EXPERIMENT
3: EMULSION
Title: The effects of different kinds of substances on the properties of a formulation of emulsion.
Objectives:
- To determine the effect of HLB surfactant on the emulsion stability
- To find out the physical effects and stability on emulsion formulation due to the different kinds of emulsifying agents used in the experiment.
Introduction:
Emulsion is the two phases
system that instable on thermodynamic. It contains at least two immiscible
solutions. Emulsion is usually refers to as: oil in water (O/W) when the
droplet is air and water is the external phase. Water in oil (W/O) when the
droplet is water and oil is the external phase. Adding the emulsifying agents
stabilizes emulsion. They are hydrophilic colloids, active surface agents or
surfactants.
One method, HLB method (hydrophilic-lipophilic
balance) used to determine the quantity and the types of surfactant that needed
to prepared a stable emulsion. Every surfactant, have one number in HLB scale
from 1 (lipophilic) to 20 (hydrophilic). Usually the combination of the two
surfactants agents is used to produce the more stable emulsion. The HLB value
for the combination of the emulsifying agents can be determined using the
formula below:
HLB value: (quantity of surfactant 1)(HLB) surfactant 1)(quantity
surfactant 2)(HLB surfactant 2)
quantity surfactant 1 + quantity
surfactant 2
Apparatus:
8
test tube 1
set 5ml pipette and bulb
1,
50ml measuring cylinder 1,
50ml beaker
2
set pipette and droppers 1,
15ml of centrifuged tube
Vortex coulter counter
Weighing
boat centrifuge
1
set mortar and pestle viscometer
Light
microscope water
bath (450C)
Microscope
slide refrigerator
(40C)
Materials:
Coconut
oil distilled
water
Arachis
oil span
20
Olive
oil tween
80
Mineral
oil Sudan
III solution (0.5%)
ISOTON
solution III
Procedure:
1. The
test tubes are labelled and one straight line is draw from the bottom of the
test tube.
2. 4ml of
oil and 4ml of distilled water are mixed in the test tube.
3. In the
mixture of oil and water, span 20 and tween 80 are dropped. The test tubes are
closed and the vortex is mixed into the test tube for 45 seconds. The time
taken needed for the interface to reach 1 cm line is recorded. The HLB value is
determined for each sample.
4. The several
drops of Sudan III solution are dropped into 1 g of emulsion in the weighing
boat. The sample is put onto the microscope slide and the sample is observed
under the light microscope. The shape and size of the globules formed is draw,
described and compare between each other.
5. The
formulation of mineral oil emulsion (50g) is prepared using wet gum method.
Mineral oil
|
Refer table III
|
Acacia
|
6.25g
|
Syrup
|
5ml
|
Vanillin
|
2g
|
Alcohol
|
3ml
|
Distilled water, qs
|
50ml
|
6. 40g of
the emulsion formed is put into 50ml beaker and the process of homogenous is
carried out for 2 minutes.
7. The 2g
of the emulsion formed is taken (before and after homogenous) and put into the
weighing boat and label. The Sudan III solution is dropped into the emulsion
and spread it out. The texture, consistency, the degree of oily and spreading
color is described and compare under the light microscope.
8. The
viscosity of the emulsion (15g in 50ml of beaker) that formed is determined
after homogenous using viscometer. The sample is let to expose to 450C
(water bath) for 30 minutes and then the temperature of 4 0C
(refrigerator) for 30 minutes. The viscosity is determined after the exposure
to the temperature is done and the emulsion reached the room temperature.
(10-15 minutes).
9. 5g of
homogenous emulsion is pun into the centrifuged tube and centrifuged (4500rpm,
10 minutes, 250C). The separating height formed is measured and the
separating ratio is determined.
Results and discussion:
1.
What
are the values of HLB that will yield a stable emulsion? Discuss.
HLB system prredicts how oils and surfactants will likely interact.Smaller or greater HLB respectively can yield a stable emulsion.An optimum hydrophilic chain length of surfactant is required to obtain stable emulsion for particular oils and temperature.The required HLB are accurate to +/- 0.5 HLB units.
HLB system prredicts how oils and surfactants will likely interact.Smaller or greater HLB respectively can yield a stable emulsion.An optimum hydrophilic chain length of surfactant is required to obtain stable emulsion for particular oils and temperature.The required HLB are accurate to +/- 0.5 HLB units.
s
2. Compare
the physical appearance of the mineral oil emulsions produced and give your
comments. What is Sudan III test? Compare the colour dispersion in the
emulsions produced
and give your comments.
3. Plot and discuss:
and give your comments.
Sudan
III/IV test is used to detect the hydrocarbon chains of lipids. Sudan is a red, non-polar, dye that forms
hydrophobic interactions with the hydrocarbon chains of lipids. Alternatively, the Brown Bag test can also be
used to identify lipids due to the oily nature of hydrocarbon chains.
Fats
are hydrophobic organic molecules that are rich in energy due to their high
density of C-H bonds. They can be detected by the Sudan Test, which relies on
hydrophobic interactions between Sudan III dye and lipids. Sudan III dissolved
in ethanol is allowed to interact with the lipids bound to a filter, then when
the filter is washed with water the water will not permit Sudan III bound to
the lipids to escape. Consequently, spots containing lipids will appear orange
against a pink background.
3. Plot and discuss:
Volume of
mineral oil (ml)
|
Average of viscosity (cP)
|
Difference viscosity (%)
(mean ± SD)
|
|
Before
temperature cycle
|
After
temperature
cycle
|
||
20
|
12.67
|
36 |
95.87 %
|
25
|
498.67
|
86.67 |
140.77 %
|
30
|
161.67
|
413.33
|
87.53 %
|
a 4. Graph
of sample viscosity before and after the temperature cycle vs. the content of
mineral oil.
From the graph above, the viscosity of emulsion before temperature cycle
increases as the amount of mineral oil increases. The increasing proportion of mineral oil
also indicates the increasing amount of acacia as emulsifying agent from the
ratio of 4:2:1. The ratio indicates 4 parts of oil, 2 parts of water and 1 part
of acacia. The increase amount of acacia will reduce the surface tension and
increases the viscosity of the emulsion, so that the emulsion will not easily
separate into two layers. However for
mineral oil with 30 ml, the graph is decreasing. This may cause by the errors
during the experiment or during the manufacturing process of emulsion.
b.
Graph
of difference viscosity (%) vs. amount of oil (mL)
Based
on the graph above, the percentage
difference of viscosity (%) increases with increasing amount of mineral oil
used. But there are slightly decrease of percentage difference of viscosity (%)
when using 25 mL of mineral oil. All type of emulsion is exposed to the same
temperature. The emulsions all have the same volume, but different proportion
of oil, water and emulsifying agent proportions. The percentage difference
indicates the difference between the viscosity before and after the temperature
cycle. For 20 mL of mineral oil used, the percentage difference of viscosity is
95.87 %. The difference shows that it is
a bit viscous. For 25 mL of mineral oil used, the percentage
difference of viscosity is 140.77 %, which is higher than mineral oil of 20 mL.
For 30 mL of mineral oil used, the percentage difference is 87.53 %, which is
lower than 25 mL of mineral oil used. This may be due to some errors
that occur during the experiment because the percentage difference should be
higher than 25 mL of mineral oil used. The
percentage difference of viscosity (%) should increase with increasing amount
of mineral oil used. This is because increase amount of mineral oil used
indicates the increasing amount of emulsifying agent, thus increases the
viscosity of the emulsion. Due to temperature cycle, increasing amount of
mineral oil used will cause some loss of water. Then, it will form water-in-oil
emulsion. The emulsifying agent becomes less soluble in the continuous phase, so
it reduces the viscosity of emulsion after the temperature cycle. This will
cause the difference of viscosity before and after the temperature cycle
becomes larger. Thus the percentage difference of viscosity (%) will increases
with increasing amount of mineral oil.
4.
Plot graph of separated phase ratio formed from the
centrifugation process versus the different amount of oil. Discuss.
Volume of
Mineral oil (ml)
|
Phase
separation (mm)
|
Initial
emulsion
(mm)
|
Separation
phase ratio
|
Average
separation phase ratio
(x ± SD)
|
20
|
32
|
49
|
0.6531
|
0.6535±0.00049
|
34
|
52
|
0.6538
|
||
25
|
36
|
54
|
0.6667
|
0.6636±0.0044
|
35
|
53
|
0.6604
|
||
30
|
38
|
55
|
0.6909
|
0.6881±0.0040
|
37
|
54
|
0.6852
|
Based on graph above, increase
in amount of mineral oil in an emulsion, will increase the phase separation
ratio. The mineral oil will separate after 10 minutes homogenous process with
4500 rpm and 25˚C.
5.
What
are the roles of each ingredients used in this emulsion formulation? How does
it affect the physical and stability in the formulation?
· Mineral oil: one
of the classes of oil used to produce water-in-oil emulsion
· Tween 80 & Span 20 : As
emulsifying agents used to emulsify two immiscible liquid which are liquid and
oil into a miscible form called emulsion. The hydrophobic tails will be in contact
with the oily phase while the hydrophilic head group will be in contact with
the aqueous phase. This lowers the surface tension of water molecule and
provides an evenly mixing between oil and water molecule. This makes the
emulsion more stable.
· Acacia Gum: Act
as emulsifying agent, stabilizer, adhesive, flavor fixative and inhibitor of
sugar crystallization. It also ensures that the oil phase is finely dispersed
throughout the water.
· Syrup: to mask the unpleasant
taste of the mineral oil and increase patient compliance as it contains a high
concentration of sugar. It can also be used to increase the viscosity of the
emulsion.
· Vanillin: Act as flavoring agent,
which can increase the taste of emulsion, therefore may help on increasing the
patient compliance as an emulsion always contains a taste not preferred by most
of the patients.
· Alcohol: As a preservative in
this oil-in-water emulsion, as emulsion contains a high proportion of water
present so it is very susceptible to microbial contamination.
· Distilled Water:
aqueous phase (continuous phase) in oil-in-water emulsion.
Conclusion:
Combination of surfactants will give
the accurate HLB value required to form a stable emulsion. Different types of
oil have different viscosity. The higher the amount of oil, the higher the
viscosity and the more the separation phase.
References:
1. Collett,
D.M. & Aulton, M.E. 1990. Pharmaceutical practice. Ed. ke-3. Edinburgh:
Churchill Livingstone.
2.
Aulton,
M.E. 1998. Pharmaceutics: The science of dosage form design.
3.
British
Pharmaceutical Codex 1973.
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