Objective:
To determine:
1.
The effects of HLB
surfactant on the stability of the emulsion.
2.
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:
Apparatus and
Material:
a. Apparatus
8 Test
tubes
1 set of 5ml pipette and bulb
A 50ml measuring
cylinder
1 50ml beaker
2 sets of pasture pipettes and
droppers A
15ml centrifugation tube
Vortex mixer Centrifugation
apparatus
Weighing boat Viscometer
1 set of mortar and
pestle Water
bath (45°C)
Light
microscope Refrigerator
(4°C)
Microscope
slides
b. Materials
Palm
oil Span
20
Arachis
oil Tween
80
Olive
oil
Sudan III solution (0.5%)
Mineral oil
Distilled water
Procedures
1.
Each test tube is
labelled and marked 1cm from the base of the test tube.
2.
4ml of oil (mineral oil)
is mixed with 4ml of distilled water into each test tube.
3. Span
20 and Tween 80 are added into the mixture of oil and water whereby the amounts
of surfactants added into each test tube are according to table 1. The test
tube is closed and the content is mixed with vortex mixer for 45 seconds. The
time needed for the interface to reach 1cm is recorded.
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
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
|
HLB value
|
9.67
|
10.73
|
11.34
|
12.44
|
13.17
|
14.09
|
15
|
0
|
Time taken for
interface to reach 1cm (mins)
|
Does not form interface after 90
minutes.
|
Does not form interface after 90
minutes.
|
Does not form interface after 90
minutes.
|
75
|
70
|
65
|
12
|
4
|
Table
2a ( mineral 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
|
HLB value
|
9.67
|
10.73
|
11.34
|
12.44
|
13.17
|
14.09
|
15
|
0
|
Time taken for
interface to reach 1cm (mins)
|
Does not form after 90 minutes
|
Does not form after 90 minutes
|
Does not form after 90 minutes
|
43
|
31
|
21
|
9
|
1
|
Table
2b ( Arachis 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
|
HLB value
|
9.67
|
10.73
|
11.34
|
12.44
|
13.17
|
14.09
|
15
|
0
|
Time taken for
interface to reach 1cm (mins)
|
Does not form after 90 minutes
|
Does not form after 90 minutes
|
58
|
12
|
32
|
14
|
38
|
0.25
|
Table
2c ( 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
|
HLB value
|
9.67
|
10.73
|
11.34
|
12.44
|
13.17
|
14.09
|
15
|
0
|
Time taken for
interface to reach 1cm (mins)
|
Does not form after 90 minutes
|
Does not form after 90 minutes
|
86
|
60
|
80
|
113
|
85
|
15
|
Table
2d ( Palm Oil)
4. The HLB value for each
sample is calculated.
Tube
no.
|
Span
20 (drops)
|
Tween
80 (drops)
|
Calculations (HLB):
|
HLB
value
|
1
|
15
|
3
|
 |
9.67
|
2
|
12
|
6
|
 |
10.73
|
3
|
12
|
9
|
 |
11.34
|
4
|
6
|
9
|
 |
12.44
|
5
|
6
|
15
|
 |
13.17
|
6
|
3
|
18
|
 |
14.09
|
7
|
0
|
15
|
 |
15
|
8
|
0
|
0
|
 |
Table 3
5.
A few drops of Sudan III
solution are added to (1g) emulsion formed in a weighing boat and are mixed
homogenously. The spread of the colour in the sample are compared and recorded.
Samples are taken and spread on a microscope slides and observed under the
light microscope.
Tube no. |
Images
|
HLB value
|
Colour
|
Appearance
|
1
|
 |
9.67
|
Sudan III colour dispersed in the emulsion. The colour of the
stained in the emulsion is light orange in colour.
|
The water droplets are dispersed in the oil. Therefore it is
water in oil emulsion(w/o),. However, it does not dispersed well.
|
2
|
 |
10.73
|
Sudan III colour dispersed in the emulsion. The colour of the
stained in the emulsion is light orange in colour
|
Water droplets dispersed better in oil. This is a water in oil
emulsion but the HLB value in this test tube is not in the optimum range.
|
3
|
 |
11.34
|
Sudan III colour dispersed in the emulsion. The colour of the
stained in the emulsion is light orange in colour
|
The water droplets dispersed the best in oil. Therefore, it is a
water in oil emulsion.
|
4
|
 |
12.44
|
Sudan III colour dispersed in the emulsion. The colour of the
stained in the emulsion is light orange in colour
|
|
5
|
 |
13.17
|
Sudan III colour dispersed in the emulsion. The colour of the
stained in the emulsion is light orange in colour
|
Water droplets does not dispersed well in oil. The HLB value of
the emulsion in the test tube is not in the optimum range too.
|
6
|
 |
14.09
|
Water droplets are not dispersed properly in oil. The HLB value
of the emulsion in this test tube is not in the optimum range.
|
|
7
|
 |
15
|
Sudan III colour dispersed in the emulsion. The colour of the stained in the emulsion is light orange in colour |
Water droplets does not dispersed properly in the oil. Irregular
sizes og globules can be seen. The HLB value of the emulsion is not in the
optimum range too.
|
8
|
 |
0
|
Sudan III does not disperse in the emulsion whereby the globules of the Sudan red forms on the surface. |
No emulsion is formed because there is no surfactant present.
Distinct phase can be seen and phase separation occur very fast.
|
Table 4
6.
Mineral Oil Emulsion
(50g) is prepared from the formulation below by using wet gum method according
to Table 5a & 5b.
Mineral Oil
|
(refer
Table 3b)
|
Acacia
|
6.25 g
|
Syrup
|
5 ml
|
Vanillin
|
2 g
|
Alcohol
|
3 ml
|
Distilled water qs |
50 ml
|
Table
5a
Emulsion
|
Group |
Mineral Oil (ml)
|
I
|
1,5
|
20
|
II
|
2,6
|
25
|
III
|
3,7
|
30
|
IV
|
4,8
|
35
|
Table 5b
7.
40g of the emulsion is placed into a
50ml beaker and homogenized for 2 minutes using a vortex mixer.
8. 2g of the emulsion is taken (before and after homogenization) 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 under the light microscope is stated and compared.
9.
The viscosity of the emulsion formed after
homogenization is determined (15g in 50ml beaker) 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. Step 9 is
repeated again and an average value is obtained.
Result:
I.
Comparison
of mineral oil emulsion before and after homogenization
Mineral
Oil Emusion 20ml
Before
homogenization
|
After
homogenization
|
|
Texture
|
Coarse
|
Smooth
|
Consistency
|
Less stable
|
Stable
|
Degree
of oily appearance
|
More greasy, more globules with
irregular size
|
Less greasy, less globules with
uniform size
|
Spreading
of colour
|
Spread unevenly
|
Spread evenly
|
Mineral
Oil Emulsion 25ml
Before homogenization
|
After homogenization
|
|
Texture
|
Coarse
|
Smooth
|
Consistency
|
Less
stable
|
Stable
|
Degree of oily appearance
|
More
greasy, spherical globule
|
Less
greasy and spherical globule
|
Spreading of colour
|
Spread
evenly
|
Spread
evenly
|
Mineral
Oil Emulsion 30ml
Before homogenization
|
After homogenization
|
|
Texture
|
Coarse
and not homogenous
|
Smooth
and homogenous
|
Consistency
|
Less
stable
|
Stable
|
Degree of oily appearance
|
More
greasy, spherical globule
|
Less
greasy and spherical globule
|
Spreading of colour
|
Spread
evenly
|
Spread
evenly
|
Mineral
Oil Emulsion 35ml
Before homogenization
|
After homogenization
|
|
Texture
|
Smooth
and homogenous
|
Smooth
and homogenous
|
Consistency
|
Less
stable
|
Stable
|
Degree of oily appearance
|
More
greasy
|
Less
greasy
|
Spreading of colour
|
Spread
evenly and widely
|
Closely
spread
|
II.
Viscosity
of Mineral Oil Emulsion
Mineral
Oil Emulsion 20ml
Readings
|
Viscosity(cP)
|
Average
|
|||||
1
|
2
|
3
|
4
|
5
|
6
|
||
Before temperature cycle
|
42
|
42
|
36
|
24
|
30
|
24
|
33
|
After temperature cycle
|
48
|
45
|
40
|
30
|
38
|
36
|
39.5
|
Difference (%)
|
39.5
– 33 / 33 x 100% = 19.70%
|
||||||
Mineral
Oil Emulsion 25ml
Readings
|
Viscosity(cP)
|
Average
|
|||||
1
|
2
|
3
|
4
|
5
|
6
|
||
Before temperature cycle
|
72
|
84
|
78
|
78
|
78
|
72
|
77
|
After temperature cycle
|
102
|
150
|
144
|
222
|
78
|
72
|
128
|
Difference (%)
|
128
77 / 77 x 100% = 66.23%
|
||||||
Mineral
Oil Emulsion 30ml
Readings
|
Viscosity(cP)
|
Average
|
|||||
1
|
2
|
3
|
4
|
5
|
6
|
||
Before temperature cycle
|
273
|
450
|
420
|
418
|
416
|
422
|
400
|
After temperature cycle
|
228
|
216
|
222
|
218
|
220
|
222
|
221
|
Difference (%)
|
221
– 400 / 400 x 100% = -44.75%
|
||||||
Mineral
Oil Emulsion 35ml
Readings
|
Viscosity(cP)
|
Average
|
|||||
1
|
2
|
3
|
4
|
5
|
6
|
||
Before temperature cycle
|
360
|
394
|
398
|
425
|
394
|
452
|
404
|
After temperature cycle
|
1080
|
1125
|
1132
|
1160
|
1002
|
1055
|
1092
|
Difference (%)
|
1092
– 404 / 404 x 100% = 170.30%
|
||||||
III. Ratio
of Height Separation
Mineral oil
(ml)
|
Ratio of
separation phase (x/y)
|
Average
|
|||
20
|
0.6
|
0.6
|
0.4
|
0.6
|
0.55
|
25
|
0.3
|
0.24
|
0.28
|
0.26
|
0.27
|
30
|
0.58
|
0.6
|
0.56
|
0.58
|
0.58
|
35
|
0.5
|
0.5
|
0.5
|
0.5
|
0.50
|
(35ml-Before homogenization) (35ml- After homogenization)
Discussion:
Through
this experiment, we are required to determine the effects of HLB surfactant on
the stability of the emulsion. The optimum stability of O/W emulsions are
stabilized by 1:1 molar ratios of Spans and Tweens is due to association
between the emulsifier molucules adsorbed at the oil-water interface. According
to the results, mineral oil emulsion 25ml and 30ml are more stable than mineral
oil emulsion 20ml and 35ml.
In
this experiment, Sudan III solution is a dye that can stain the oil phase.
Sudan III solution is usually used to determine the type of emulsion, whether
is an O/W emulsion or W/O emulsion. The emulsion produced in this experiment is
an O/W emulsion; this is because the globules observed under the microscope are
stained with Sudan III solution. Hence, we can conclude that the mineral oil
phase is dispersed phase while water is the continuous phase.
According
to the results, the size of the globule increase as the mineral oil to water
ratio increase. This is because the volume of mineral oil per globule will
increase and causes the size of the globule to increase. After homogenization,
all unstable emulsion becomes stabilized. This is due to homogenization can
make the globule smaller as the vibration force can break the big globule into
smaller globules.
Before
homogenization, all of the emulsions are greasy because the oil phase and water
phase are not well mixed yet. Thus, it will look and feel greasy. But after
homogenization, the water and oil phase are mixed in a well manner and causes the
oil globules are completely surrounded by water. Hence, the emulsions become
less greasy.
Phase volume ratio is
the ratio of dispersed phase to that of continuous phase which is used widely
to determine the stability of an emulsion. The choice of the phase volume ratio
of an emulsion is depends on a number of factors, including the required
consistency. It is inadvisable to formulate emulsions containing < 25% of
disperse phase as the product will be very susceptible to severe creaming or
sedimentation problems. On the other hand, if an emulsion containing too high
proportion of dispersed phase, phase inversion may likely to occur. Hence an
emulsion with phase volume ratio of 50:50 is usually stable. As we can see
based on the results, emulsions with mineral oil 25ml and 30ml are more stable
than the other two. The dispersed phase of both the emulsions is evenly spread.
The purpose of having the temperature cycle on the emulsions
is to test the stability of the emulsions in long term storage, shelf life of
the emulsions. Viscosity of the emulsions is measured before and after the
temperature cycle in order to calculate the different between the two values. A
smaller difference in the viscosity before and after the test shows the
emulsion has a higher stability as it means less changes are happened in term
of chemical as well as physical properties of the emulsion. According to the
results, emulsion with 20ml of mineral oil has the smallest difference in
viscosity. However, the most stable emulsion should be emulsion with 25ml of
mineral oil, this maybe due to the errors conducted throughout the experiment
like insensitivity of the viscometer.
The sample of emulsions
are also subjected to centrifugation in order to test the rate of sedimentation
which will directly influence the stability of the emulsions. The higher the
ratio of separation phase, the lower the stability of the emulsions as more
proportion of the two phases are separated. In the results, the emulsion with
25ml of mineral oil shows the least ratio of separation, hence it has the
greatest stability among the other emulsions. However, this may not be accurate
as the evaluation process itself may damage the emulsion structure.
Conclusion:
Combination of appropriate amount of surfactants will give an accurate and effective HLB value which will form a stable emulsion. Higher amount of oil will contribute to a higher viscosity of the emulsion. Lastly, 25ml of mineral oil shows the least ratio of separation which means it is most stable, hence, an emulsion with phase volume ratio of 50:50 is usually more stable.
Reference:
1. Florence, A.T. & Atwood, D. 2011. Physicochemical Principles of Pharmacy. 4thedition. London: Pharmaceutical Press
2. Rosen MJ and Kunjappu JT (2012). Surfactants and Interfacial Phenomena (4th ed.). Hoboken, New Jersey: John Wiley & Sons.
3. https://books.google.com.my/books?id=93GWi1OvfRMC&pg=PA80&lpg=PA80&dq=emulsion+hlb+different+oil&source=bl&ots=0wJNOP9xMV&sig=iLyyIU3smDChd4yXGlF31uNK4-A&hl=en&sa=X&redir_esc=y#v=onepage&q=emulsion%20hlb%20different%20oil&f=false
Conclusion:
Combination of appropriate amount of surfactants will give an accurate and effective HLB value which will form a stable emulsion. Higher amount of oil will contribute to a higher viscosity of the emulsion. Lastly, 25ml of mineral oil shows the least ratio of separation which means it is most stable, hence, an emulsion with phase volume ratio of 50:50 is usually more stable.
Reference:
1. Florence, A.T. & Atwood, D. 2011. Physicochemical Principles of Pharmacy. 4thedition. London: Pharmaceutical Press
2. Rosen MJ and Kunjappu JT (2012). Surfactants and Interfacial Phenomena (4th ed.). Hoboken, New Jersey: John Wiley & Sons.
3. https://books.google.com.my/books?id=93GWi1OvfRMC&pg=PA80&lpg=PA80&dq=emulsion+hlb+different+oil&source=bl&ots=0wJNOP9xMV&sig=iLyyIU3smDChd4yXGlF31uNK4-A&hl=en&sa=X&redir_esc=y#v=onepage&q=emulsion%20hlb%20different%20oil&f=false
Photos taken:
Extra Information:
No comments:
Post a Comment