Title
Assessment of the Effects of Different Compositions of
Ingredients Used on the Characteristics of a Suspension Formulation
Objective
To study the
effect of the composition of tragacanth on the texture, clarity and the
colour of the suspension, the rate of
sedimentation and viscosity of the suspensions of different compositions.
Introduction
A suspension is a type of disperse system where the
insoluble solid particles are dispersed homogenously in the liquid phase. A
good suspension must be in a homogenous form after shaking, easily poured from
the container, has a uniform solid particle size and possess better texture and
feel. Sediments that are formed upon storage have to be easily redispersed
after shaking, forming homogenous suspension.
In
general, suspension comprises an active ingredient (solid phase) in a liquid
carrier, a wetting agent, flavouring and colouring agents and preservatives.
The function of a wetting agent such as tragacanth is to reduce the interfacial
tension between the solid particles and the liquid. Suspension can be
classified as a coarse suspension where the diameter of the particles is more
than 1 µm or as a colloidal suspension where the particle size is less than 1
µm. In pharmaceutical practice, suspension is used to improve the stability of
the active ingredient, taste, and bioavailability.
Apparatus
and Material
I. Apparatus
Weighing
balance
A
set of pipette (1ml) and bulb-pipette
1
weighing boat
1
centrifugation tube 15ml
A
set of mortar and pestle
1
beaker 100ml
Plastic
bottle 150ml
Centrifugation equipment
Measuring
cylinder 50ml
Viscometer
A
measuring cylinder 200ml
II. Materials
Chalk Syrup
BP
Tragacanth Double-strength
Chloroform Water
Concentrated
Peppermint Water Distilled
water
Procedures
1. A
suspension of Paediatric Chalk Mixture (150ml) is prepared using the
formulation below:
|
Chalk
3g
Tragacanth
Refer to table below
Concentrated Peppermint Water
0.6mL
Syrup BP
15mL
Double Strength Chloroform Water 75mL
Distilled Water, q.s.
150mL
|
|
Paediatric
Chalk Mixture
|
Group
|
Tragacanth
(g)
|
|
I
|
1, 5, 9
|
0.0
|
|
II
|
2, 6,
10
|
0.1
|
|
III
|
3, 7,
11
|
0.3
|
|
IV
|
4, 8,
12
|
0.5
|
 |
| Double Strength Chloroform Water |
 |
| Tragacanth gum |
 |
| Concentrated Peppermint Water |
 |
| Syrup BP |
 |
| Chalk |
2.
Some of the suspension formed (5ml) is poured into the
weighing boat and labelled. State and compare the texture, clearness and colour
of the suspension formed.
3.
50ml of suspension formed is poured into the 50ml
measuring cylinder and the height of the solid phase sediment in the cylinder
is measured at intervals of 0, 5, 10, 15, 20, 25, 30, 40, 50 and 60 minutes.
4.
The remaining suspension (95ml) is poured into a 100ml
beaker and viscosity of the suspension formed is determined using a viscometer.
5.
10ml of suspension is poured into a centrifugation
tube and the height of the solid phase formed after centrifugation (1000rpm, 5
minutes, and 25°C) is determined.
Result and Discussion
1.
Compare
the physical appearance of the suspension formed and explained.
|
Physical characteristic
|
Paediatric Chalk Mixture
|
|||
|
I(group 1,5)
|
II(group 2,6)
|
III(group3,7)
|
IV(group4,8)
|
|
|
Texture
-smoothness
-viscosity
-redispersibility
|
|
|||
|
+
|
++
|
+++
|
++++
|
|
|
+
|
++
|
+++
|
++++
|
|
|
++++
|
+++
|
++
|
+
|
|
|
Clarity
|
Less cloudy
|
Moderate cloudy
|
opaque
|
opaque
|
|
Colour
|
white
|
white
|
white
|
white
|
|
Layer
|
2 layer
|
1 layer
|
1 layer
|
1 layer
|
From
our observation, Suspension IV has the highest viscosity and has the smoothest
appearance followed by Suspension III, II and I. This is due to highest amount
of tracaganth added to the suspension IV. Tragacanth , a suspending agent where
the chalk particles are dispersed more homogenously in suspension with higher
amount of tragacanth. Thus a more smooth suspension will be formed by adding
more tragacanth into suspension. Besides, tragacanth is partly soluble in
water, in which it swells to gelatinous mass forms viscous solution with water.
Due to this factor, higher amount of tragacanth will form more viscous solution
such as Suspension IV.
While,suspension
I is the easiest to be redispersed followed by Suspension II, III and
Suspension IV. This is due to deflocculated system formed after adding
suspending agent to suspension. In a deflocculated system, the dispersed
particles will remain as discrete units and settling will be slow. The slow
rate of settling prevents entrapment of liquid within the sediment thus become
compact and can be very difficult to be redispersed. The higher amount of
tragacanth added, the particles will become more deflocculated. Flocculated
system such as Suspension I will be more easily to be redispersed. It will lead
to rapid rate of sedimentation, forming porous sedimentation. This structure of
sedimentation will entrapped a large amount of the liquid phase which aid in
redispersibility. Settling of particle is faster in Suspension I, supernatant quickly
becomes clear compare to other suspension. Suspension IV will remain in the
most cloudy form compare to other suspensions as the settling rate is slow.
The
colour of all suspensions formed is white. This is because of existence of
chalk powder which is in white colour as it is dispersed throughout the
suspension.
2. Graph UV absorption versus time.
The graph above shows the sedimentation height of a
suspension (Pediatric Chalk Mixture type II) which is
formulated with 0.5g Tragacanth
powder. According to this graph, the suspension does not contain any sediment
at the beginning of the experiment. However, as the time passes, sedimentation
will start to form. This is because the forces of interaction between the
inter–particular attractive forces are stronger than the inter-particular
repulsive forces of the Tragacanth
powder on suspension.
From the time 0 to 55minutes, no precipitation can be observed on the
suspension. The suspension was stable over period of 55minutes. On 55minutes
and onward, increase in the height of precipitate was observed. Increase in the
height of precipitate was record. From
the graph above, the height of precipitation was 0 over a period of time. This
probably caused by the amount of the suspending agent used in the suspension is
enough to suspend the particle or drug for a longer time.
3.
Plot a graph of
height of sedimentation against time for the formulations of suspension with
different contents of Tragacanth. Discuss.
|
Time(min)
|
Average sediment height(mm) (X
 SD) |
|||||||||||||
|
0
|
5
|
10
|
15
|
20
|
25
|
30
|
35
|
40
|
45
|
50
|
55
|
60
|
||
|
Tragacanth contents(g)
|
0.0
|
47.50
±
67.1751
|
20
±
2.8284
|
16.5
±
6.3640
|
14.5
±
3.5355
|
14
±
2.8284
|
13.5
±
2.1213
|
13
±
1.4142
|
13
±
1.4142
|
13
±
1.4142
|
13
±
1.4142
|
13
±
1.4142
|
13
±1.4142
|
13
±
1.4142
|
|
0.1
|
11.95
±
0.07071
|
11.85
±
0.7071
|
11.7±
0.1414
|
11.6±
0.1414
|
11.6±
0.1414
|
11.45±
0.7071
|
11.3±
0.1414
|
11.2±
0.1414
|
11.05±
0.3536
|
11.0±
0.4243
|
10.9±
0.4243
|
10.35±
0.7906
|
10.15±
0.7906
|
|
|
0.3
|
0
±
0
|
4.5
±
6.3640
|
8
±
4.2426
|
8
±
4.2426
|
11
±
1.4142
|
11.5±
2.1213
|
19
±
8.4853
|
32
±
25.4558
|
32
±
25.4558
|
32
±
25.4558
|
34.5±
28.9914
|
34.5
±
28.9914
|
34.5±
28.9914
|
|
|
0.5
|
0
±
0
|
1.25±
0.3536
|
4.5
±
0.7071
|
8.5
±
0.7071
|
10
±
0
|
13
±
2.8284
|
16.5±
2.1213
|
18
±
2.8284
|
19.5±
2.1213
|
21
±
1.4142
|
21
±
1.4142
|
21
±
1.4142
|
21
±
1.4142
|
|
The graph above shows the relationship of height of
sedimentation with time in different suspension with different amount of
tragacanth. Based on the graph, the
higher the tragacanth content, the greater amount of sediment formed. This is
incorrect because theoretically, the height of sediment decreases as the weight
of tragacanth increases. Thus, the suspension with higher tragacanth content
should form less sediment. This is because tragacanth is a suspending agent to
stabilize the suspension and reduce sedimentation by producing a deflocculated
system. A suspension with ideal amount of tragacanth would be very stable,
sedimentation rate slow and redisperse easily once shaken. The graph contains
several errors which may be due to the following reasons: calculation mistakes,
incorrect weighing of tragacanth, presence of impurities.
4. Describe
briefly the mechanism of analysis of viscometer. Plot a graph of viscosity
versus weight of Tragacanth (g). Give explanation.
|
Viscosity (cP)
|
1
|
2
|
3
|
4
|
5
|
6
|
Mean ± SD
|
|
Group 1
|
1.9
|
1.8
|
2.0
|
3.0
|
3.4
|
4.2
|
2.72 ± 0.89
|
|
Group 2
|
1.5
|
1.3
|
1.6
|
1.2
|
1.6
|
1.2
|
2.45 ± 0.36
|
|
Group 3
|
3.4
|
3.7
|
3.8
|
3.9
|
4.0
|
3.8
|
3.77 ± 0.47
|
|
Group 4
|
2.3
|
3.4
|
2.7
|
3.2
|
2.8
|
3.5
|
2.98 ± 1.03
|
|
Weight of
Tragacanth (g)
|
0.0
|
0.1
|
0.3
|
0.5
|
|
Viscosity (cP)
(Mean ± SD)
|
2.72 ± 0.89
|
2.45 ± 0.36
|
3.77 ± 0.47
|
2.98 ± 1.03
|
A viscometer, also known as viscosimeter, is an
instrument used to measure the viscosity and flow parameters of a fluid. There
are many types of viscometers in the market and the type that we used in this
experiment is the rotational viscometer. Viscometer operates by means of a
cylinder or spindle that is immersed in a liquid. The cylinder or spindle
undergoes retarding force due to the viscous drag of the liquid. The viscometer
will then measure the additional torque required to maintain a constant speed of
rotating to overcome the flow resistance. The higher the resistance, the higher
the viscosity. The viscometer calculates the result and shows the value of
viscosity in centipoise (cP) or milliPascal-second (mPa·s). 1 cP is equivalent
to 1 mPa·s. A wide range of viscosity can be measured using viscometers with
different types of spindles and speed ranges. Each spindle is categorized by
different letter and number.
In
this experiment, we measured the viscosities of various suspensions. The
suspensions varied in the weight of Tragacanth they contained, from the
suspension without Tragacanth to suspensions containing 0.1 g, 0.3 g and 0.5 g
of Tragacanth. Tragacanth,
a natural polysaccharide, is a suspending agent which thickens the preparation.
Therefore, the higher the weight of Tragacanth, the higher the viscosity of the
suspension. Theoretically, the viscosity of the suspension is
directly proportional to the weight of Tragacanth the suspension contains.
Although we did not get a linear graph which we were supposed to get
theoretically. This may be due to the error occur during the experiment. It was
possible that there was an incomplete mixing of Tragacanth and chalk which
caused the viscosity to be not uniform throughout the suspension. In addition,
we were not sure which spindle size was the suitable one to be used in order to
measure the viscosity of the suspension. The error may be due to the use of
unsuitable spindle size. The viscometer we used also was malfunctioning for a
short period of time before the lab assistant helped us. Thus the viscometer
reading may also be inaccurate or inconsistent. Moreover, the errors can also arise from the improper
cleaning of the spindle from previous use.
5. Plot
a graph of height of ratio of sediment as a result of centrifugation vs. weight
of Tragacanth. Give explanation.
|
|
Height
(mm)
|
|||
|
Group
|
1
|
2
|
3
|
4
|
|
Before centrifuge
|
80
|
80
|
80
|
80
|
|
After centrifuge
|
13
|
12
|
15
|
20
|
|
Ratio of height
|
0.1625
|
0.1500
|
0.1875
|
0.2500
|
|
Tragacanth
composition (g)
|
0.0
|
0.1
|
0.3
|
0.5
|
|
Height
ratio (_ X
± SD)
|
0.1625
|
0.1500
|
0.1875
|
0.2500
|
From the graph we notice that there is a decrease of
ratio of sedimentation from suspension I to II, and then there is an increase
from suspension II to III and from III to IV. Theoretically, a hyperbola graph
should be obtained. Ratio of sediment is influence by weight of Tragacanth.
Ratio of sediment is decreasing slowly with increasing weight of Tragacanth.
Suspension contains more Tragacanth is more stable. Therefore, the more higher
the Tragacanth content, the lower the sediment formed.
Therefore the result of this experiment is not
followed the theoretically result and this may be due to some error during the
experiment or may be the tragacanth used is expired.
6. Plot a graph of height of ratio of sediment as a
result of centrifugation vs. weight of Tragacanth. Give explanation.
|
Amount of
Tragacanth (g)
|
0.0
|
0.1
|
0.3
|
0.5
|
|
Ratio of
height
|
1.67
|
0.36
|
5.64
|
0.11
|
From the graph above,
the ratio of height decreases as the amount of tragacanth increases. According
to theory, the ratio of height of sediment is influenced by the weight of
tragacanth. Ratio of height of sediment decreases slowly with increasing weight
of tragacanth. Suspension that contains more tragacanth is more stable.
Therefore, the higher the Tragacanth content, the lower the sediment formed.
The result of the experiment is not accurate as the results do not shows
exactly a gradual decrease in the ratio of height of sediment when the amount
of tragacanth increases especially the error on experiment 0.3g tragacanth.
This is most probably caused by the error when measuring the amount of
tragacanth. The less amount of tragacanth cause the high height of sediment
formed.
Conclusion
The rate of sedimentation and the height of sediment
formed in the suspension depends on the amount of different Tragacanth powder
used to form the suspension. When the amount of tragacanth powder increases, sedimentation
rate will be more slowly and thus sediment height will be lower.The higher the
amount of Tragacanth powder, the lower the height of sediment formed. This is
due to the action of Tragacanth powder that prevent the solution from forming
sediment.
Conversely,
low amount of tragacanth produces a coarser, more liquefied suspension. Clearer
suspension resulted as solid phase will settle more rapidly. Thus stability of
suspension will decrease. Redispersibility is easier for lower tragacanth
amount.
References
1. Aulton, M.E.2002. Pharmaceutics: The Science of
Dosage Form Design. Edinburgh: Churchill Livingstone.
2. British Pharmaceutical Codex 1973
3.Pharmaceutical Practice, Winfield Richards, 2nd Edition
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