Introduction
Emulsion is a fine dispersion of minute
droplets of one liquid in another in which it is not soluble or miscible. It is
also a two-phase system that is not stable
thermodynamically. It contains at least two immiscible liquids where one of
them is dispersed homogenously in another liquid. In general, emulsion can be
categorized into 2 types, oil-in-water (O/W) and water-in-oil (W/O). Emulsion
is stabilized by adding emulsifying agent. The HLB method
(hydrophilic-lipophilic balance) is used to determine the quantity and type of
surfactant that is needed to prepare a stable emulsion. Every surfactant is
given a number in the HLB scale, that is, from 1 (lipophilic) to 20
(hydrophilic). Usually a combination of 2 emulsifying agent is used to form a more
stable emulsion. HLB value for a combination of emulsifying agents can be
determined by using the following formula:
HLB value = (quantity surfactant 1)(HLB surfactant
1)+(quantity surfactant 2)(HLB surfactant 2)
Quantity surfactant 1 +
Quantity surfactant 2
Objective
To determine:
1.
The effects of HLB surfactant on the
stability of the emulsion
2.
The effects of different oil phase used
in the formulation on the physical characteristics and stability of the
emulsion
Procedures
1.
Each test tube is labelled and 1cm is
marked from the base of the test tube.
2.
4ml of oil (according to table 1) and
4ml of distilled water is mixed into the test tube.
Table
1
Group
|
Oil
|
1,5
|
Palm oil
|
2,6
|
Arachis oil
|
3,7
|
Olive oil
|
4,8
|
Mineral oil
|
3.
Span 20 and Tween 80 is added into the
mixture of oil and water (refer Table 2). The test tube is closed and its
content is mixed with vortex mixer for 45 seconds. The time needed for the
interface to reach 1cm is recorded. The HLB value for each sample is
determined. Step 1-3 are repeated in order to obtain an average HLB value of a
duplicate.
Table
2
Tube no.
|
1
|
2
|
3
|
4
|
5
|
6
|
7
|
8
|
Span 20 (drops)
|
15
|
12
|
12
|
6
|
6
|
3
|
0
|
0
|
Tween 80 (drops)
|
3
|
6
|
9
|
9
|
15
|
18
|
15
|
0
|
4.
A few drops of Sudan III solution is
added to (1g) emulsion formed in a weighing boat and mixed homogeneously. The
spread of the colour in the sample is compared. Some of the sample is spreaded
on a microscope slide and observed under light microscope. The appearance and
globule size formed is drew and described.
5.
A Mineral Oil Emulsion (50g) is prepared
from the formulation below by using wet gum method according to Table 3a
&3b.
Table
3a
Mineral Oil
|
(refer Table 3b)
|
Acacia
|
6.25 g
|
Syrup
|
5 ml
|
Vanillin
|
2 g
|
Alcohol
|
3 ml
|
Distilled water qs
|
50 ml
|
Table
3b
Emulsion
|
Group
|
Mineral Oil (ml)
|
I
|
1,5
|
20
|
II
|
2,6
|
25
|
III
|
3,7
|
30
|
IV
|
4,8
|
35
|
6.
40g of emulsion is placed into a 50ml
beaker and homogenized for 2 minutes using a vortex mixer.
7.
2g of emulsion (before and after
homogenization) are took and placed into a weighing boat and labelled. A few
drops of Sudan III solution is added and mixed. The texture, consistency,
degree of oily appearance and the spreading of colour in the sample under the
light microscope are stated and compared.
8.
The viscosity of the emulsion formed
after homogenization (15g in 50ml beaker) is determined using a viscometer that
is calibrated with “Spindle” type LV-4. The sample is exposed to 45 ºC (water
bath) for 15 minutes and then to 4 ºC (refrigerator) for another 15 minutes.
After the exposure to the temperature cycle is finished and the emulsion had
reached room temperature (10-15 minutes), the viscosity of the emulsion is
determined. Step 8 is repeated again and an average value is obtained.
Table
4
Readings
|
Viscosity(cP)
|
Average
|
|||||
1
|
2
|
3
|
4
|
5
|
6
|
||
Before Temperature cycle
|
|||||||
After Temperature cycle
|
|||||||
Difference (%)
|
9.
5g of homogenized emulsion is placed
into a centrifugation tube and centrifuged (4500 rpm, 10 minutes, 25 ºC). The
height of the separation formed is measured and the ratio of the height
separation is determined.
Table
5
Mineral Oil (ml)
|
Ratio of
|
separation
|
phase
|
Average
|
Ratio of separation phase
|
|
20
|
||||||
25
|
||||||
30
|
||||||
35
|
Apparatus
1.
Test tubes
2.
Measuring cylinder
3.
Pasture pipettes and droppers
4.
Vortex mixer
5.
Weighing boat
6.
Mortar and pestle
7.
Light microscope
8.
Microscope slides
9.
Pipette and bulb
10.
Beaker
11.
Centrifugation tube
12.
Viscometer
13.
Water bath
14.
Refrigerator
15.
Centrifugation apparatus
Materials
1.
Palm oil
2.
Arachis oil
3.
Olive oil
4.
Mineral oil
5.
Distilled water
6.
Span 20
7.
Tween 80
8.
Sudan solution
Result ( Part 1 )
HYDROPHILIC-LIPOPHILIC
BALANCE (HLB) VALUE:
Span
20: 8.6,
Tween
80: 15.0
HLB value = (quantity surfactant 1)(HLB surfactant
1)+(quantity surfactant 2)(HLB surfactant 2)
Quantity surfactant 1 +
Quantity surfactant 2
For palm oil,
Tube No.
|
1
|
2
|
3
|
4
|
5
|
6
|
7
|
8
|
Span 20 (drops)
|
15
|
12
|
12
|
6
|
6
|
3
|
0
|
0
|
Tween 80 (drops)
|
3
|
6
|
9
|
9
|
15
|
18
|
15
|
0
|
Time taken for phase
separation (minutes)
|
41:50
|
37:20
|
33:20
|
27:06
|
26:01
|
25:24
|
3:55
|
1:17
|
HLB value
|
9.67
|
10.70
|
11.34
|
12.44
|
13.17
|
14.05
|
15.00
|
-
|
Spread
of
the colour |
Spread
very slowly
|
Spread
very slowly
|
Spread
slowly
|
Spread
slowly
|
Spread
slowly
|
Spread
moderately
|
Spread
slowly
|
Spread
immediately
|
Tube
No.
|
Observation
under microscope
|
1
 |
-
Various
sizes of A globules were unevenly distributed.
-
Irregular
shape formed
|
2
 |
-
Various
sizes of globules were formed.
-
The
distance between the globule sizes was further.
-
Various
shape formed
|
3
 |
-Not uniform size distribution
but smaller globule sizes can be observed.
- Most
of the globules are in circular shape.
|
4
 |
- Globules are not well
distributed but more small globule sizes can be observed.
- Most
of the globule sizes are in circular size.
|
5
 |
-
The
globules are further separated.
-
All
the globules are in circular shape but in various sizes formed.
|
6
 |
- The globule sizes were in
more uniform sizes and the distribution was more uniform.
- All
the globules are in circular shape.
|
7
 |
- Large globules were observed
but most are in uniform sizes.
- The
globules are not well distibuted
|
8
 |
-
Only
a few globules were formed.
-
Irregular
shapes are formed.
-
Dispersion
of 2 mediums did not occurs.
-
Due
to the absent of emulsifying agent, there was less formation of globules.
-
|
For olive oil:
Tube
No.
|
1
|
2
|
3
|
4
|
5
|
6
|
7
|
8
|
Span
20 (drops)
|
15
|
12
|
12
|
6
|
6
|
3
|
0
|
0
|
Tween
80 ( drops)
|
3
|
6
|
9
|
9
|
15
|
18
|
15
|
0
|
Time
taken for phase separation( minutes)
|
-
|
-
|
57.54
|
11.40
|
32.24
|
14.43
|
37.49
|
16.5seconds
|
HLB
value
|
9.67
|
10.70
|
11.34
|
12.44
|
13.17
|
14.09
|
15.00
|
-
|
Spread
of the colour
|
Spread
very slowly
|
Spread
very slowly
|
Spread
slowly
|
Spread
slowly
|
Spread
moderately
|
Spread
moderately
|
Spread
slowly
|
Spread
immediately
|
Magnification
(4 x 10)
|
Obseervation
under light microscope
|
 |
The
red spherical droplets packed very closely and there were some small and
large size of globule. The emulsion is well dispersed.
|
 |
The
red spherical droplets packed closely as well and almost same amount of small
and large globule was formed. The emulsion is well dispersed.
|
 |
The
red spherical droplets were distributed widely and the globule size was
large, small and irregular.
|
 |
The
red spherical droplets were closely packed, wide spread in the emulsion and
the globule size was regular and small.
|
 |
The
red spherical droplets are well distributed. There are small and large
globules formed in the emulsion.
|
 |
The
spherical globules were distributed. A few of large globules are formed in
the emulsion but mostly are small globules.
|
 |
The
spherical droplets were distributed evenly and there were low portion of
small size globules and high portion of large size globules.
|
 |
The
droplets were not well distributed in the emulsion. The size was quite large
but also contained pretty small size globule.
|
Mineral
oil:
Tube
no.
|
Span
20 (drops)
|
Tween
80 (drops)
|
HLB
value
|
Time
for phase separation (min)
|
||
T1
|
T2
|
Average
|
||||
1
|
15
|
3
|
9.67
|
Interphase did not reach 1cm after 120
minutes
|
Interphase did not reach 1cm after 120
minutes
|
-
|
2
|
12
|
6
|
10.73
|
Interphase did not reach 1cm after 120
minutes
|
Interphase did not reach 1cm after 120
minutes
|
-
|
3
|
12
|
9
|
11.34
|
70
|
69
|
69.5
|
4
|
6
|
9
|
12.44
|
63
|
60
|
61.5
|
5
|
6
|
15
|
13.17
|
55
|
57
|
56
|
6
|
3
|
18
|
14.09
|
45
|
47
|
46
|
7
|
0
|
15
|
15.00
|
12
|
16
|
14
|
8
|
0
|
0
|
0.00
|
0.08
|
0.05
|
0.065
|
Tube
No.
|
Observation
under microscope
|
1
 |
-
Various
sizes of A globules were unevenly distributed.
|
2
 |
-
Various
sizes of globules were unevenly distributed.
-
The
distance between the globule size was further.
|
3
 |
- An uniform distribution and smaller globule
sizes can be observed.
- All
the globules are in circular shape.
|
4
 |
- A
more uniform distribution and smaller globule sizes can be observed.
- Most
of the globule sizes are in circular size.
|
5
 |
-
An
uniform distribution was observed and the globules are in larger size.
-
All the globules are in
circular shape.
|
6
 |
- The globule sizes were in
various sizes and the distribution was less uniform.
- All
the globules are in circular shape.
|
7
 |
- Large globules were observed.
|
8
|
-
Only
a few globules were formed.
-
Dispersion
of 2 mediums did not occurs.
-
Due
to the absent of emulsifying agent, there was no formation of emulsion.
-
|
Arachis
oil:
Tube
no.
|
Span
20 (drops)
|
Tween
80 (drops)
|
HLB
value
|
Time
for phase separation (min)
|
||
T1
|
T2
|
Average
|
||||
1
|
15
|
3
|
9.67
|
95
|
-
|
95
|
2
|
12
|
6
|
10.73
|
94
|
-
|
94
|
3
|
12
|
9
|
11.34
|
93
|
-
|
93
|
4
|
6
|
9
|
12.44
|
42
|
-
|
42
|
5
|
6
|
15
|
13.17
|
31
|
-
|
31
|
6
|
3
|
18
|
14.09
|
61
|
-
|
61
|
7
|
0
|
15
|
15.00
|
8
|
-
|
8
|
8
|
0
|
0
|
0.00
|
1
|
-
|
1
|
Discussion
For
the first part of the experiment, it clearly shows the phase separation of the
emulsion. The phase separation of the
emulsion indicate the stability of the emulsion. In a theoretical way it is determine by the
HLB value of the emulsifier. HLB is stands for Hydrophilic-Lipophilic Balance.
HLB value is an empirical expression for the relationship of the hydrophilic
and lipophilic group of surfactant. By calculating the HLB value, it
enable the usage of combination surfactant to get the HLB value. The higher the
HLB value, the more water soluble the surfactant.
The
HLB value can be calculated by using this formula:
HLB
value =
|
(quantity
surfactant 1)(HLB surfactant 1) +( quantity surfactant 2)(HLB surfactant 2)
|
Quantity surfactant 1
+ quantity surfactant 2
|
The
properties and usage of HLB value is based on the purpose of the emulsion.
Table below show the HLB range and its usage :
HLB range
|
Use
|
0 – 3
|
Antifoaming agent
|
3 – 6
|
Water-in-oil
emulsifier
|
7 – 9
|
Wetting and
spreading agent
|
8 – 18
|
Oil-in-water
emulsifier
|
15 - 20
|
solubilizers
|
Therefore
in order to make the stable emulsion the first thing that we not to know is the purpose of emulsifier to give what
purpose to the emulsion. Then calculate the HLB value and start the formulation
process.
Table 1a
shows the time taken for palm oil emulsion separation to occurs until it
reaches 1cm. From the table, the interphase reach 1cm after 41 minutes 50 seconds in tube number 1. This show that
it is the most stable emulsion with the HLB value 9.67. In tube number 8, there
are no emulsifiers added, therefore the average time taken for interphase to
reach 1 cm are very fast which only takes 1 minutes 17 seconds. The palm oil
emulsion is not stable at all at this stage as it separates into distinct layer
rapidly. In conclusion, the palm oil emulsion is most stable at HLB value 9.67
provided the emulsifiers are slightly hydrophilic, hence this is an
oil-in-water emulsion.
From the table 1b, tube number 1, 2 and 3 shows
the longest time taken for arachis oil emulsion separation to occurs until it
reaches 1cm which is 95 minutes, 94 minutes and 93 minutes respectively. From
tube number 4 until 7, the emulsions are not stable because the interphase are
separated quickly. The cohesive forces are greater than adhesive forces. In
tube 8, there are no emulsifying agents added. So the emulsion is unstable and
yet the globules tend to coalescence to form big globules. In short, the
arachis oil emulsion is stable at HLB value of 9.67-11.34. Since the
emulsifiers are slightly hydrophilic, we assume this is an oil-in-water
emulsion.
From the table 1c, the olive oil emulsion at
tube 1 and 2 are stable. The interphase did not reach 1cm after 120 minutes.
After shearing, emulsifiers such as Span 20 and Tween 80 break the globules
into smaller globules to increase the surface area and hence increase surface
free energy. So the HLB values of emulsifiers are in the range of 9.67-10.37 is
the most suitable as the arachis emulsion is thermodynamically favourable at
this stage. Since the emulsifiers also slightly hydrophilic, we assume this is
an oil-in- water emulsion.
From
the table 1d, mineral oil emulsion used in tube 1 and 2 showed the same results
as the interphase did not reach 1cm after 120 minutes meaning that this
emulsion is assumed to be stable. The emulsions are thermodynamically
favourable due to the emulsifying agents form around the globules to reduce
energy of the system. From tube 3 until tube 7, the emulsions are not stable
because the interphase separated quickly and from the results taken, the
fastest is 14 minutes. This happened due to the emulsifiers failed to reduce
the interface tension and hence creaming, coalescence and breaking may occur.
Appearance, odour and colour change are the physicochemical changes in poor
emulsion. In tube number 8, there are no emulsifiers added, therefore the
average time taken for interphase to reach 1 cm are very fast which only takes
0.065minutes. The mineral oil emulsion is not stable at all at this stage as it
separates into distinct layer .Theoretically, the HLB values required for
Mineral Oil are 10 and from the results, the range of HLB value is 9.67- 10.73
and it is acceptable.
Result
( Part 2 )
Before homogenization
|
After homogenization
|
|
Picture under microscope
|
 |
 |
Texture
|
Coarse
|
Smooth
|
Consistency
|
Not homogenously dispersed
|
Homogenously dispersed
|
Degree of oily appearance
|
High
|
Low
|
Spreading of colour
|
Evenly spread
|
Evenly spread
|
Table
4
Mineral
oil 20ml
Readings
|
Viscosity (cP)
|
Average
|
|||||
1
|
2
|
3
|
4
|
5
|
6
|
||
Before
Temperature cycle
|
16.80
|
13.20
|
16.00
|
13.80
|
15.20
|
14.50
|
14.90
|
After temperature cycle
|
31.60
|
39.00
|
35.00
|
36.40
|
37.60
|
33.80
|
35.60
|
Difference (%)
|
14.90/35.60 x 100%
=41.85 %
|
||||||
Mineral
oil 25 ml
Readings
|
Viscosity (cP)
|
Average
|
|||||
1
|
2
|
3
|
4
|
5
|
6
|
||
Before
Temperature cycle
|
2.40
|
1.20
|
2.40
|
1.20
|
2.40
|
1.20
|
1.8
|
After temperature cycle
|
6.00
|
12.00
|
1.20
|
2.40
|
6.00
|
4.80
|
5.4
|
Difference (%)
|
1.8/5.4 x 100% =33.3 %
|
||||||
Mineral
oil 30ml
Readings
|
Viscosity (cP)
|
Average
|
|||||
1
|
2
|
3
|
4
|
5
|
6
|
||
Before
Temperature cycle
|
12.00
|
18.00
|
12.00
|
18.00
|
12.00
|
18.00
|
15.00
|
After temperature cycle
|
54.00
|
42.00
|
42.00
|
42.00
|
42.00
|
36.00
|
43.00
|
Difference (%)
|
15.00/43.00 x
100%=34.9 %
|
||||||
Mineral
oil 35ml
Readings
|
Viscosity (cP)
|
Average
|
|||||
1
|
2
|
3
|
4
|
5
|
6
|
||
Before
Temperature cycle
|
72.00
|
84.00
|
78.00
|
78.00
|
78.00
|
72.00
|
77.00
|
After temperature cycle
|
102.00
|
150.00
|
144.00
|
222.00
|
78.00
|
72.00
|
128.00
|
Difference (%)
|
77.00/128.00 x 100% =
66.23 %
|
||||||
Mineral Oil(ml)
|
Distance of separation
phase
|
Average
|
Ratio of
separation phase
|
||||
20
|
0.6
|
0.6
|
0.4
|
0.6
|
0.55
|
0.55/5= 0.11
|
|
25
|
1.5
|
1.2
|
1.4
|
1.3
|
1.35
|
1.35/5=0.27
|
|
30
|
3.3
|
3.3
|
3.2
|
3.2
|
3.25
|
3.25/5=0.65
|
|
35
|
2.5
|
2.5
|
2.5
|
2.5
|
2.50
|
2.5/5=0.50
|
|
Discussion
This experiment shows an obvious change of the
emulsion before and after homogenization. Before homogenization, the emulsion
is not broken down into smaller globules. Therefore, the emulsifier, acacia is
not well distributed around the globules in the emulsion. Unstable and large
globules are formed and tend to coalesce with each other. This emulsion is
unstable and tendency for destabilization process to occur is high.
Sudan solution is a
red color solution and it is used in this experiment to show the shape and
physical characteristic of the emulsion. Sudan can be used to test the presence
of lipid in the sample. Sudan solution can help to identify whether the
formulation is an oily-in-water emulsion or water-in-oil emulsion because it
can only be dissolved in the oily phase of the emulsion. This can be identified
through comparing the amount of the globules in red color and the colorless
globules. If the dispersed phase shows red color, meaning that it is an o/w
emulsion and if the continuous phase shows red color, therefore it is an w/o
emulsion.
In this experiment, there is a
significant change on emulsion before and after homogenization. Before
homogenization process occur, the size of oil globule are not consistent, there
are small and large oil globule distributed. The color of the emulsion are not
well distributed and it can be seen that some part of the emulsion appears
darker than other parts. Acacia is also not well distributed around the
globules in the emulsion. The different size globules will tends to closely
contact with each other and causes coalescence to occur, causing
destabilization of the emulsion.
After
homogenization, the oily phase will be broken down into small globules, globule
size is much smaller than before homogenization occur. The palm oil occurs have
a smoother texture and occur in a homogenous state. The oil and water phase are
dispersed evenly, and emulsifier are adsorbing on the interfacial surface of
globules, producing a stable emulsion. Therefore, we can conclude that
homogenization process helps to make the oil globules disperse evenly in the
emulsion and therefore producing a much stable emulsion when the dispersed
globules can dispersed evenly in the aqueous phase.
The function of the
ingredients used in the emulsion preparation including:
Ingredient
|
Function
|
Mineral oil
|
The oily phase in the o/w
emulsion.
|
Acacia
|
Emulsifying agent to reduce the
interfacial tension and maintain the separation of the droplets in the
dispersed phase.
|
Syrup
|
Sweetener.
|
Vanillin
|
Flavoring agent.
|
Alcohol
|
Antimicrobial agent.
|
Distilled water
|
The aqueous phase in the o/w
emulsion.
|
The amount of ingredients can influence the physical characteristics and the stability
of emulsion greatly because the amount of the palm oil used for the oily phase
and the distilled water used for the aqueous phase used is important to
determine the type of emulsion formed,, whether it is oil-in-water or
water-in-oil emulsion. Phase inversion might occur when the ratio of dispersed
phase to continuous phase is not appropriate. For example, the volume of the
dispersed phase should not more than continuous phase to avoid phase inversion
occur. The stable range for disperse phase is 30-60%. If the disperse phase
exceed 70%, the formulations will become unstable and therefore phase inversion
will occur.
Mineral
oil acts as internal phase in the oil in water emulsion. .Acacia used as an emulsifying
agent in an emulsion preparation should be used in appropriate amount according
to the HLB value. They help to stabilize emulsions preparation by
forming a hydrophilic barrier between the oil and water phases to avoid
flocculation and coalescence from occurring. If amount of acacia used is less
than required, phase separation might occur due to the large interfacial
tension formed between the dispersed phase and continuous phase.
Syrup acts as sweetener and it helps to mask the
unpleasant taste of the oil to increase patients’ compliance. However, suitable
amount of syrup must be used as non-appropriate amount of syrup will affect the
viscosity of emulsion and therefore affect the stability of the emulsion formed
Alcohol which acts
preservative to prevent the growth of microorganisms in the emulsion, however
they should not be used in excess to avoid toxicity. In the other hand,
vanillin as a flavouring agent to enhance the taste to increase the patient’s
compliance.
The physical stability
of emulsion such as creaming is the migration of the dispersed phase of an
emulsion, under the influence of buoyancy. The particles float upwards or sink,
depending on the density of dispersed phase, and also the viscosity of the
continuous phase. However as long as the particles remains separated and not
coagulating, the process is known as creaming. This process produce a product
which is not homogenous and therefore lead to poor uniform content. There is
attractive forces between the dispersed phase molecules, which attract the
droplets to come into contact with each other. When the droplets contact with
each other and forming a larger drop which decreased the droplets surface area,
coalescence occurs and this is thermodynamically unfavorable to the emulsion. The composition of palm
oil used affects the physical properties and stability of the emulsion.
According to the
theory, the separation phase ratio should be increasing with the increasing of
the mineral oil contained in the formulation. The emulsion with highest value of
separation phase ratio will produce the most unstable emulsion. Therefore, the
separation ratio should be minimize as small as possible to prepare an emulsion
with maximum stability and in homogenous condition.
The data obtained
should be increases from 20 ml oil to 35 ml oil and the separation ratio for
35ml should be greater than 30ml oil, therefore we can conclude that error has
occurred in some part of this experiment. The error occurred might be caused by
the homogenous process that was not done properly. Besides, the quality of
acacia is different for each group, so the emulsion produced might be unstable
and causes some error in the data. Furthermore, during centrifugation process,
the emulsion volume of each test tube might be not uniform and therefore
causing inaccuracy in the result.
Conclusion
The
effects of HLB surfactant on the stability of emulsion is determined.
The effects of different oil phase used in the formulation of emulsion
on the physical characteristics and stability of emulsion is determined.
