The objective of this experiment is to study and evaluate the effects of different content materials on the physical characteristics of the formed suspension.
Introduction:
Emulsion is a 2 phase system
that is thermodynamically not stable. It contains at least 2 immiscible liquids
in which one of the phase (internal / dispersed phase) is distributed
homogenously in the other liquid phase (external / continuous phase). Emulsion
can be classified into 2 types that are oil in water emulsion (o/w) and water
in oil emulsion (w/o). Emulsion is stabilized using the emulsifying agents. The
emulsifying agent can be classified into 4 types, which are hydrophilic
colloid, fine solid particles, surface active agent and surfactant.
| The HLB (hydrophilic-lipophilic balance) method has been used to determine the quantity and the type of surfactant needed to be used to prepare a stable emulsion. Every surfactant is given a number in the HLB scale which is ranged from 1 (lipophilic) until 20 (hydrophilic). Normally, the usage of 2 emulsifying agents will form a very stable emulsion preparation. The HLB value can be determine using the equation below: |
 |
Apparatus
150 ml measuring cylinder 1 50 ml beaker
2 Sets of Pasture pipette and droppers 1 15 ml Homogenizer tube
Vortex mixer Homogenizer
Weighing boat Viscometer
1 set of mortar & pestle Water bath (45 oC)
1 set of mortar & pestle Water bath (45 oC)
Light microscope Refrigerator
4 oC
Microscopic slide
Reagents
Turpentine oil Tween
80
Arachis oil Sudan
III solution (0.5%)
Olive oil
Distilled water
Procedures:
1. Each test tube is labeled and 1cm from the bottom is
marked on the test tubes.
2. 4 ml of oil (referred to table) and 4 ml of distilled
water are mixed in the test tube.
Group
|
Type of
oil
|
1,5
|
Palm oil
|
2,6
|
Arachis oil
|
3,7
|
Olive oil
|
4,8
|
Mineral oil
|
3.
Span 20 and
Tween 80 are dropped into the mixture of oil and water, according to the amount
given in the table below. The test tube is closed and the mixture is mixed
using the Vortex mixer for about 45 seconds. The time taken for separation
phase to occur until the 1 cm mark is reached, is recorded. The HLB value for
each sample is determined.
Table II
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.
Few drops of the
Sudan III solution are dropped into 1 g of each of the emulsion produced, in
the weighing boats. The color dispersion in the sample is described and
compared with the other emulsion formulations. Some of the emulsion is put on
the microscopic slide and observed under the light microscope. The appearance
and globule size formed are determined and drawn.
5. The Turpentine Oil Emulsion (50g) is prepared using
the formulation below, by using the wet gum method:
6.
40 g of the
emulsion produced is placed in a 50 ml beaker and homogenization is done for 2
minutes using a homogenizer.
BEFORE AND AFTER HOMOGENIZATION PROCESS
7. 2 g of the sample formed before and after being homogenized is taken out and placed in the weighing boats. Few drops of Sudan III solutions are dropped into the emulsion and stirred. The texture, consistency, greasiness appearance and color dispersion are determined and compared by observing under the light microscope.
8.
15g of the
emulsion after homogenization is taken out and the viscosity is determined
using the viscometer that has been calibrated using the “Spindle” LV-4 type.
The sample is exposed to temperature 45 oC for about 30 minutes and
then to 4 oC (refrigerator) for 30 minutes. The viscosity of the
emulsion after the temperature cycle is determined after it achieves room
temperature (10-15 minutes).
9.
5g of the
homogenized emulsion is put into a homogenizer tube and is centrifuged in
4500rpm, for 30 minutes at 25 oC. The separation height
produced is measured and the separation height ratio is determined.
Results:
1.
The time
required to get a separated phase of 1 cm.
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
|
HLB value
|
9.67
|
10.73
|
11.34
|
12.44
|
13.17
|
14.09
|
15.00
|
0.00
|
Phase separation time (min)
|
-
|
-
|
-
|
37.00
|
45.50
|
42.00
|
20.50
|
3.75
|
Stability
|
Yes
|
Yes
|
Yes
|
No
|
No
|
No
|
No
|
No
|
For
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
|
15.00
|
0.00
|
Phase separation time (min)
|
-
|
-
|
-
|
32.50
|
44.50
|
58.00
|
19.00
|
17.00
|
Stability
|
Yes
|
Yes
|
Yes
|
No
|
No
|
No
|
No
|
No
|
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
|
HLB value
|
9.67
|
10.73
|
11.34
|
12.44
|
13.17
|
14.09
|
15.00
|
0.00
|
Phase separation time (min)
|
-
|
-
|
8.19
|
14.48
|
75.18
|
58.35
|
32.25
|
1.40
|
Stability
|
Yes
|
Yes
|
No
|
No
|
No
|
No
|
No
|
No
|
For
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
|
15.00
|
0.00
|
Phase separation time (min)
|
-
|
50.00
|
24.00
|
61.00
|
54.50
|
24.05
|
13.00
|
0.50
|
Stability
|
Yes
|
No
|
No
|
No
|
No
|
No
|
No
|
No
|
2.
Size and
physical appearance of the globule formed in each emulsions containing
different oils and surfactant of different HLB values.
For the
test tube 4, the globule size is considered small and closely packed together. The
bigger globules are surrounded by many small globules. While for test tube 5
and 6, the globules are slightly larger than test tube 4, and also surrounded
by small globules but not as much as test tube 4.The bigger globule of test
tube 6 is bigger than test tube 5.And for the test tube 7, the globules formed
are much larger and dispersed quite far away from each other. For the last test
tube, the globules formed are the biggest among all the test tubes and the
globules are far away from each other.
 |
| picture from test tubes 4,5,6,7 |
 |
3. Viscosity of
emulsion:
I.
Emulsion
1: 20 ml palm oil
Reading
|
Viscosity (cP)
|
Mean ± SD
|
|||||
1
|
2
|
3
|
4
|
5
|
6
|
||
Before temperature cycle
|
80
|
90
|
100
|
100
|
110
|
120
|
100.00±14.14
|
After temperature cycle
|
90
|
100
|
100
|
130
|
140
|
140
|
116.67±22.51
|
Difference (%)
|
16.67%
|
||||||
II.
Emulsion
II : 25ml arachis oil
Reading
|
Viscosity (cP)
|
Mean ± SD
|
|||||
1
|
2
|
3
|
4
|
5
|
6
|
||
After temperature cycle
|
779.8
|
779.8
|
659.9
|
857.9
|
842.9
|
731.9
|
775.37±72.98
|
Difference (%)
|
89.16%
|
||||||
III.
Emulsion
III (30ml olive oil)
Reading
|
Viscosity (cP)
|
Mean ± SD
|
|||||
1
|
2
|
3
|
4
|
5
|
6
|
||
Before temperature cycle
|
239.9
|
210
|
210
|
50
|
60
|
50
|
136.65±92.00
|
After temperature cycle
|
539.9
|
449.9
|
389.9
|
50
|
50
|
50
|
254.95±229.53
|
Difference (%)
|
86.57%
|
||||||
IV.
Emulsion
IV (35ml mineral oil)
Reading
|
Viscosity (cP)
|
Mean ± SD
|
|||||
1
|
2
|
3
|
4
|
5
|
6
|
||
Before temperature cycle
|
650
|
650
|
600
|
740
|
820
|
920
|
730±121.66
|
After temperature cycle
|
300
|
300
|
300
|
900
|
920
|
960
|
613.33±343.78
|
Difference (%)
|
-15.98%
|
||||||
4. Separation Height
Mineral
Oil(ml)
|
Ratio of separation
phase
|
Average
|
Ratio of
separation phase
|
||||
20
|
Group 1
|
0.6122
|
Group 5
|
0.7291
|
0.6707
|
0.6707±0.0585
|
|
25
|
Group 2
|
0.7826
|
Group 6
|
0.5128
|
0.6477
|
0.6477±0.1349
|
|
30
|
Group 3
|
0.7000
|
Group 7
|
0.7400
|
0.7200
|
0.7200±0.0200
|
|
35
|
Group 4
|
0.5800
|
Group 8
|
0.6667
|
0.6234
|
0.6234±0.0434
|
|
Discussion:
1.
What the
HLB values that produce a stable emulsion? Discuss.
From the experiment, test tube 1-3 are among
the most stable combination of emulsion as after 2 hours there are still no
phase seperation seen. Since the range of
HLB value to produce stable emulsion is 9.67-11.34, it can be said that
the emulsion is slightly lipophilic. So,
this emulsion is water in oil emulsion.This shows that test tube 8 is the most
unstable emulsion as it do not contain any surfactant to stabilize unstable
Gibbs energy. The purpose of surfactant added is to disperse oily phase in
aqueous phase (o/w) emulsion or aqueous phase in oily phase (w/o) emulsion
through the formation of micelles. The micelles will trap the hydrophobic drug
particles or the lipid globule to the micelles’ nucleus and surrounded by the
hydrophobic ‘tail’ of the surfactant molecule. While the hydrophilic phase, the
‘head’ of the surfactant molecule will be stay in the aqueous phase. Thus,
surfactant functions by mixing the two immiscible phase which are the aqueous
phase and oily phase. As a result, the phase of separation will occur
slowly. The usage of two emulsifying
agents will form a very stabilize emulsion.
2.
Compare
the physical nature or mineral oil emulsion formed and give comments. What is
Test Sudan III? Compare the colour spread in the emulsion formed and give
comments.
Ø There
are 8 emulsion produced in this experiment. All emulsion has different
proportion volume of Span 20 and Tween 80. Emulsion 4 has one bigger globule
which surrounded by small globule around it. The emulsion 5 and emulsion 6 have
a few large globules that arranged closely with small globule surround it.
While, emulsion 7 has quite a number of big globules compare to the other
emulsion. For emulsion 8, it just has a few droplets of particles as it physical nature since it only
contain mineral oil and distilled water.
Ø Sudan
III solution is oil or lipid soluble. So, it wills no mix with water. Thus, the
purpose of this test is to stain the sudanopilic substances usually lipids. The
oil will not be on top of the Sudan. The
Sudan III solution is red in colour and dissolves in oil. It will give red
colour to the oil globules when it is dissolved in oily phase. It is used to determine
the type of emulsion formed. We can classify the emulsion into oil-in-water
emulsion (o/w emulsion) or water-in-oil (w/o emulsion) through the Sudan test.
Ø For all
the emulsion, the reddish brown colour is spread in the emulsion. The
difference is the intensity of the colour is differing. As the HLB value
increase, the more hydrophilic it nature. So, the intensity of colour decrease
for emulsion 4 to 7 as the HLB value keeps increasing for the emulsion. In the
emulsion 8, the HLB value is 0. Thus, the property of the emulsion is
lipophilic. So, the Sudan III solution is mix well in the emulsion and give the
high intensity colour of reddish brown colour.
3.
Plot and
comment on it:
a) Graph
of mean viscosity of sample before and after temperature cycle against
different type and amount of mineral oil.
This graph shows the mean viscosity of sample before and after
temperature cycle against different types and amount of mineral oil. In this
graph, there are two manipulated variables which affect the results
(viscosities measured), including the amount and the types of oil added in the
emulsion. The viscosities measured before temperature cycles show that 35ml
Mineral oil emulsion has the greatest mean viscosity(730 cP), and this is
followed by 25ml Arachis oil emulsion(409.90 cP), 30ml of Olive oil
emulsion(136.65 cP) and 20ml Palm oil(100.00 cP). After the temperature cycles,
the viscosities measured show the similar rankings, except the greatest
viscosity is shown by 25ml Arachis oil emulsion (775.37 cP) in place of 35ml
Mineral oil emulsion (613.33 cP) which shows the 2nd rank in this
measurement.
Theoretically, the higher the content of oil in the emulsion, the
higher viscosity of the emulsion because the oil always has the higher
viscosity compared to water. However, practically, in this experiment, the
viscosities measured on the emulsions before and after temperature cycles show
the deviation from the theory stated, in which the 25ml Arachis oil emulsion
shows the greater viscosity compared to 30ml Olive oil before and after
temperature cycles. This may or may not be due to the second variable, which
are the types of oil used.
Theoretically, the higher the viscosity value (cP) of the type of
oil, the higher viscosity reading will be obtained from viscometer and this
factor may describe the deviation of the result obtained. Unfortunately, this
wish comes to nothing when we notice that the Arachis oil (40 cP) has the lower
viscosity compared to Olive oil (85 cP). Hence, the experiment carried out
should have the errors which cause the deviation to happen.
These errors include the incorrect measuring technique and improper
cleaning and washing of rotor of viscometer by distilled water, which lead to
inaccurate measurement of viscosities. Besides that, the errors occur during
preparation of emulsions, such as inaccurate weighing of excipients and active
ingredients, especially oil.
Gratifyingly, the measurement of viscosity in 20ml palm oil
emulsion and 35ml mineral oil emulsion show in accordance to the theory
provided, in which the palm oil shows the smallest value of viscosity while
mineral oil shows the greatest viscosity in general.
b)
Graph of viscosity difference (%) against different
amount of mineral oil.
Amount
of Oil Content (ml)
|
Average
viscosity (cP)
(×±SD)
|
Different
viscosity (%)
(×±SD)
|
|
Before
temperature cycle
|
After
temperature cycle
|
||
20ml
palm oil
|
100.00±14.14
|
116.67±22.51
|
16.67%
|
25ml arachis
oil
|
409.90±15.49
|
775.37±72.98
|
89.16%
|
30ml
olive oil
|
136.65±92.00
|
254.95±229.53
|
86.57%
|
35ml
mineral oil
|
730±121.66
|
613.33±343.78
|
-15.98%
|
This graph shows the
viscosity difference against different types and amount of mineral oil. This
graph describes the difference of viscosities which are measured before and
after temperature cycles. The temperature cycle is the cycle where the sample
is subjected to the temperature of 45°C for 30 minutes and followed by temperature of 4°C for 30 minutes. The purpose of condition the temperature
cycle is used to determine the possibility of phase inversion in the emulsion
system which indirectly determines the stability of an emulsion system by using
the same amount of acacia.
Theoretically, an o/w emulsion stabilized by
non-ionic emulsifying agent (acacia) can be subjected to phase inversion upon
heating because there is decrease in HLB value which lead to increase in
hydrophobicity. When the temperature reaches a stage that will equilibrate the
hydrophile-lipophile tendencies, it comes to the phase inversion to w/o
emulsion. In this stage, there should be increase in viscosity. This theory can
be used to explain the increase of difference in viscosity of 20ml Palm oil,
25ml of Arachis oil and 30ml Olive oil although there are other factors which
lead to the increase in viscosity in these three emulsions. These factors
include the formation and melting of small ice crystals take place during
temperature cycle disrupts the adsorbed layer of emulsifying agent at the
interface. Besides that, inaccuracy may also arise if contaminant is introduced
into emulsion.
Generally, the higher the oil content used in
the emulsion, the greater the possibility of phase inversion and greatest
viscosity difference because there is higher amount of disperse phase (oil),
leading the less stability. However, the Arachis oil shows the greatest
viscosity difference (89.16 %) although it is only 25ml in the emulsion. Also,
it shows a much higher viscosity difference compared to 20ml Palm oil (16.67 %)
although it contains only 25 ml of oil. This deviation may be due to the
inaccurate measurement errors. The errors also deemed to happen when the
negative difference in viscosity in 35ml mineral oil is obtained.
4.
Plot graph of separated phase ratio formed from the centrifugation
process versus the different amount of Turpentine Oil. Explain.
In the experiment, the emulsion is
separated into two different phase by centrifuge process. This is due to the centripetal acceleration force and a fast separation of
the emulsion will occurs. The ratio of the separation phase refers to the ratio
of the height of separated phase to the height of the original emulsion. The
larger the ratio of separation phase, the more unstable emulsion in the
experiment is.
In this experiment, the
volume of the oil is not much to focus but the overall emulsion formed with
certain amount of oil will be more stress on. From the graph above, it have
show that 35 ml of the mineral oil in the emulsion is the most stable emulsion
with the least separation while 25 ml of the mineral oil the least stable
emulsion with the most separation based on the ratio of separation phase.
Acacia is the important emulsifying
agent in the preparation of the emulsion. It will form a stable multi molecular film for the
designated amount of mineral oil and water. The fixed amount of acacia but
increasing volume of the mineral oil will caused the emulsion to become
unstable .This is due to the less capacity of the acacia to form a stable multi
molecular film . Thus, the increase the volume of the mineral oil should have
the greater separation of the emulsion.
In this experiment, technical
errors may be involved, either involving the equipment or human parallax error.
Phase separation comes along with a variety of pharmaceutical inaccuracies,
with the drug uniformity problem as the most significant one. When the emulsion
is separated, drug distribution within the emulsion is greatly affected, thus
the dosage administered by the patient would be inaccurate. Besides, it deeply
affects the stability of emulsion as well, possibly reducing patient compliance
at the same time.
What should we consider
most from the scene is that, phase separation comes along with a variety of
pharmaceutical inaccuracies, with the drug uniformity as the most significant
problem. When the emulsion is separated, or cracked, drug distribution within
the emulsion is greatly affected, thus the dosage administered by the patient
would be inaccurate. Besides, it deeply affects the stability of emulsion as
well, possibly reducing patient compliance at the same time.
5.
What are the functions of every substance used in this
emulsion preparation? How the different contents of substances can affect the
physical characteristics and stability in the formulation of an emulsion?
In the preparation of an
emulsion, there are some ingredients that are needed to be included as the main
proportion of the formulation.
They are oil
phase (mineral oil for example turpentin oil), aqueous phase (syrup, alcohol
and distilled water), emulsifying agent (acacia) and other substances such as
vanillin. They play their own role in making the emulsion stable and meet the
patient’s compliance.
Firstly
the oil phase of the emulsion, given by the mineral oil. Mineral oil functions
as the oil phase (internal phase or dispersed phase) in this oil in water (o/w)
emulsion. To produce stable oil in water emulsion, the oil content needs to be in
the range of 40% to 60%. It can provide moisture and emollient effects. It can
be considered natural for the purification process when compared with the
purification of other natural ingredients.
Syrup play the role as
sweetening agent as usually original emulsion will give a taste of oil, and may
not be accepted by patients. Thus it masks the taste of the emulsion. Besides
that, syrup increases the viscosity of the emulsion. The quantity and content
of the syrup have to be limited so that the emulsion produced will have a good
flow, can be poured easily from the container and do not form a viscous layer
on the side of the container.
The third important
ingredient is Vanillin. Vanillin acts as flavouring agent to improve the taste
of the emulsion so that it is more acceptable to the patients.
Other
than that, acacia also used as the emulsifying agent which can increase the
viscosity of the surface of the oil and aqueous phase. Furthermore, acacia is a
natural product and it is a suitable medium for the growth of microorganisms.
Hence, antimicrobial agent needs to be added to the emulsion to stabilize it.
Acacia will not decrease the surface tension.
Alcohol
functions as a preservative to prevent the growth of the microorganisms.
Distilled water on the other hand, act as the aqueous phase (external phase or continue
phase) in the oil in water (o/w) emulsion.
The different types of
mineral oil used in the preparation of emulsion will give rise to a different
physical characteristics and chemical stability in a formulation. Besides that,
the different compositions of mineral oil and distilled water used in the
preparation of emulsion will affect the types of emulsion produced, either oil
in water (o/w) emulsion or water in oil (w/o) emulsion. Oil in water emulsion
will be produced if the amount of distilled water used is in excess compared to
the oil used while water in oil emulsion is produced if the amount of oil used
is in excess. Hence, any change in the content of water or oil will results in
phase inversion.
Furthermore, the content of syrup can
affect the flow and physical characteristics of the emulsion formed. The
content of the syrup used must be controlled to avoid the problems with
flowability (rheology) and physical characteristics of the emulsion. Some of
the oils used have different colours and this will produce emulsion with
different colours. In addition, palm oil has antioxidant property and this can
improve the stability of the emulsion formed. The differences discussed above
will produce an emulsion with different physical characteristics and chemical
stability.
Conclusion:
The HLB value of the
surfactant used will affect the stability of the emulsion formed. Stability of
an emulsion depends both on the volume of the oil phase and aqueous phase,
together with the amount and capacity of the emulsifying agent to function in
the system. Homogenization causes the reduction in size of the globules in the
emulsion and the emulsion formed is more homogenous and smooth.
References:
- Aulton, M.E. Pharmaceutics: The science of dosage form design. 2002, Edinburgh:
Churchill Livingstone.
- http://dowhpc.custhelp.com/app/answers/detail/a_id/3277/~/surfactant-basics---definition-of-hlb,-and-how-it-applies-to-emulsions
good...
ReplyDeleteIf the HLB value is too high..it is not stable anyomre...so it should be within the suitable range for each type of oil
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