3) The viscosity of the emulsion;
Group (mL)
|
before heat cycle
|
SD (sebelum')
|
after heat cycle
|
SD (selepas)
|
Viscosity difference(%)
|
1 (20)
|
90
|
10
|
96.67
|
5.77
|
7.41
|
2 (25)
|
409.9
|
17.32
|
739.83
|
69.22
|
80.4
|
3 (30)
|
219.96
|
17.26
|
459.9
|
75.49
|
109.1
|
4 (35)
|
633.33
|
28.87
|
300
|
0
|
52.6
|
5 (20)
|
110
|
10
|
136.67
|
5.77
|
24.2
|
6 (25)
|
409.9
|
17.32
|
810.9
|
68.82
|
97.8
|
7 (30)
|
53.33
|
5.77
|
50
|
0
|
6.24
|
8 (35)
|
826.67
|
90.18
|
926.67
|
30.55
|
12.1
|
The viscosity difference of the emulsion;
Our formulation should be the same as Group 8. However,
incorrect techniques makes us unable to form a good emulsion. Same as other
groups, we also use the wet gum method and we make mistake at the mixing
process which is the initial step. The acacia gum added to the mortar and mixed
it slowly with water by using the pestle until a smooth qum is formed. Overmixing
can generate heat and may denature or rupture the nature structure of the
emulsifying agent which is the acacia gum. The smooth gum is mixed vigorously
only after the oil is triturated in portions.
Without the stabilising effect of emulsifying agent, the
cohesive forces become more favourable than the adhesive forces, hence the
interfacial tension increases, and the oil globules tends to coalesce in order
to reduce the surface free energy which is thermodynamically favourable.
Eventually, there will a separation into different phases and breaking process
of the emulsion will happen. That is why the viscosity of our emulsion is lower
compared to Group 8 before the heat cycle process is carried out.
As the lab is about to close during that evening, our
emulsion also have to be stored about 24 hours before the next heat cycle
process. This will extent the rate of phase separation and the breaking process. As a result, the viscosity of the emulsion become
lower after the heat cycle process.
4. Plot graph of separated phase ratio formed
from the centrifugation process versus the different volume of oil.
The table and graph above show the ratio of separation phase, the
average value and their standard deviation to indicate the stability of the emulsion.
Basically, a good emulsion must be stable enough to not undergo coalescence,
phase separation and reverse phase. Otherwise, the formulation will cause a
lots of problems including the inaccurate dose to the patients resulting in
overdose or underdose which can exacerbate the patient conditions.
Generally, an emulsion with a
high ratio of separation phase is not stable , on the contrary, the emulsion
with the lowest ratio of separation phase is the most stable. In this
experiment, 25 ml of Arachis oil mix
with 6.25g of acacia and other
excipients show the highest ratio of
phase separation followed by 30 ml of olive oil,20ml of palm oil and 35ml of
the mineral oil. Theoretically, the separation phase ratio should be increasing
with the increasing of the mineral oil contain in the formulation.
The date obtained from the experiment
maybe inaccurate due to some error in the process in which the experiment is
carried out. The different types of oils being used in the experiment is one of
the main reason for the inaccurate data. Different types of oil needs different
amount of acacia to obtain a good emulsion. Besides, This may due to the
homogenous process was not done properly. Inaccurate measurement of the highly
viscous surfactant that is to be added into the formulation is also one of the
reasons. In addition, the height of the separated phase might not be measure
accurately too.
5. What is the
function of each ingredient used in the emulsion preparation? How can the
different amount of ingredients influence the physical characteristics and the
stability of the emulsion?
- Mineral oil – the
oily phase in the o/w emulsion
- Acacia –
emulsifying agent which reduces the interfacial tension and maintain the
separation of the droplets in the dispersed phase.
- Syrup – as the
sweetening agent and increase the viscosity of the emulsion
- Vanillin – as the
flavoring agent
- Alcohol – as the
antimicrobial agent
- Distilled water –
as the aqueous phase in the o/w emulsion
Amount of the mineral
oil (oily phase) and the distilled water (aqueous phase) used is important to
determine the type of emulsion formed, whether o/w or w/o emulsion. The volume
of the dispersed phase should not be more than the volume of the continuous
phase. Or else, phase inversion will occur.
Acacia which acts as
the emulsifying agent should be used in appropriate amount according to the HLB
value. If the amount used is less than which is required, the emulsion formed
is not uniform due to the large interfacial tension between the dispersed phase
and the continuous phase. Then the separation of phase will occur.
Syrup will affect the
viscosity of the emulsion formed as it is a viscous liquid. Suitable amount of
syrup should be used to give suitable viscosity to the emulsion formed.
Viscosity of the emulsion will affect the physical stability and the
rheological characteristic of the emulsion. Alcohol which acts as the
antimicrobial agent should not be used in large amount to reduce toxicity.
Conclusion
The HLB value of the surfactant used will affect the stability of the
emulsion formed. The higher the amount of oily phase used in the emulsion, the
emulsion formed will be more unstable. Homogenization causes the reduction in
size of the globules in the emulsion and the emulsion formed is more homogenous
and smooth.
Reference
Aulton, M.E. Pharmaceutics: The
science of dosage form design. Edinburgh: Churchill Livingstone.
Appendices
Our emulsion after being centrifuged :
Our emulsion after the heat cycle process:
Our emulsion before (B) and after (A) the homogenization process:
video how to prepare emulsion :
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