Introduction :
Suspension
is a heterogeneous mixture in which solute-like particles settle out of a
solvent-like phase sometime after their introduction. We apply the word
'suspension' when particles are big enough to eventually settle. In this
experiment, it is a mixture of solid particles in liquid medium. If the
particles are too small to ever settle, they are said to form a colloid. We use the terms 'solute-like' and 'solvent-like,'
because we are dealing with a heterogeneous mixture, while the terms solute and
solvent refer to solutions, which are homogeneous. An example of a suspension is mixture of water and
sand. After we stirred it, the sand and water will moving together but after a
period of time, the sand will suspended at the bottom of the container if leave
undisturbed. As we know, there are 2 types of suspension which are coarse
suspension and colloidal suspension. The diameter of particles in coarse
suspension is more than 1 µm while in colloidal
suspension is less than 1 µm in diameter.
In this experiment, we use
tragacanth as a stabilizer. Dispersed phase (solid-phase) in suspension will
eventually sediment as time passed by. To prevent the sedimentation of the
dispersed phase, we use stabilizer. The importance of stabilizer can be
explained by the usage of the stabilizer in suspension of drug. If a patient
pour out some of the drug while the active ingredient sediment at the bottom of
the container, the dose that the patient receive will be less. Moreover, at the
end of the drug usage, the patient will be overdosed as the all the active
ingredient sediment at the bottom of the container. Tragacanth that we use in
this experiment act as suspending agent. Suspending agents also act
as thickening agents. They increase in viscosity of the solution, which is
necessary to prevent sedimentation of the suspended particles as per Stoke’s
law. A good suspension should
have well developed thixotropy. At rest the solution is sufficient viscous to
prevent sedimentation and thus aggregation or caking of the particles. When
agitation is applied the viscosity is reduced and provide good flow
characteristic from the mouth of bottle. The stability of the suspensions depends on the
types of suspending agents rather than the physical properties of the drugs.
the physical stability of suspension was mainly dependent on the type of
suspending agent rather than the physical characteristics of the drug.
Stability pH range and concentrations of most commonly used suspending agents for suspension
Suspending agents
|
Stability pH range
|
Concentrations used as suspending agent
|
Sodium alginate
|
4-10
|
1-5 %
|
Methylcellulose
|
3-11
|
1-2 %
|
Hydroxyethylcellulose
|
2-12
|
1-2 %
|
Hydroxypropylcellulose
|
6-8
|
1-2 %
|
Hydroxypropylmethylcellulose
|
3-11
|
1-2 %
|
CMC
|
7-9
|
1-2 %
|
Na-CMC
|
5-10
|
0.1-5 %
|
Microcrystalline cellulose
|
1-11
|
0.6-1.5 %
|
Tragacanth
|
4-8
|
1-5 %
|
Xanthangum
|
3-12
|
0.05-0.5 %
|
Bentonite
|
>6
|
0.5-5.0 %
|
Carageenan
|
6-10
|
0.5-1 %
|
Guar gum
|
4-10.5
|
1-5 %
|
Colloidal silicon
dioxide
|
0-7.5
|
2-4 %
|
The aim of the experiment is to study the effect of Tragacanth in a suspension. In this experiment, a formulation of 150 ml Pediatric Chalk Mixture will be formed by using Tragacanth as suspending or thickening agent. For each group, the amount of the Tragacanth that will be used will be different. 50 ml of the suspension will placed in a 50 ml measuring cylinder. As the time passed by, the height of the solid phase formed at the bottom of the cylinder will be measure. Then, the balance of the suspension will be used to measure the viscosity of the suspension using viscometer apparatus. By using the Coulter Counter technique, the amount of particles that more than 25 µm in diameter will be determine. The last part in this experiment is to measure the height of solid phase formed before and after shacked. It is done by using 10 ml of the suspension and placed in shacking device and let it be shacked for 5 minutes.
Apparatus :
Weighing
instrument
Weighing
boat
Mortar
and pestle
150
ml plastic bottle
50
ml measurable cylinder
200
ml measurable cylinder
1
set of 1 ml pipette and pipette bulb
1
centrifugator tube 15 ml
100
ml beaker
Centrifugator
Viscometer
Materials :
Chalk
Tragacanth
Concentrated
Peppermint Water
Syrup
BP
Double-strength
chloroform water
Distilled
water
Procedures
:
1.
Pediatric Chalk Mixture (150mL)
formulation of suspension is prepared by using formula as followed :
Chalk
|
3g
|
Tragacanth
|
0.1g
|
Concentrated peppermint water
|
0.6mL
|
Syrup BP
|
15mL
|
Double-strength Chloroform water
|
75mL
|
Distilled water, q.s.
|
150mL
|
2.
5mL of suspension formed is poured into
a weighing boat and is labeled. The suspension formed is elaborated and
compared its texture, clearance and also color.
3.
50mL of suspension formed then is put
into 50mL of measuring cylinder and the height of sediment solid is measured on
0, 5, 10, 15, 20, 25, 30,40,50, and 60 min.
Time (min)
|
0
|
5
|
10
|
15
|
20
|
25
|
30
|
35
|
40
|
45
|
50
|
55
|
60
|
Height (mm)
|
4.
The remaining suspension (95mL) is
poured into a 100mL beaker and the viscosity is determined by using viscometer.
Reading
|
1
|
2
|
3
|
4
|
5
|
6
|
Viscosity
|
||||||
Mean
+ SD
|
||||||
5. By using the Coulter Counter technique, the amount of the particles that more than 25 µm in diameter was determined.
6. 10 ml of the
suspension was transferred into shacking device and the height of the solid
phase was recorded before and after being shacked.
Results and Discussion :
1) Compare the physical characteristics of the suspension formed and give comments.
1) Compare the physical characteristics of the suspension formed and give comments.
Tragacanth
|
Texture
|
Clarity
|
Colour
|
0.0 (Suspension 1)
|
Smooth (Less viscous)
|
Two layers are form. The above layer is clear
whereas the bottom layer is cloudy.
|
White
|
0.1 (Suspension II)
|
Diluted (Viscous)
|
Cloudy
|
Opaque white
|
0.3 (Suspension III)
|
Smooth, dilute (More viscous but a bit late)
|
Initially milky and not clear. After some time,
cloudy and the suspended matter is visible.
|
White and transparent above the white layer
|
0.5 (Suspension IV)
|
Smooth (More viscous)
|
Cloudy
|
White
|
Based on the
results, the higher amount of tragacanth the more cloudy the suspension is. This
is because the
amount of tragacanth determine the uniformity in the distribution phase of a
suspension. The more amount of tragacanth added, the more uniform the
suspension, the more cloudy it is. When there is no amount of tragacanth added,
that is the Suspension I, the texture is less viscous. The highest amount of
tragacanth added is the Suspension 1V, this is the stage where the most viscous
of suspension can be seen.
There
is an obvious 2 layers in Suspension I, this shows that the suspension is not
uniform in color. The above layer is
clear whereas the bottom layer is cloudy. This is due to the presence of
particles or white powder that are not uniformly dispersed in it.
For
suspension II, the particles spread more uniformly if compared to suspension I,
causing it is to appear moderately cloudy and having a milky colour. This is
because there is small amount of tragacanth added and causing it to disperse
uniformly than the previous Suspension II.
Both
suspensions III and IV were homogenous suspension when compared with suspension
I and II. They are more cloudy and the colour is milky too. All the suspensions
are cloudy and white in colour. This is due to the dispersion of the insoluble
chalk particles in the solution. But
before the Suspension III become more viscous than the Suspension II, it takes
some time to be so. This is because the amount of tragacanth added need some
time to be dispersed uniformly compared to Suspension IV.
2)
Plot
a graph of the height of sediments against time. Give explanation.
TIME (MIN)
|
0
|
5
|
10
|
15
|
20
|
25
|
30
|
35
|
40
|
45
|
50
|
55
|
60
|
HEIGHT OF
SEDIMENTATION (MM)
|
136
|
134
|
133
|
133
|
133
|
133
|
132
|
132
|
132
|
132
|
132
|
132
|
132
|
The graph above shows that the height
of sedimentation of a suspension, which is formulated with 0.5 g of tragacanth
powder against time. According to this graph, the suspension does not contain
any sediment at the beginning of the experiment. As the time passes,
sedimentation will start to form. It can be seen that there is a continuous
gradual decrease from the beginning until the 10th minute . It
become constant after 10 minutes. From
25th minute until 30th minute, the height of
sedimentation continually decreases again. After 30 minutes, it remained
constant until the end. This is due to the presence of tragacanth, which is
known as suspending agent that causes the contents to settle gradually.
Tragacanth forms film around particle and decreases the interparticle
attraction resulting in lower sedimentation rate. The height of sedimentation
will decrease over time until maximum sedimentation level is achieved. On the
other words, as the time increases, the line of the graph starts to become
constant which shows that mostly all the particles have been sedimented. Based
on the graph, the maximum sedimentation level starts from 30th
minute till 60th minute.
3) Plot a graph of height of sediment
vs. time for the formulation of suspension that contain varied amount of
Tragacanth. Give explanation.
Time
(min)
|
Average
height of sedimentation (mm) ( X ± SD)
|
|||||||||||||
0
|
5
|
10
|
15
|
20
|
25
|
30
|
35
|
40
|
45
|
50
|
55
|
60
|
||
Amount
of tragacanth (g)
|
0.0
|
0
|
20
|
50
|
50
|
60
|
60
|
70
|
70
|
80
|
80
|
80
|
80
|
80
|
0.1
|
140
|
140
|
110
|
90
|
90
|
90
|
90
|
90
|
90
|
80
|
80
|
80
|
80
|
|
0.3
|
121
|
121
|
121
|
120
|
120
|
119
|
119
|
119
|
119
|
119
|
119
|
119
|
119
|
|
0.5
|
136
|
134
|
133
|
133
|
133
|
133
|
132
|
132
|
132
|
132
|
132
|
132
|
132
|
|
Height of
sedimentation vs. Time for Different Tragacanth Content
The graph above shows
that height of sedimentation increases from the beginning until 40th
minute for 0.0 g of tragacanth powder, followed by a constant level of height
as the time passes. This is due to the absence of tragacanth powder because the
particles tend to regroup, to flocculate, and they are held by van der Waals
forces. Theoretically, the height of sedimentation should decrease over time
because the stronger forces are involved.however, this is may be due to the
small changes occurs in height of sedimentation that is difficult to be
identified and measured.
As the amount of
tragacanth powder increases, the height of sedimentation decreases over time.
This is because the presence of tragacanth powder in suspension will make the
suspension to become more stable. The greater the amount of tragacanth powder,
the longer the time taken for the sediment to form. Tragacanth powder, which is
a suspending agent, able to suspend the particles in the suspension which
counteract the gravity force. Thus, the stable suspension is formed. Other than
that, the particles are filled in the spaces between the porous structures to
make the sediment become more compact. The sediment forms a cake at the bottom
of the measuring cylinder. In compacted cake, stronger forces are involved. The
tragacanth powder in suspension are able to
coat the solid hydrophobic particles with a multimolecular layer, which will
impart the hydrophilic character to the solid and promote wetting effect. It
also reduces the sedimentation by structuring the continuous phase to produce a
deflocculated system.
4) Describe briefly the mechanism of analysis of
viscometer. Plot a graph of viscosity versus weight of Tragacanth (g). Give
explanation.
Formula of standard
deviation (SD):
Where n=6
Suspension I (0.0g
Tragacanth):
Group 1
Reading
|
1
|
2
|
3
|
4
|
5
|
6
|
Viscosity (cP)
|
2.50
|
3.60
|
3.40
|
2.20
|
2.10
|
4.40
|
Average + SD
|
3.03±0.83
|
|||||
Suspension II (0.1g
Tragacanth):
Group 3
Reading
|
1
|
2
|
3
|
4
|
5
|
6
|
Viscosity (cP)
|
5.00
|
3.00
|
4.00
|
5.00
|
5.00
|
4.00
|
Average + SD
|
4.33±0.75
|
|||||
Suspension III (0.3g
Tragacanth):
Group 5
Reading
|
1
|
2
|
3
|
4
|
5
|
6
|
Viscosity (cP)
|
2.80
|
2.90
|
2.10
|
2.70
|
2.20
|
2.20
|
Average + SD
|
2.48±0.32
|
|||||
Suspension IV (0.5g
Tragacanth):
Group 7
Reading
|
1
|
2
|
3
|
4
|
5
|
6
|
Viscosity (cP)
|
3.00
|
4.70
|
5.90
|
4.00
|
5.90
|
5.90
|
Average + SD
|
4.90 ± 1.12
|
|||||
Overall :
Amount of Tragacanth (g)
|
0.0
|
0.1
|
0.3
|
0.5
|
3.03±0.83
|
4.33±0.75
|
2.48±0.32
|
4.90 ± 1.12
|
Viscosity vs.
Tragacanth Content
The device used is called the viscometer. It is an
instrument used to measure the viscosity and flow parameters of a fluid. The
type that we used in this experiment is the rotational viscometer. This device measures fluid viscosity at fixed
rotation speeds by driving a measurement tool (spindle), immersed in the test
fluid, through a calibrated torsion spring. Viscous drag of the fluid against the spindle causes
the spring to deflect, and this deflection is correlated with torque. The
calculated shear rate depends on the rotation speed, the tool
geometry, and the size and shape of the sample container. Conversion factors
are needed to calculate viscosity from the measured torque, and are typically
pre-calibrated for specific tool and container geometries. For Newtonian fluids the torque is proportional to the
product of viscosity and rotational speed, but this proportionality is lost in
the case of a non-Newtonian fluid.
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
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. However, we did not get the linear graph as
we should get. The theoretical graph should be an increase of weight of
tragacanth increases the viscosity of the suspension. This is due to some errors that might be occurred during the
experiment. There might be an incomplete mixing of tragacanth and chalk. This
causes the result obtained to be affected and not uniform.
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
|
Group 3
|
Group 5
|
Group 7
|
|
Before centrifuge
|
85
|
80
|
82
|
82
|
After centrifuged
|
15
|
65
|
20
|
21
|
Height separation ratio
|
0.176
|
0.813
|
0.244
|
0.256
|
Amount of tragacanth (g)
|
0.0
|
0.1
|
0.3
|
0.5
|
height separation ratio
|
0.176
|
0.813
|
0.244
|
0.256
|
Ratio Height
Separation after Centrifuge vs. Tragacanth Content
Based
on the graph, the ratio of height is not linear. This is due to some errors
that had occurred while carrying out the experiment. The Suspension II
(tragacanth = 0.1 g) might be the reason why. This is because the error while
mixing to form the suspension.
The actual result should be, 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 considered accurate as the results shows a gradual decrease
in the ratio of height of sediment when the amount of tragacanth increases.
6) What
is the function of each material that is used in the suspension formulation?
How is the use of different amount of Tragacanth affect the physical
characteristic and stability of a suspension formulation?
Material
|
Function
|
Chalk
|
- an adsorbent and antacid
-As active ingredient (used in the treatment of
diarrhea)
|
Tragacanth
|
-act as suspending agent and thickening agent. They
reduce the cohesion between solid and liquid particles of aqueous medium. They
also increase in viscosity of the solution, which is necessary to prevent
sedimentation of the suspended particles. Higher amount of tragacanth will
produce a smoother suspension. Suspension containing tragacanth is more
stable but it is hard to redisperse on prolonged storage. Suspension without
tragacanth has low stability which will form sedimentation rapidly but it is
easy to redisperse.
|
Concentrated Peppermint Water
|
-As flovouring and perfuming agents which increase
the patient acceptance and are capable of masking the unpleasant taste. It
also give carminative effect for the suppositories.
|
Syrup BP
|
-as diluent
-As sweetening agent and cosolvent by preventing
crystallization and maintaining solubility of all ingredients. It also
increases the viscosity of the suspension and mask the unpleasant taste so
that compliance of the patient is increased.
|
Double-strength Chloroform Water
|
-Preservative and sweetening agent (prevent
microbial growth). They should posses a broad spectrum of antimicrobial
activity encompassing Gram-positive and Gram-negative bacteria and fungi.
They also should be chemically and physically stable over the shelf life of
the product and have low toxicity. If the suspension is not preserved
properly, then an increase in microbial activity may cause stability problem
suc as loss in suspending activity of suspending agents, loss of colour,
flavor and odour, change in elegance, and others. Antimicrobial activity is
potentiated at lower pH.
|
Distilled Water
|
-Act as vehicle (to carry all the active ingredients
in the pharmaceutical suspensions into patient’s bodies)
-As diluents (to give aqueous medium). It also
lessen the therapeutic effect of the drug preparation and prevent the
imbalance and inaccurate dosing.
|
Conclusion
:
Tragacanth
act as a suspending and thickening agent. Suspension with higher amount of
tragacanth used will have a smoother texture since tragacanth causes the insoluble
chalk particles to disperse evenly throughout the continuous phase. This also
causes the suspension colour to be more milky white. Larger amount of tragacanth
makes the suspension more stable and thus solid particles is dispersed for a
longer time which render the suspension to be more cloudy. Suspension without
tragacanth has higher clarity since it sediment faster, forming a clear layer
on top of the sediment. Weight of tragacanth used influences the viscosity of
the suspension because it thickens the preparation. Although the results
obtained is less accurate, theoretically the weight of tragacanth contained in
a formulation is directly proportional to the viscosity. Based on the result, height
of sediment decreases over the time for all formulation of different weight of
tragacanth. There maybe a misinterpretation of the definition or less visible
sediment formed. Theoretically suspension with lower amount of tragacanth
should have a rapid increase in height of sediment as the preparation is not
stable. On the other hand, formulation with higher amount of suspending agent
will have a gradually increase readings. When the suspension is stable and the
dispersion of dispersed phase is uniform, hence the time taken for it to
sediment would be longer. After centrifugation, the ratio of height of sediment
decreases with increasing amount of tragacanth in formulation. This is because
of the stability provided by the suspending agent tragacanth.
Appendix:
( All the apparatus and materials that needed to produce the suspension )
( The suspension is poured into the measuring cylinder to observe the sedimentation process )
( The height of sedimentation is observed and measured by using a ruler )
( The materials chalk and tragacanth are mixed by using mortar and pestle )
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