TITLE
Assessment of
the Effect of Different Ingredients towards the properties of an Emulsion
Formulation
OBJECTIVES
1. To investigate the effect of
HLB surfactant towards the stability of the emulsion.
2. To investigate the physical
effects and the level of stability on the emulsion formulation due to different
content of the emulsifying agent usage.
INTRODUCTION
Emulsion
is a two-phase system that is unstable thermodynamically. Emulsion is consist
of two immiscible liquid. One of the liquid is dispersed homogenously as
droplets in another liquid, which is known as the internal phase or the
dispersed phase. The liquid in which they are dispersed is known as external
phase or continuous phase. Emulsion can be divided into two types, which are
the oil in water emulsion and water in oil emulsion. Emulsions are highly
unstable system due to the presence of high surface tension between two phases.
The high surface tension will cause the globules to combine and revert back
into its original state after mixing. Thus, emulsifying agent is required to
stabilize the emulsion and prevent the globules from revert back into its
original position after mixing. Emulsifying agent can be divided into 3 types,
which are hydrophilic colloid, surface active agent or known as surfactant and
finely divided solids. There are a few
types of pharmaceutical emulsion, which are lotion, liniment, ointment, cream
and others.
There
is one method that can be used to produce a stable emulsion. It is called as
hydrophilic-lipophilic balance (HLB). Hydrophilic-lipophilic balance (HLB) can
be used to determine the suitable quantity and types of surfactant that can be
used to produce a stable emulsion. Each surfactant is assigned with a number in
the HLB scale. Number 1 surfactant has lipophilic property while number 20
surfactant has a hydrophilic property. These numbers are used to express the
size and strength of the polar region to the non-polar region in the molecules
of the surfactant. Usually, combination of two emulsifying agent is required to
produce a more stable emulsion. The HLB value for the combination of the
emulsifying agents can be determine using the formula below:
HLB value= (mass of surfactant 1) (HLB value of surfactant 1) + (mass
of surfactant 2) (HLB value of surfactant 2)
Mass of surfactant 1 + mass of surfactant 2
APPARATUS
AND MATERIALS
a)
Apparatus
8 test tubes
1 50 mL measuring cylinder
2 sets of Pasteur pipette and
droppers
Vortex
mixer
Measuring boat
1 set of mortar and pestle
Light microscope
Microscope slide
1 set of 5 mL pipette and bulb
1 50 mL beaker
1 15 mL Centrifuge tube
Coulter counter
Centrifuge machine
Viscometer
Water bath (45°C)
Fridge (4°C)
b)
Materials
Palm oil
Arachis oil
Olive oil
Mineral oil
Distilled water
Span 20
Tween 80
Sudan III (0.5%) solution
ISOTON III solution
c) Procedure
1. All
test tubes were labelled from number 1 until 8 each. A straight line was drawn
1 cm from the bottom of each test tube.
2. 4 mL
of the given test oil, as shown in Table 1 and 4 mL of distilled water, were
mixed in the test tube.
Table 1
Group
|
Test Oil
|
1, 5
|
Palm Oil
|
2, 6
|
Arachis Oil
|
3, 7
|
Olive Oil
|
4, 8
|
Mineral Oil
|
3.
Span 20 and Tween 80 were dropped into the mixture of oil and water. The number
of drops of Span 20 and Tween 80 were dropped into the mixture was according to
Table II. The test tube was sealed and placed on the Vortex mixer for 45 seconds. The time taken needed to reach the
interface of 1cm was recorded. The HLB value of each samples were determined.
Table II
No. of tubes
|
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 were added to 1g of emulsion that was formed
on a weighing boat and flattened. The dispersion of colour in the sample was
determined and compared under the light microscope. The shape and size of the
globules formed were drawn, explained and compared.
5.
A formulation of 50g of Mineral Oil Emulsion was prepared by using the wet gum
method and the following formula.
Mineral Oil
|
30mL (refer to Table III)
|
Acacia
|
6.25g
|
Syrup
|
5mL
|
Vanillin
|
2g
|
Alcohol
|
3mL
|
Distilled water (qs)
|
50mL
|
Table III
Emulsion
|
Group
|
Mineral oil (mL)
|
I
|
1, 2
|
20
|
II
|
3, 4
|
25
|
III
|
5, 6
|
30
|
IV
|
7, 8
|
35
|
6.
40g of the emulsion that was formed, was added into a 50 mL beaker and homogenization
process was carried out for 2 minutes by using a homogenizer.
7.
2g of the emulsion, which was taken before and after the homogenization,
respectively, was put on the weighing boat and labelled. A few drops of Sudan
III solution was added and flattened. The texture, consistency, degree of the
oily shape and dispersion of colour in the sample was determined and compared
under the light microscope.
8.
The viscosity of the emulsion, that was weighed 15g in the 50mL beaker, after
the homogenization process was determined by using viscometer that has been
calibrated with “Spindle” type LV-4. The sample then was exposed under the
temperature of 45°C (water bath) for 30 minutes and then to the temperature of
4°C (fridge) for 30 minutes. The viscosity of the emulsion was determined after
the exposure and after the emulsion reached the room temperature for about
10-15 minutes.
Readings
|
Viscosity (cP)
|
Average + SD
|
||
1
|
2
|
3
|
||
Before the temperature exposure
|
||||
After the temperature exposure
|
||||
Differences (%)
|
||||
9.
5g of the homogenized emulsion was added into the tube of a centrifuge and was
centrifuged at about 4500 rpm, for 10 minutes, at the temperature of 25°C. The
height of the interface formed was measured and the ratio of the height of the
interface was determined.
Heights (mm)
|
|
Interface
|
|
Original emulsion
|
|
Height ratio
|
RESULTS
Result of 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
|
HLB value
|
9.667
|
10.733
|
11.343
|
12.440
|
13.171
|
14.086
|
15.000
|
0.000
|
Phase separation time
(min)
|
167
|
169
|
170
|
25
|
44
|
50
|
17
|
10
|
Stability
|
++++
|
++++
|
++++
|
++
|
+++
|
+++
|
++
|
+
|
Calculation of HLB values:
Ø
HLB value for Span 20 = 8.6
Ø
HLB value for Tween 80 = 15.0
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)
|
Group 1
|
14
|
68
|
80
|
43
|
49
|
67
|
24
|
10
|
Group 5
|
Interphase
did not reach 1cm after 120 minutes.
|
16
|
30
|
39
|
16
|
7
|
|||
Average
|
-
|
-
|
-
|
29.5
|
39.5
|
53
|
20
|
8.5
|
|
Stability
|
++++
|
++++
|
++++
|
++
|
++
|
+++
|
++
|
+
|
|
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)
|
Group 2
|
12
|
76
|
82
|
27
|
40
|
55
|
19
|
9
|
Group 6
|
167
|
169
|
170
|
25
|
44
|
50
|
17
|
10
|
|
Average
|
89.5
|
122.5
|
126
|
26
|
42
|
52.5
|
18
|
9.5
|
|
Stability
|
+++
|
+++
|
+++
|
+
|
++
|
++
|
+
|
+
|
|
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)
|
Group 3
|
80
|
Interphase
did not reach 1cm after 120 minutes.
|
70
|
95
|
100
|
25
|
||
Group 7
|
Interphase
did not reach 1cm after 120 minutes.
|
14
|
Interphase
did not reach 1cm after 120 minutes.
|
69
|
Interphase
did not reach 1cm after 120 minutes.
|
55
|
10
|
||
Average
|
-
|
-
|
-
|
-
|
69.5
|
-
|
77.5
|
17.5
|
|
Stability
|
++++
|
++++
|
++++
|
++++
|
+++
|
++++
|
+++
|
+
|
|
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)
|
Group 4
|
Interphase
did not reach 1cm after 120 minutes.
|
92
|
118
|
84
|
68
|
74
|
17
|
3
|
Group 8
|
Interphase
did not reach 1cm after 120 minutes.
|
50
|
24
|
28
|
29
|
15
|
18
|
0.5
|
|
Average
|
-
|
71
|
71
|
56
|
48.5
|
44.5
|
17.5
|
1.75
|
|
Stability
|
+++++
|
++++
|
++
|
+++
|
+++
|
+
|
+
|
-
|
|
Magnification (40×10)
|
Physical appearance
|
Colour distribution
|
TEST TUBE 1
 |
Globules
are colourless and the outline is red.
Size
of globules are big and small
Shape
of globules are round |
Sudan
III colour dispersed in the emulsion. The emulsion stained light orange.
|
TEST TUBE 2
 |
Globules
are colourless and the outline is red.
Shape
of globules are very small
Shape
of globules are round |
Sudan
III colour dispersed in the emulsion. The emulsion stained light orange.
|
TEST TUBE 3
 |
Globules
are colourless and the outline is red.
Some
globules are big and some are very small. Maybe due to errors.
Shape
of globules are round |
Sudan
III colour dispersed in the emulsion. The emulsion stained light orange.
|
TEST TUBE 4
 |
Globules
are colourless and the outline is red.
Some
globules are big and some are small
Shape
of globules are round |
Sudan
III colour dispersed in the emulsion. The emulsion stained light orange.
|
TEST TUBE 5
 |
Globules
are colourless and the outline is red.
The
globules are very small
Very
closely packed together
Shape
of globules are round |
Sudan
III colour dispersed in the emulsion. The emulsion stained light orange.
|
TEST TUBE 6
 |
Globules
are colourless and the outline is red.
The
globules are big and small
Shape
of globules are round |
Sudan
III colour dispersed in the emulsion. The emulsion stained light orange.
|
TEST TUBE 7
 |
Globules
are colourless and the outline is red.
Some
globules are very large and some are small
The
shape are round |
Sudan
III colour dispersed in the emulsion. The emulsion stained light orange.
|
TEST TUBE 8
 |
Globules
are colourless and the outline is red.
The
globules are very big
The
shape are not round and Irregular in shape
Globules
are very far apart from each other |
Sudan
III does not disperse in the emulsion, globules of Sudan red form on surface
of emulsion.
|
Viscosity
Reading
|
Viscosity(cP)
|
Average + SD
|
||
1
|
2
|
3
|
||
Before
water bath n freezing
|
3030
|
3060
|
3090
|
3060 + 30.00
|
After
water bath and freezing
|
6080
|
6060
|
6010
|
6050 + 36.06
|
Difference (0/0)
|
97.71%
|
|||
Height (Volume of mineral oil – 30 ml)
Height (mm)
|
|
Interface (mm)
|
34.00
|
Initial Emulsion (mm)
|
50.00
|
Height ratio
|
3.4 : 5
|
Discussion:
1. What are the values of HLB that produce stable emulsion? Discuss.
The
HLB of an emulsifier is an expression of its Hydrophile-Lipophile Balance,
example the balance of the size and strength of the hydrophilic (water-loving
or polar) and the lipophilic (oil-loving or non-polar) groups of the
emulsifier. All emulsifiers consist of a molecule that combines
both hydrophilic and lipophilic groups. An emulsifier that is lipophilic in
character is assigned a low HLB number
(below 9.0), and one that is hydrophilic is assigned a high HLB number (above
11.0). Those in the range of 9-11 are
intermediate. When two or more emulsifiers are blended, the
resulting HLB of the blend is easily calculated. For example, suppose you want
to determine the HLB value of a blend comprising 70% of TWEEN 80 (HLB = 15) and
30% Of SPAN 80 (HLB = 4-3).
The
calculation would be:
TWEEN
80 70% X 15.0 = 10.5
SPAN
80 30% X 4.3 = 1.3
HLB
of blend = 11.8
Moreover,
the HLB of an emulsifier or blend of emulsifiers is an excellent indication of
what the emulsifier system will do, that is, whether it will make an oil-in-water
(O/W) emulsion or a W/O emulsion, or act as a solubilizer for some oil. The HLB
of an emulsifier class or blend is also an indication of the efficiency of
chemically-related emulsifiers or of a blended pair of
emulsifiers for performing any given emulsifier task.
Besides,
the HLB of an emulsifier is related to its solubility. Thus, an emulsifier
having a low HLB will tend to be oil-soluble, and one having a high HLB will
tend to be water-soluble, although two emulsifiers may have the same HLB and
yet exhibit quite different solubility characteristics. HLB Range from 4 to 6
will produce water-in-oil emulsions which are stable. On the other hand, in
order to produce oil-in-water emulsions which are stable, emulsifiers with HLB
values ranging from 8 to 18 should be used. For the HLB value between 7-9, emulsifying
agents normally act as wetting agent, while between 13-15, they act as
detergents, and value of 15-16, they are become solubilizing agent.
Based on the
experiment, surfactants used in this experiment are Span 20 and Tween 80.
Sorbitan monostearate is an ester of sorbitan (a sorbitol derivative)
and stearic
acid and is sometimes referred to as a synthetic
wax.It is primarily used as an emulsifier to
keep water and oils mixed. Sorbitan monostearate is used in the manufacture of
food and healthcare products and is a non-ionic surfactant with
emulsifying, dispersing, and wetting properties[.It is also employed
to create synthetic fibers, metal machining fluid, and brighteners in the
leather industry, and as an emulsifier in coatings, pesticides,
and various applications in the plastics, food and cosmetics industries.
Sorbitans are also known as "Spans". Span 20 has HLB value of 8.6 while tween 80
has HLB value of 15. While for tween 80 which also known as Polysorbate is
a non-ionic surfactant and emulsifier derived
from polyethoxylated sorbitan and oleic
acid, and is often used in foods. Polysorbate 80 is a
viscous, water-soluble yellow liquid. The hydrophilic groups
in this compound are polyethers also
known as polyoxyethylene groups which are polymers of ethylene oxide.
In the nomenclature of polysorbates, the numeric designation following
polysorbate refers to the lipophilic group,
in this case the oleic acid.Polysorbate 80 is often used in food and other
products as an emulsifier.
According
to the results, the HLB value of tube 7 is the highest followed by tube
6,5,4,3,2 and 1. For test tube 1, the
time taken for the phase to separate is 167 which is more than 120 minutes,
same as tube 2 (169>120min) and tube 3 (170>120min). We can determine the
stability of an emulsion easily from the separation phase time. Emulsion which
has the longest separation phase time is the most stable emulsion. This is
because a stable emulsion contains
emulsifying agents added that able to mix and stabilize the two phases well for
a very long time. Thus this shows that the emulsion in test tube 1,2 and 3 are
much more stable compare to others due to the presence of more drops of
emulsifying agent. The longer time of phase separation for test tube 1 is due
to hydrophobicity of span 20. Test tube 1 have a higher concentration of span
20, it have a longer separation time
compared to the others test tube, it have the higher hydrophobicity so it can
be conclude that emulsion in test tube 1,2 and 3 are more stable. In addition,
the time taken for test tube 4 is 25 minutes, followed by test tube 5 (44min)
and 6 (50min). they are less stacble compare to test tube 1, 2 and 3. In test
tube 7 where there is only Tween 80, emulsion that is formed is not stable as
it contains shorter separation phase time (17minutes). This shows that a
combination of surfactants can give much better emulsifying effect than they
are used alone. Besides, a very short time (10 minutes) is required to separate
the two phases in test tube 8 because there is totally no emulsifying agent added.
In comparison with other group that use the same
oil as our group, the time taken for test tube 1, 2 and 3 are quite same, in
which the time taken for interphase to reach 1 cm is more than 120 minutes. For
test tube 4,5 and 6 the time taken for interphase to reach 1 cm for other group
is a little bit faster than our group. However, the time for interphase to reach 1cm is still shorter than test tube
1,2 and 3 so the conclusion that we both group make is the same.
In order to observe the dispersion of colour of the
sample, few drops of Sudan III solution is dropped into 1g of the emulsion. The
color in tube 1 is the most difficult to spreads compare to test tube 2, 3, 4,
5, 6, 7 and 8. The viscosity of the emulsion in test tube 1 is the most
viscous, thus when the Sudan III solution is dropped into the emulsion, the
solution cannot break through the particle in the emulsion. This is because
test tube 1 with more drops of span 20 have more hydrophobic character and
hence, this leads to an increase in viscosity and a greater difficulty for
colour to spread. While colour in tube 7 having the easiest to spread and it
does not need to be stirred before it can mixed with the emulsion. This showed
that the viscosity in test tube 7 is not as viscous as in test tube 1. The
Sudan III easy to break through as the distant between particles is quite far
and the size particle (droplet) also bigger.
2. Compare the
physical appearance of the mineral oil emulsions produced and give your
comments. What is Sudan III test? Compare the dispersion of colour in the
emulsions produced and give your comments.
Group 1
and 5 (20 mL of palm oil)
Description
|
|
Before homogenization
|
Physical
appearance: less milky, not consistent, more
greasy
Globules: more globules, not uniform with big in size
Color
dispersion: uneven dispersed, less red spot
Viscosity: less viscous
|
After homogenization
|
Physical
appearance: milky, consistent, less greasy
Globules:less globules, uniform with small in size
Color
dispersion: evenly dispersed, more red spot
Viscosity: more viscous
|
Group 2 and 6 (25 mL of arachis oil)
Description
|
|
Before homogenization
|
Physical
appearance: not evenly and milky, not
consistent, more greasy,
Globules:
more globules, big and uneven
Color
dispersion: unevenly dispersed, less red spot
Viscosity: less viscous
|
After homogenization
|
Physical
appearance: evenly and yellowish, consistent,
less greasy
Globules: less globules, small and evenly distribution
Color
dispersion: evenly dispersed, more red spot
Viscosity: more viscous
|
Group 3 and 7 (30 mL of olive oil)
Description
|
|
Before homogenization
|
Physical
appearance: coarse and not homogenous, not
consistent, more greasy
Globules: more globules, large globules with different size
Color
dispersion: unevenly dispersed, less red spot
Viscosity: less viscous
|
After homogenization
|
Physical
appearance: smooth and homogenous, consistent, less
greasy
Globules:
Less globules, smaller and uniform
Color
dispersion: evenly dispersed, more red spot
Viscosity: more viscous
|
Group 4 and 8 (35 mL of Mineral oil)
Description
|
|
Before homogenization
|
Physical
appearance: smooth and cloudy, not consistent, very
greasy
Globules:More globules, not uniform with both big and small size
Color
dispersion: unevenly dispersed, less red spot
Viscosity: less viscous
|
After homogenization
|
Physical
appearance: smooth and milky, consistent, less
greasy
Globules:Less globules, uniform size
Color
dispersion: evenly dispersed, more red spot
Viscosity: more viscous
|
Homogenization
is the act of making something homogeneous or uniform in composition. It makes
the emulsion more stable and consistent with less occurrence of phase inversion.
Before homogenization, the physical appearances of the emulsions are less
milky, greasy, less viscosity. The emulsions are very unstable and tend to
undergo phase inversion. When it is being observed under light microscope the
red globules appear in different sizes and are not uniform in size.
After
homogenization, the emulsions become more stable. The physical appearances of
the emulsions are smooth and milky, consistent, less greasy and more viscous.
When it is being observed under light microscope the red globules appear in
uniform with small size and evenly distributed. The shape of the globules is
same before and after the homogenization which is spherical globules.
Sudan
III solution is a fat-soluble dye that is used in Sudan III test. It does not
mix with water. It is used for staining the oily globules. Sudan III has a red
color solution that will dissolve in the oily phase to give a red globules
color. The aqueous globules will not be stained, thus, it appears as colorless.
Therefore, Sudan III test could be used to determine whether this emulsion is
oil in water (o/w) or water in oil (w/o) emulsion. Oil in water (o/w) emulsion
has red globules on colorless background, while water in oil (w/o) emulsion has
colorless globules in red background.
The color dispersion before homogenization is
uneven. Therefore, the emulsion formed before homogenization is water in oil
emulsion. However, after homogenization, the red stain is even. Red globules
have been seen in uniform dispersion under colorless background. Hence, oil in
water emulsion is formed after homogenization.
3. Plot and give
comments on:
a) The graph of the
viscosity of the sample before and after the temperature cycle against the
different amount of mineral oil content.
b) The graph of the
difference in viscosity (%) against the different amount of mineral oil
content.
Mineral oil contents
(mL)
|
Viscosity (cP)
(x ± SD)
|
Viscocity difference
(%)
(x±SD)
|
|
Before temperature cycle
|
After temperature cycle
|
||
20
|
18.93 + 2.0422
|
19.30 ± 3.9800
|
1.95±64.36
|
25
|
1360±519.81
|
1180±61.64
|
14.17±157.60
|
30
|
3020± 96.44
|
6250±984.53
|
69.69±164.31
|
35
|
3290±17.32
|
13010±1326.91
|
119.26±194.85
|
Some of emulsions become unstable when they are frozen
and thawed. A good emulsion can adapt to extreme high and low temperature.
Temperature is the one of the factor that can change rheological behaviour.
When rheological behaviour of an emulsion matrix changes, that its Newton’s
flow region can be reduced, that the apparent viscosity will increase and show
its yield characteristics during the shelf life. Instability of emulsion caused
by freezing is due to physicochemical changes such as formation of ice crystals
in the aqueous phase forces the oil droplets close together. Freezing also
cause ionic strength in the aqueous phase increases due to the ice
crystallization and electrostatic repulsion between droplets are screened which
promote droplet coalescence. The disruption of the interfacial membranes of oil
droplets during freezing cause oil droplets are more susceptible to coalescence
during thawing.
The stability of an emulsion during freeze-thaw is also
influenced by the type and concentration of the fat phase. Highly concentrated
emulsion are more susceptible to destabilization because of greater stress on
the dispersed phase during frozen state. From the graph, we can prove that
highly concentrated of emulsion containing mineral oil 30ml and 35ml increased
in viscosity gradually after temperature cycle. This will not good for emulsion
stability as emulsion will throughout the shelf life under various condition
and temperature.
Graph above shows the
differences in viscosity versus amount of mineral oil.Amount of oil in
emulsion affected viscosity difference (%). From 20ml to 25ml of mineral oil in
emulsion, the viscosity difference (%) increases slowly. But after 25ml to 35ml
of mineral oil in emulsion, the viscosity difference (%) increases rapidly. In
theory, an increase in the amount of mineral oil will show an increase in
viscosity difference. This is because mineral oil is the dispersed phase. If
the dispersed phase increased, viscosity of the emulsion should be increased. High oil concentration
often led to an increase in particle size and viscosity. Emulsion prepared
using 20ml-25ml oil exhibited good appearance with a homogeneous texture,
smoothness and colorless. However, emulsion using 25ml-35ml was more less
texture and smoothness due to cracking and separation into two phases.
4. Plot the graph of
the ratio of the separation phase after centrifugation process against the
different contents of mineral oil. Give your comments.
Mineral Oil (ml)
|
Group
|
Separation phase (mm)
|
Initial emulsion (mm)
|
Ratio of Separation Phase
|
Average Ratio
(Average ± SD)
|
Emulsion I (20mL)
|
1
|
1.8
|
4.4
|
0.41
|
0.49 ± 0.08
|
2
|
2.6
|
4.6
|
0.57
|
||
Emulsion II (25mL)
|
3
|
3.4
|
5.0
|
0.68
|
0.61 ± 0.07
|
4
|
2.7
|
5
|
0.54
|
||
Emulsion III (30mL)
|
5
|
1.5
|
7
|
0.21
|
0.375 ± 0.165
|
6
|
27
|
50
|
0.54
|
||
Emulsion IV (35mL)
|
7
|
12.6
|
43
|
0.29
|
0.295 ± 0.005
|
8
|
14
|
46
|
0.30
|
Phase separation ratio is used to indicate the stability of an
emulsion. A high ratio of phase separation will result in unstable emulsion and
form two distinct phases. The presence of two distinct phases shows that the
emulsion possesses inadequate stability. Centrifuges accelerate the phase
separation processes in the emulsion by enhancing the specific gravity
differences. The concept of the phase separation by centrifugal is based on
density difference of the oil and water phase in an emulsion, either oil-in-water
emulsion or water-in-oil emulsion. After the process, phase separation will
occur where the water and oil phase will separate into two significant layers.
Since the oil has lower density than water, it will rise upward and appear at
the upper layer while water is at the bottom layer. There is not much
difference between densities of oil being used. Hence, the type of oil did not
give much effect to the result. According to the theory, the separated phase
ratio will also increase follow by the increasing amount of the oil. This is
because the amount of oil added in emulsion is beyond the amount of oil
required in which a stable emulsion can be formed. Thus, phase separation will
occur at a faster rate. However, according to the graph above, phase separation
ratio decreases when the amount of oil increases. This shows that the result
did not follow the theory exactly. This is because some errors occurred during
the experiment. For instance, the presence of contaminant in the emulsion has
influence on the accuracy of the result. Besides that, the incorrect amount of
oil also affects the accuracy of results being obtained. Parallax error may
also occur when measuring the height of separation phase. There is also
possibility that some groups measured the separation phase by using height of
water phase instead of oil phase. Therefore, many problems arise during the
experiment due to the variety of workforce and inaccurate measurements of
readings. Ingredient that is use in this emulsion is Acacia, Syrup, Vanillin,
Alcohol, Olive oil and distilled water. Olive oil and distilled water is used
as a basic ingredient in the making of emulsion. The distilled water used as
vehicle and can function as aqueous phase (continuous phase) in oil-in-water
emulsion whereas the oil as oil phase in oil in water emulsion. Acacia are
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 lower the surface tension of water molecule and
provide an evenly mixing between oil and water molecule. This make the emulsion
more stable. However, it promotes the growth of microorganism, hence
antimicrobial agents should be added to prevent the growth of the
microorganisms. The antimicrobial preservative use is alcohol. Different type
of oil will have different viscosity. The more viscous the oil , the more
stable the emulsion. Different composition of oil and water will determine the
type of emulsion either oil in water or water in oil emulsion. If there is too
much oily phase in an o/w emulsion, the emulsion will become very unstable, and
phase inversion will occur where it is converted into w/o emulsion. Hence,
suitable emulsifying agents with suitable HLB value should be selected in order
to produce a stable emulsion. Different proportion of emulsifying agents will
give different stability and emulsifying effect. Sometimes, a combination of
the surfactant can be used to improve the stability of the emulsion. Unsuitable
surfactants will produces emulsions with different physical properties such as
globule size, texture, consistency, oily phase dispersion, etc. These may
affect the therapeutic effects of the emulsion. The use of different type of
mineral oil will affect the physical characteristics and chemical stability of
emulsion. For example, palm oil has anti-oxidant properties which increase the
chemical stability of the emulsion. This type of emulsion will be less prone to
oxidation than using other types of oil.
5. What are the
functions of every material used in the preparation of this emulsion? How do
the different content of materials can affect the physical characteristics and
stability in the formulation of an emulsion?
The substances that are used in this emulsion
preparation is mineral oil, acacia, syrup, vanillin, alcohol and distilled
water. Acacia is a type of emulsifying agent used to emulsify two immiscible
liquids to form an emulsion. Acacia helps to prevent coalescence of the
globules of the dispersed phase by reducing the surface tension between two
phases and helps to form a stable interfacial film. Acacia is highly resistant
towards the rupture of the interfacial film. However, acacia is made up of
natural resources which is prone to microbial growth. Alcohol is added to the
emulsion to act as an antimicrobial agent. Alcohol functions as to prevent
microbial growth in the emulsion, due to the presence of water, syrup and
acacia. Alcohol has relatively low effect on long term stability of the
emulsion. This is due to the presence of Ostwald ripening. Distilled water is
used as a vehicle and plays a role as an aqueous phase in the oil-in-water
emulsion. Vanillin is acted as a sweetening agent. Vanillin helps to aid with
patients compliance as well as to mask the unpleasant taste of the emulsion.
Syrup plays a role as a flavouring agent that functions to mask the unpleasant
taste of the mineral oil and increases patience compliance. This is because the
sugar contains a high concentration of sucrose. The syrup is used to increase
the viscosity of the emulsion. The amount of syrup will determine the ability
and the efficiency of the emulsion to flow. Mineral oil plays a role as an oil
phase in this oil in water emulsion. Mineral oil is the dispersed phase in this
emulsion. However, the amount of mineral oil added to the emulsion is crucial
to determine whether the emulsion is oil in water or water in oil. If there is
too much mineral oil added to the oil in water emulsion, the emulsion becomes
unstable and phase inversion will occur. The emulsion will become water in oil
emulsion. Different oil has different viscosity. The high level of viscosity
will stabilize the emulsion.
Conclusion:
The
effect of HLB of surfactant on emulsion stability and physical effects was
determined. A suitable amount of emulsifying agent should be added into the
emulsion. This is to achieve HLB value required by the oily phase in order to
produce a stabile emulsion. The stability of the emulsion formulation due to
usage of different emulsifier agents was identified.
References :
1. Aulton,
M.E. Collet, D.M. Pharmaceutical Practice. Edinburgh: Churchill Livingstone.
2.
Salager, J.L, Emulsion Properties and Related Know-how to Attain Them,
Pharmaceutical Emulsions and
Suspensions, 2000, Marcel Dekker Inc.
3.
Kalur, G. C, Frounfelker, B. D, Cipriano, B. H, Norman, A.L, Raghavan, S.
R,
ViscosityIncrease with Temperature in Cationic
Surfactant Solutions Due to the
Growth of Wormlike Micelles, 2005, American Chemical
Society.
4. http://intranet.tdmu.edu.ua/data/kafedra/internal/pharma_3/classes_stud/АПТЕЧНА%20ТЕХНОЛОГІЯ%20ЛІКАРСЬКИХ%20ЗАСОБІВ/фармацевтичний%20факультет/3%20курс/Фармація/english/Emulsions.htm
5. http://pharmlabs.unc.edu/labs/emulsions/intro.htm
6. http://www.wasanlab.com/pharm/emulsion.html
7. http://www.lumamericas.com/glossary_emulsion_suspension_dispersion_colloid_chemistry.html
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