tragacanth used, the viscosity of the suspension also
will be increased.
REFERENCES:
3.
Banker, G.S. & Rhodes, C.T. 1990. Modern
pharmaceutics. 2nd Ed. New York: Marcel Dekker.
4.
Aulton, M.E. 2002. Pharmaceutics: The
science of dosage form design. Edinburgh: Churchill Livingstone
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