Basics of emulsion.pdf

Emulsion

1. PREPARED BY:
Bhargavi Mistry
[M Pharm (Pharmaceutics)]
BASICS OF
EMULSION

2. LIST OF CONTENT
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1) Introduction 3
2) Types of emulsions 5
3)
Pharmaceutical applications of
emulsion
10
4)Tests for identification of emulsion 13
5) Theories of emulsion 20
6) Questions 36
7) References 37

3. INTRODUCTION
ØEmulsion is the biphasic (heterogeneous system) liquid dosage form, in which
both the phases( the disperse phase & dispersion phase) are liquids.
ØThey are thermodynamically unstable systems consisting of at least two immiscible
phases, in which one phase is dispersed as globules in the other liquid phases with
the help of an emulsifying agent.
1)Dispersed phase (Internal phase):
Ø The phase which is in the fine globules form is called the dispersed phase or
internal phase.
2) Dispersion medium (external phase):
Ø The phase in which fine globules are dispersed is called the dispersion medium or
external phase.
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4. ØAny of the two phases may vary in consistency from mobile liquid to the semisolid
range.
ØThus emulsified system includes mixtures of relatively low viscosity to the creams
of high viscosity.
ØBased on the constituents and the intended application, liquid emulsions may be
employed orally, topically, or parenterally, and semisolid emulsions topically.
ØThe globule size of the dispersed phase varies from 0.01 µm to 100 µm.
ØEXAMPLES: Milk
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5. TYPES OF EMULSIONS
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0101
Water-in-oil
(W/O)
Oil-in-water
(O/W)
Complex emulsions
(multiple emulsions)
0102
0103

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7. ØA water-in-oil emulsion is a type of emulsion in which the continuous phase is
usually hydrophobic materials such as oil and the dispersed phase is water.
ØThe W/O emulsions contain three substances such as; a solvent, a surfactant, and
water.
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01Water-in-oil emulsions

8. ØAn oil-in-water emulsion is an emulsion in which the oil exists as the dispersed
phase and water as the dispersion medium or continuous phase.
ØThe emulsions of W/O are more common than O/W, thus O/W emulsions are often
pointed as reverse emulsions.
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02Oil-in-water emulsions

9. ØMultiple emulsions such as water-in-oil-in-water (W/O/W) and oil-in-water-in-oil
(O/W/O).
ØThe Multiple emulsions are more complex and contain very small droplets
suspended in larger droplets that are also dispersed in a continuous phase.
ØMultiple emulsions are stabilized using a combination of hydrophilic and
hydrophobic surfactants.
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03Complex emulsions (multiple emulsions)

10. PHARMACEUTICAL APPLICATIONS
OF EMULSIONS
ØEmulsification enables the preparation of relatively stable and homogeneous
mixtures of two immiscible liquids.
ØIt permits the administration of a liquid drug in the form of minute globules rather
than in bulk.
ØFor orally administered emulsions, the O/W type permits palatable
administration of distasteful oil by dispersing it in a sweetened, flavored aqueous
vehicle.
ØThe reduced particle size of the oil globules may render the oil more digestible
and more readily absorbed or, if that is not the intent, more effective in its task,
for example, the increased efficacy of mineral oil as a cathartic when emulsified.
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11. ØIt gives the opportunity to administer the oil-soluble drug in fine globules for its
depot action.
ØEmulsions to be applied to the skin may be o/w or w/o, depending upon the
requirement.
ØMedicaments that are irritating to the skin become less irritating if present in the
internal phase.
ØOn the unbroken skin, a w/o emulsion can usually be applied more evenly because
the skin is covered with a thin film of sebum, and this surface is more readily
wetted by oil than by water.
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12. ØIf water-washable topical preparation is required, O/W types of emulsion are
suitable.
ØEmulsification is used in aerosol products to produce foams. The propellant that
forms the dispersed liquid phase within the container vaporizes when the emulsion
is discharged from the container. This results in the rapid formation of foam.
ØIntravenous emulsions are prepared to contain fats, oils, carbohydrates, vitamins,
and other nutrients to be administered as replacement therapy for debilitated
patients.
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13. ØThere are five tests for the identification of emulsions:
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TESTS FOR IDENTIFICATION
OF EMULSION
01
02
03
04
05
Dilution test
Dye solubility
test
Fluorescence
test
Direction of
creaming test
Conductivity
test

14. ØThis test is based on the fact that an emulsion can be diluted only with external
phase.
ØO/W – diluted with water and remains stable but not with oil.
ØW/O – diluted with oil and remains stable but not with water.
ØThis test is useful for liquid emulsion only.
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01Dilution test

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O/W emulsion W/O emulsion
H
2O
O/W
emulsion
Stable
Oil
O/W
emulsion
Not
homogenous
Oil
Oil
W/O
emulsion
Stable
H
2O
W/O
emulsion
Not
homogenous
H
2O

16. ØThis test is based on the fact that the
dye is dispersed uniformly throughout
an emulsion if the dye is soluble in the
external phase.
ØWater soluble dye (Amaranth) tints
colored only O/W emulsion but not
W/O.
ØWhile Oil soluble dye (Scarlet red)
gives color to W/O emulsion but not
O/W.
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02Dye solubility test
Oil
globules
O/W emulsion
W/O emulsion
Water
soluble dye
Oil soluble
dye
Water
globules
Water
soluble dye
Oil soluble
dye

17. ØMany oils exhibit fluorescence when
expose to UV light.
ØWhen the drop of emulsion examines
under the fluorescence light:
O/W - exhibit dot pattern
W/O - Entire field fluoresce
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03Fluorescence test O/W emulsion
W/O emulsion
Oil droplets
fluoresce
Oily background
fluoresce

18. ØThis test is based on the fact that water or aqueous solutions conduct an electric
current while oils do not.
Ø O/W emulsions conduct electric current while W/O do not.
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04Conductivity test
O/W emulsion W/O emulsion
SWITCH ON
BULB
LIGHTEN
SWITCH ON
BULB NOT
LIGHTEN

19. ØCreaming is the process of sedimentation
of the dispersed droplets (either upward
or downward) due to the difference in
densities of the internal and external
phases.
ØThe density of oil/lipid phases is less
than that of the aqueous phase.
O/W emulsion: upward creaming
W/O emulsion: downward creaming
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05Direction of creaming test
O/W emulsion
Upward
creaming
W/O emulsion
Downward
creaming

20. ØTo understand the emulsion system and emulsification, a number of theories have
been given.
ØThe theories of emulsion are as follows:
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THEORY OF EMULSION
01
02
03
04
05
Surface tension theory
Oriented wedge theory
Plastic or interfacial theory
Charge repulsion theory
Steric repulsion theory

21. ØDrop of liquid which is always spherical in shape due to its internal forces that
tend to promote the association of the molecules of the substances to resist the
distortion of the drop into a less spherical form.
Air Drop of water
Figure: Formation of spherical drop,
resisting distortion into less spherical form
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01Surface tension theory

22. ØWhen two or more drops of the same liquid come into contact with one another,
they will join or coalesce, making one larger drop have a lesser surface area than
the total surface area of individual drops.
ØThis tendency of liquids may be measured quantitatively, and when the
surrounding of the liquid is air, it is called surface tension of liquids.
ØWhen the liquid is in contact with a second liquid in which it is insoluble and
immiscible, the force that causes each liquid to resist breaking up into smaller
particles is called interfacial tension.
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23. Come in contact
with one another
Water drops
(Total surface area
of drops is large)
One large drop
(Less surface area)
Air
Surface tension
Figure: Coalescence of water drops
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24. Drops of immiscible liquids
(O- Oil, W- Water)
Interfacial tension
O W O W
O W O O
O W O W
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25. ØThere are some substances that can promote the breaking of large globules by
lowering the resistance which results in the formation of smaller drops of liquid.
ØThese tension-lowering substances are called surfactants, surface-acting agents, or
wetting agents.
ØThese surfactants will lower the interfacial tension of two immiscible liquids,
reduce the repellent force between liquids and reduce the attraction of liquid for its
own molecule.
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26. ØThis theory explains the emulsion formation on the basis of the selective solubility
of surfactant (emulsifying agent).
ØSurfactant curved around a droplet of the internal phase of the emulsion.
ØIf a system contains two immiscible liquids and an emulsifying agent is added to
that system, the emulsifying agent is embedded more deeply in one of the phases
in which it is more soluble than other phases.
ØThe orientation, wedge shape arrangement of the molecules of emulsifying agent,
will form surround either oil globules or water globules.
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02Oriented wedge theory

27. Figure: Orientation of emulsifying agent (more
hydrophilic) surrounding oil and water drops
O/W emulsion W/O emulsion not
possible
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Oil Water
Polar
Nonpolar

28. ØEmulsifying agents having greater hydrophilic character than hydrophobic
character will promote an oil-in-water emulsion.
ØWhile agents having greater hydrophobic character than hydrophilic character will
form a water-in-oil emulsion.
ØIn other words, the phase in which the Emulsifying agent is more soluble will
become the continuous or external phase of the emulsion.
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29. Figure: Orientation of emulsifying agent (more
hydrophobic) surrounding oil and water drops
O/W emulsion not
possible
W/O emulsion
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WaterOil
Nonpolar
Polar

30. ØAccording to this theory, the emulsifying agent is deposited upon the surface of
the individual droplets of the dispersed phase in the form of a thin plastic film.
ØThis film prevents the contact and coalescence of the dispersed liquid.
ØThe stability of the emulsified system depends upon the magnitude of the
robustness of the film formed over the surface of globules.
ØThe tougher and more pliable the film, the greater the stability of the emulsion.
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03Plastic or interfacial theory

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Figure: Formation of film on oil droplets
a) Stable b) Fairly stable c) Poorly stable

32. ØThis theory of emulsions explains that the fine globules of the dispersed phase are
separated due to the repulsive forces developed as a result of the nature of the
emulsifying agent or by adsorbing ions from the dispersion medium.
Ø The charge develop on the surface of oil globules is enough to cause repulsion
between the droplets which acts as an electric barrier to prevent the coalescence of
the oil droplets and allow the oil phase to remain in droplet form, uniformity
dispersed in the continuous water phase.
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04Charge repulsion theory

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Oil
++
+
+
+
+
+
+
+
+
+
+
+
+
++++
+
+
+
+
+
+
+
+
+
+
+
+
+
Oil
++
+
+
+
+
+
+
+
+
+
+
+
+
++++
+
+
+
+
+
+
+
+
+
+
+
+
+
Repulsion
Figure: Development of repulsion due to adsorption of
cationic emulsifying agent on the oil globules

34. ØThis theory says that the repulsion develops between the water droplets due to the
long hydrocarbon chains of emulsifying agent which has been adsorbed on their
surface.
ØThis repulsion is called steric repulsion, preventing the contact or coalescence of
water droplets.
ØThis theory explains the process of emulsification in the W/O type of emulsion.
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05Steric repulsion theory

35. Prepared by: Bhargavi Mistry 35
Figure: Development of steric repulsion due to long
hydrocarbon chain of emulsifying agent between water droplets.
W
W
W
Oil
Long hydrocarbon
chain

36. 1) What is an emulsion? Discuss Pharmaceutical applications of emulsion in brief.
2) Explain in detail various identification tests for emulsion.
3) Enlist different theories of emulsion. Explain any two in detail.
4) What are the different types of emulsion? Explain.
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QUESTIONS

37. 1)H. C Ansel, Pharmaceutical dosage forms and drug delivery systems, 10
th edition,
Lippincott Williams & Wilkins, Page no. 465,466
2)Dr. A.K. Seth, A textbook of pharmaceutics, 2
nd edition 2022, Pee Vee publication,
Page no. 325 - 333
3)Dr. G. K. Jani, Pharmaceutics 2, 6
th edition, B. S. Shah Prakashan, Page no. 202-
205
4)S. Akbari et al. International Journal of Innovative Research and Scientific
Studies, 1 (1) 2018, Pages: 14-21
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REFERENCES

38. Prepared by: Bhargavi Mistry 38
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