Date of Experiment : 6th October 2015
Apparatus
Result Activity 1
Objective
To
study the effects of HLB surfactant on the stability of the
emulsion and the effects
of different oil phases used in the formulation on the physical characteristics
and stability of the emulsion.
Introduction
Emulsion is a two-phase system that is not stable
thermodynamically. It contains at least two immiscible liquids where one of
them (internal/dispersed phase) is dispersed homogenously in another liquid
(external/continuous phase). In general, emulsion can be categorised into 2
types, oil-in-water emulsion (o/w) and water-in-oil emulsion (w/o). Emulsion is
stabilised 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
Apparatus
8 Test tubes
1 set of 5ml pipette and bulb
1 set of 5ml pipette and bulb
A 50ml measuring cylinder
1 50ml beaker
1 50ml beaker
2 sets of pasture pipettes and droppers
A 15ml centrifugation tube
A 15ml centrifugation tube
Vortex mixer
Centrifugation apparatus
Centrifugation apparatus
Weighing boat
Viscometer
Viscometer
1 set of mortar and pestle
Water bath (45°C)
Water bath (45°C)
Light microscope
Refrigerator (4°C)
Refrigerator (4°C)
Microscope
slides
Materials
Palm oil
Span 20
Span 20
Arachis oil
Tween 80
Tween 80
Olive oil
Sudan III solution (0.5%)
Sudan III solution (0.5%)
Mineral oil
Distilled water
Distilled water
Procedure
1.
Each test tube is labelled and 1cm from
the base of test tube is marked.
2.
4mL of Arachis oil and 4mL of distilled
water are mixed into the test tube.
Activity
1
1. Span
20 and Tween 80 are added into the
mixture of oil and water according to table 1. 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 is repeated in order to obtain an average HLB value of
a duplicate.
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
|
Table 1
2. A
few drops of Sudan III solution is added to (1g) emulsion formed in a weighing
boat and mixed homogenously. The spread of the colour in the sample is
compared. Some of the sample is spread on a microscope slide and observed under
light microscope. The appearance and globule size formed is drawn and described.
Activity 2
1.
A Mineral
Oil Emulsion (50g) is prepared from the formulation below by using wet gum method.
Mineral Oil
|
25 mL
|
Acacia
|
6.25 g
|
Syrup
|
5 mL
|
Vanillin
|
2 g
|
Alcohol
|
3 mL
|
Distilled water qs
|
50 mL
|
2.
40g
of emulsion placed into a 50ml beaker and homogenized for 2 minutes using a
vortex mixer.
3.
2g of emulsion
(before and after homogenization) are taken and placed into a weighing boat and
labeled. A few drops of Sudan III solution are added and mixed. The texture,
consistency, degree of oily appearance and the spreading of colour in the
sample is stated and compared under the light microscope.
4.
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°C (water bath) for 15 minutes and then to 4°C (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. Same step is repeated again and an average value is
obtained.
5.
5g of homogenised emulsion is placed into a centrifugation tube and
centrifuged (4500 rpm, 10 minutes, 25°C). The height of the separation formed
is measured and the ratio of the height separation is determined.
ARACHIS
OIL
A)
The Time Taken for Arachis Oil Emulsion Interface to reaches 1cm
Tube
no.
|
1
|
2
|
3
|
4
|
5
|
6
|
7
|
8
|
Phase
separation time(min)
|
Interface
do not reach 1 cm even after 125 minutes
|
98
|
83
|
66.20
|
51.45
|
44.31
|
33.48
|
27.54
|
PALM OIL:
The Time Taken for Palm Oil Emulsion Interface
to reaches 1cm
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)
|
2:36:58
|
2:13:00
|
1:26:00
|
1:00:00
|
1:20:00
|
1:53:00
|
1:25:00
|
0:15:00
|
OLIVE OIL
The Time Taken for Olive Oil Emulsion Interface to reaches 1cm
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
|
MINERAL
OIL
The Time Taken for Mineral Oil Emulsion Interface to reaches 1cm
Tube no.
|
Span 20 (drops)
|
Tween 80 (drops)
|
Time for phase separation
(min)
|
Stability
|
||
T1
|
T2
|
Average
|
||||
1
|
15
|
3
|
Interphase did not reach 1cm after 120 minutes
|
Interphase did not reach 1cm after 120 minutes
|
-
|
Most stable
|
2
|
12
|
6
|
Interphase did not reach 1cm after 120 minutes
|
Interphase did not reach 1cm after 120 minutes
|
-
|
Most stable
|
3
|
12
|
9
|
70
|
69
|
69.5
|
Moderate
|
4
|
6
|
9
|
63
|
60
|
61.5
|
Moderate
|
5
|
6
|
15
|
55
|
57
|
56
|
Moderate
|
6
|
3
|
18
|
45
|
47
|
46
|
Moderate
|
7
|
0
|
15
|
12
|
16
|
14
|
Least stable
|
8
|
0
|
0
|
0.08
|
0.05
|
0.065
|
Least stable
|
B)
HLB value of each tube
HLB
of Span 20= 8.6
HLB
of Tween 80= 15
HLB
value = (quantity surfactant 1) (HLB surfactant 1) + (quantity surfactant
2) (HLB
surfactant 2)
_______________________________________________________________
quantity surfactant 1 + quantity surfactant 2
Test
tube 1 = 15(8.6) + 3 (15)
/ (15+3)
= 9.67
Test
tube 2 = 12(8.6) + 6( 15)
/ (15+3)
= 10.73
Test
tube 3 = 12(8.6) + 9(15) /
(15+3)
= 11.34
Test tube 4 = 6( 8.6) + 9(15) / (15+3)
= 12.44
Test tube 5 = 6( 8.6) + 15(15) / (15+3)
= 13.17
Test tube 6 = 3( 8.6) + 18(15) / (15+3)
= 14.09
Test tube 7 = 0( 8.6) + 15(15) / (15+3)
= 15.00
Tube No.
|
1
|
2
|
3
|
4
|
5
|
6
|
7
|
8
|
HLB value
|
9.67
|
10.73
|
11.34
|
12.44
|
13.17
|
14.09
|
15.00
|
-
|
C) Spreading of
the colour in the sample
In this experiment, a few drops of Sudan
III solution is added to (1g) emulsion in a weighing boat and mix
homogenously.After mixing, the orange-red colour of Sudan III spreading less
evenly from weighing boat sample 1 to weighing boat sample 8. At weighing boat sample
1, Sudan III seem to be mixed
homogenously with the emulsion and the colour appeared to be even. But at
weighing boat 8, Sudan III did not mixed very well with the emulsion and looked a little bit brownish.
D)
The globule appearance
Under microscope examination, the globules
are small sphere but the size of globules are varies from sample of test tube 1
to sample test tube 8. This is due to the amount or quantity of surfactant
(Span 20, Tween 80) that has been added to the emulsion. HLB value of emulsion
in test tube 8 is 0, since there is no surfactant used thus the shape globule
of emulsion in tube 8 in appeared to be irregular shape and largest in size.
Meanwhile the smallest size with spherical shape of globule can be seen in test
tube 1. In conclusion, the higher the value of HLB and less presence of
surfactant, the larger the size of globules formed.
Result
For Activity 2 (Mineral Oil Emulsion)
I)
Sample
Under Microscope
 |
| Before Homogenization |
 |
| After Homogenization |
I)
COMPARISON
BEFORE
HOMOGENIZATION
|
AFTER
HOMOGENIZATION
|
|
TEXTURE
|
Coarse
|
Smooth
|
CONSISTENCY
|
Not homogenously dispersed
|
Homogenously dispersed
|
DEGREE
OF OILY APPEARANCE
|
High degree of oil
|
Low degree of oil
|
SPREADING
OF COLOUR
|
Colour spread evenly
|
Colour spread evenly
|
II)
VISCOSITY
OF EMULSION
A)
MINERAL
OIL (20 ML)
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
|
DIFFERENCES(%)
|
14.90
/ 35.60 X 100 = 41.85 %
|
||||||
B)
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
|
DIFFERENCES(%)
|
1.8
/ 5.4 X 100 = 33.3%
|
||||||
C)
MINERAL
OIL (30 ML)
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
|
DIFFERENCES(%)
|
15.00
/ 43.00 X 100 = 34.9%
|
||||||
D)
MINERAL
OIL (35 ML)
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
|
150
|
144
|
222
|
78
|
72
|
128.00
|
DIFFERENCE
(%)
|
77.00
/ 128.00 X 100 = 66.23 %
|
||||||
I)
RATIO
OF THE HEIGHT SEPARATION
MINERAL
OIL
(mL)
|
RATIO
OF SEPARATION PHASE
|
AVERAGE
(x)
|
RATIO
OF SEPARATION PHASE (x/y)
|
||||||||
I
|
II
|
III
|
IV
|
||||||||
25
|
1.5
|
1.2
|
1.4
|
1.3
|
1.35
|
1.35
/ 5 = 0.27
|
|||||
20
|
0.6
|
0.6
|
0.4
|
0.6
|
0.55
|
0.55 / 5 =
0.11
|
|||||
30
|
0.7
|
0.7
|
0.6
|
0.6
|
0.65
|
0.65 / 5 = 0.13
|
|||||
35
|
2.5
|
2.5
|
2.5
|
2.5
|
2.5
|
2.5 / 5 = 0.50
|
|||||
x: height of the oil in the centrifuge tube
y: height of the total emulsion in the
centrifuge tube
Discussion
Activity 1
Activity 1
The
stability of emulsion in the presence of surfactant has been studied and
compared. Two types of surfactants were selected which are Span 20 and Tween
80. In this experiment, HLB (Hydrophile-Lipophile Balance) method is used to
determine the ratio of hydrophobic to the lipophilic portion of a
molecule. Since emulsion is a mixture of
water and oil and it is thermodynamically unstable, changes of emulsion
properties will occur, the more slowly the properties change, the more stable
the emulsion is. It need an emulsifying agent for the emulsion to stay in one
phase and not separated over a certain period of time. Type of oil also may
play an important role in determining the stability of the emulsion. In this
experiment, our group used Arachis oil. Theoretically, the time taken for the
emulsion to separate into two phases and for the interface to reach 1 cm is
longer when the HLB value is at the lowest compared to the higher HLB values. This
is because, surfactants with high HLB values will be more water soluble and
those with low HLB values are more oil soluble.
Based
on the result from our group, test tube 1 with the HLB values to form stable
emulsion containing arachis oil are 10.73. They did not form a separate phase
of 1 cm after 120 minutes which means they required longer time for phase to
separate. This means that the stable emulsion of arachis oil can be prepared by
adding 12 drops of Span 20 and 6 drops of Tween 80. Meanwhile, the results from
group 6 shows no emulsion which their time for phase separation is more than
120 minutes. The inconsistency of results may be caused by error in handling
and mixing of the substances used in the experiment by the person in charge. For
both group, the emulsion in test tube 8 is the least stable emulsion since
there is no emulsifier added into emulsion to stabilize it.
For
palm oil emulsion, the result from other group shows that 10.73 and 9.67 from test tube 1 and 2 are the HLB
values that needed to form stable emulsion. They did not form a separate phase
of 1 cm after 120 minutes. On the other hand, emulsion from test tube 8 give
the lowest stability where the phase separation time is the shortest since
there is no emulsifier added into emulsion to stabilize it. Thus, the emulsion
just separated into 2 phase within 15 seconds.
For
olive oil emulsion, the result from other group shows that 10.73 and 9.67 from
test tube 1 and 2 are the HLB values that needed to form stable emulsion. They
did not form a separate phase of 1 cm after 120 minutes. Meanwhile, emulsion
from test tube 8 give the lowest stability where the phase separation time is
the shortest since there is no emulsifier added into emulsion to stabilize it.
Thus, the emulsion just separated into 2 phase within 16.5 seconds.
For
mineral oil emulsion, the result from other group also shows that 10.73 and
9.67 from test tube 1 and 2 are the HLB values that needed to form stable
emulsion. They did not form a separate
phase of 1 cm after 120 minutes. On the other hand, emulsion from test tube 8
give the lowest stability where the phase separation time is the shortest since
there is no emulsifier added into emulsion to stabilize it. Thus, the emulsion
just separated into 2 phase within average 0.65 second.
In
short, the HLB value that range from 9-11 are the most stable emulsion. Thus,
the emulsions formed containing 4 types of oils respectively are water in oil
emulsion. Obviously, the results obtained is quite different regarding the
theory. This may be due to error while handling the experiment or mixing the
incorrect amount of surfactants into the emulsion.
Sudan ΙΙΙ solution is used in this experiment to indicate the position of oily
globules in the emulsion and also the type of emulsion either oil in water
(o/w) emulsion or water in oil (w/o) emulsion. Sudan ΙΙΙ solution has a red
colour and it will dissolve in the oil phase to give a red colour to the oily
globules. The aqueous globules will not be stained red and appear as colourless
globules. Based on our results, at weighing boat sample
1, Sudan III seem to be mixed
homogenously with the emulsion and the colour appeared to be even. But at
weighing boat 8, Sudan III did not mixed very well with the emulsion and looked a little bit brownish. Furthermore,
most of the emulsion from different type of oil used also shows the same
results. So it can be concluded that the emulsion with 15 drops of Span 20 and
3 drops of Tween 80 is a water in oil emulsion and has uniform dispersion on a colourless background due to the present of
emulsifier.
Activity 2
In this experiment, the
emulsion produced using wet gum method is oil in water emulsion In producing
this emulsion, several excipients are needed to ensure that the emulsion
produced is stable. Acacia acts as a surfactant to ensure the dispersed phase
can be dispersed and incorporate evenly in the continuous phase. Acacia also
lower the possibilities of emulsion to undergo creaming or breaking process.
Syrup is used to provide viscosity for the emulsion to prevent the droplets in
the emulsion to merge together. Lastly, alcohol is used as an antimicrobial
agent to prolong the storage time of the emulsion by preventing the growth of
microorganism.
The first experiment is
to observe the size, the texture, consistency, degree of oily appearance and
spreading of colour in the emulsion. The purpose of homogenization is to homogenize
the two immisible liquid into a smooth emulsion by making the droplets into
extremely small particles dispersed evenly in the continuous phase. In this
experiment, homogenization plays it role by further breaking the droplets into
extremely small droplets. Sudan III is used as a dye to provide a better view
of the droplets of the emulsion under the microscope. From the result obtained,
the size of droplets after homogenization is obviously smaller than the
droplets of emulsion before homogenization. Besides, after the homogenization,
the emulsion become less viscous and has more watery appearance compare to the
emulsion before homogenization.
The temperature cycle
is used to test the physical stability of the emulsion by passing through the
emulsion to water bath of 45 degree Celsius for 30 minutes and then keep it in
the freezer for the next 30 minutes. When the emulsion is in the water bath,
increase in temperature will lead in increasing in the kinetic energy of the
particles inside the emulsion, the particles will more likely to collide with
each other and hence the emulsion will undergo phase separation and coalescence
easily. This will reduce the viscosity of the emulsion. Then, when they are
passing through the cold temperature, the iced crystal will form around the
droplets. This will increase the viscosity of the emulsion. This is based on
the theory that a fluid's viscosity strongly depends on its temperature. Along
with the shear rate, temperature really is the dominating influence. The higher
the temperature is, the lower a substance's viscosity is. Consequently,
decreasing temperature causes an increase in viscosity. The relationship
between temperature and viscosity is inversely proportional for all substances.
A change in temperature always affects the viscosity and it depends on the substance just how much
it is influenced by a temperature change. For some fluids a decrease of 1°C
already causes a 10 % increase in viscosity. In this experiment , all groups
with different volume of mineral oil used shows that the emulsion that
undergoes temperature cycle has much more higher viscosity than before the
temperature cycle . Volume of mineral oil used is actually will affect the
reading of viscosity too . The higher the volume of oil used , the higher the viscosity will be as the oil droplets will
thicken more with the water droplets. However , we couldn’t conclude the effect
of volume of mineral used among the different groups against viscosity due to different
used of spindle size if the viscosity
meter . Therefore the constant reading based on the spindle size is not achieved
. However ,from using 20 ml and 35 ml of mineral oil that used same size of spindle
, it can be proved the 35 ml of mineral oil show higher viscosity which is
128(after temperature cycle) while 20 ml got much more lower viscosity which is
36.50 . So , it can beconcluded that the higher the volume , the higher the
viscosity.
Lastly, in this
experiment, the ratio of separation phase also being conducted to test the
stability of the emulsion. High ratio of separation phase indicates the
emulsion is unstable because the continuous phase and the dispersed phase can
be separated easily.Theoritically ,the higher the volume of mineral oil used ,
the higher the chance for the phase separation of the oil and water .
Above is the graph of
volume of mineral oil agains ratio of phase separation . However , the rise in
the ration of separation phase is not constant where we can see that there is increase
with 25 ml and then sudden decrease with 30 ml of oil . This result is may due
to some error occur during the experiment.For example, 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.
Conclusion
The HLB value that range from 9-11 are the most stable emulsion and emulsions formed containing 4 types of oils respectively are water in oil emulsion.
The size of droplets after homogenization is smaller than the droplets of emulsion before homogenization due to reduction process during the homogenization process.The higher the volume of oil phase , the higher the ratio of separation phase shows that the emulsion is unstable because the continuous phase and the dispersed phase can be separated easily .
References
