The document discusses pharmaceutical emulsions, defining them as mixtures of immiscible liquids where one liquid is dispersed as droplets throughout another. It outlines types of emulsions, their stability, identification methods, formulation components, and various emulsifying agents while detailing their mechanisms of action. Additionally, it covers preparation methods and the Hydrophile-Lipophile Balance (HLB) system to select appropriate emulsifying agents based on desired product characteristics.

1. Pharmaceutical Emulsions
Version 2.0
(Dr.) Mirza Salman Baig
Assistant Professor (Pharmaceutics)
AIKTC, School of Pharmacy,New Panvel
Affiliated to University of Mumbai (INDIA)

2. 2
An Emulsion is a mixture of two or more
Immiscible liquids.
•Emulsion, is a mixture of two or more liquids
in which one is present as droplets distributed
throughout the other.
OilOil
WaterWater
Oil
Water
Agitation
Separate rapidly into two
clear defined layers
OilOil
WaterWater
Oil
Water
Agitation
Separate rapidly into two
clear defined layers

4. Internal Phase or External Phase in
Emulsions:
➢The dispersed liquid is known as the Internal or
Discontinuous phase.
➢ Whereas the dispersion medium is known as
the External or Continuous phase

5. Types Of Emulsions
Based on dispersed phase:
➢ Oil in Water (O/W): Oil droplets dispersed in
water.
➢ Water in Oil (W/O): Water droplets dispersed in
oil.
➢ Water in Oil in water (W/O/W): Water in Oil
emulsion dispersed in water – multiple emulsion.
Based on size of liquid droplets:
➢ 0.2 – 50 mm Macroemulsions
➢ 0.01 – 0.2 mm Microemulsions

6. Instabilities in Emulsion:
➢Emulsions are, by nature, physically unstable; that is, they
tend to separate into two distinct phases or layers over
time.
➢ Creaming occurs when dispersed oil droplets merge and
rise to the top of an o/w emulsion or settle to the bottom in
w/o emulsions. In both cases, the emulsion can be easily
redispersed by shaking.
➢Coalescence (breaking or cracking) is the complete
and irreversible separation and fusion of the dispersed
phase.
➢Phase inversion or a change from w/o to o/w (or vice
versa) may occur. This is considered a type of instability by
some.

7. Identification test for Emulsions:
By using Naked eye, it is very difficult to
differentiate between o/w or w/o
emulsions. Thus, the following methods
have been used to identify the type of
emulsions.
1) Dye Test
2) Dilution Test
3) Electrical conductivity Test
4) Fluorescence Test.
5) Cobalt Chloride Test.

8. Formulation of Emulsion
• Drug (medicament)
• Oil Phase
• Aqueous phase
• Emulsifying agent (emulsifier)
• Antioxidants
• Preservatives
• Organoleptic additives
– Flavouring agents
– Colouring agent

9. Emulsifying Agent:
➢Emulsions are stabilized by adding an emulsifying
agent.
➢These agents have both a hydrophilic and
Lipophilic part in their chemical structure.
➢All emulsifying agents get adsorbed at the Oil :
Water interface to provide a protective barrier
around the dispersed droplets.
➢In addition to this protective barrier, emulsifiers
stabilize the emulsion by reducing the interfacial
tension of the system.

10. Water
Oil

11. Classification Of Emulsifying Agents:
Emulsifying agents can be classified according to
1) Chemical nature:
➢Synthetic Emulsifying Agents
➢Natural Emulsifying Agents
➢Finely Dispersed Solids
➢Other emulsifying Agents
2) Mechanism of action:
✓Monomolecular
✓Multi-molecular
✓Solid particle films.

12. Synthetic Emulsifying Agents
1) (pH > 8))
✓ Sodium or potassium oleate
✓ Triethanolamine stearate
✓ sodium lauryl sulfate.
2) Cationic: (pH 3-7)
✓ Benzalkonium chloride,
✓ Benzethonium chloride
✓ Quaternary ammonium salts.
3) Non Ionic (pH 3-10)
✓ Polyglycol,
✓ Fatty acid esters,
✓ Lecithin.
✓ Sorbitan esters (Spans).
✓ Polyoxyethylene derivatives of sorbitan esters (Tweens),
✓ Glyceryl esters.
Cationic and Anionic surfactants are generally limited to use in topical, o/w emulsion

13. Natural Emulsifying Agents
Derived from Plants and Animals:
Vegetable derivatives:
• Acacia
• Tragacanth
• Agar
• Pectin
• Carrageenan
• Lecithin (egg)
Animal derivatives:
• Gelatin
• Lanolin
• Cholesterol

14. Finely Divided or Finely Dispersed
Solid Particle Emulsifiers
These agents form a particulate layer around
dispersed particles. Most will swell in the
dispersion medium to increase viscosity and
reduce the interaction between dispersed droplets.
Most commonly they support the formation of o/w
emulsions,
E.g.
• Bentonite
• Veegum,
• Hectorite,
• Magnesium Hydroxide,
• Aluminum Hydroxide

15. Other Emulsifying Agents
A variety of fatty acids (e.g., stearic acid),
fatty alcohols (e.g., stearyl or cetyl alcohol), and
fatty esters (e.g., glyceryl monostearate) serve to
stabilize emulsions through their ability as
thickening agent the emulsion..

16. Droplet Stabilization
1) Interfacial tension theory
2) Interfacial film
3) Electric repulsion

17. 1) Interfacial tension
• Lowering interfacial tension is important
way to decrease the free surface energy
associated with the formation of droplets.
• Thermodynamic stabilization

18. 2) Interfacial film
• Surface active agents tends to concentrate
at interface
• Emulsifier adsorb at oil-water interface to
form monomolecular layer which prevents
coalescence of internal phase

19. 3) Electric repulsion
• If the emulsifier is ionized, the presence of
strong charge may lead to repulsion in
droplets and hence increasing stability.

20. 3) Electric repulsion
• The oil globules in a pure oil and pure water
emulsion carry a negative charge.
• The water ionizes so that both hydrogen and
hydroxyl ions are present.
• The negative charge on the oil may come
from adsorption of the OH ions. These
adsorbed hydroxyl ions form a layer around the
oil globules.
• A second layer of oppositely charged ions forms
a layer in the liquid outside the layer of negative
ions.
• The electric charge is a factor in all emulsions,
even those stabilized with emulsifying agents

21. HLB
• A system was developed to assist in making
systemic decisions about the amounts and types
of surfactants needed in stable products.
• The system is called the HLB (hydrophile-
lipophile balance) system and has an arbitrary
scale of 1 - 18.
• HLB numbers are experimentally determined for
the different emulsifiers. .

22. ✓Low number of hydrophilic groups on the Molecule
thus imparting Lipophilic character:
✓ Spans have low HLB numbers, Because of their
oil soluble character, Spans will cause the oil phase
to predominate and form an w/o emulsion.
High HLB indicates ?
Emulsifier has many hydrophilic groups on the
molecule thus imparting hydrophilic Character.
Tweens have higher HLB numbers, because of their
water-soluble character, Tweens will cause the
water phase to predominate and form an o/w
emulsion.
HLB

23. HLB range Role
1-3 Anti-foaming agent
3-6 W/O emulsifying agents
7-9 Wetting agents
8-13 O/W emulsifying agents
13-15 Detergents
15-18 Solubilizing Agents
HLB

24. Selection of emulsifying Agent
• Types of Emulsifying agents
– Surfactant
– Hydrophilic colloids
– Finely divided solids
• Selection basis
– Shelf life (Stability)
– Type of emulsion
– Cost

25. • Definition: The hydrophile-lipophile balance
(HLB) system is an arbitrary scale for
expressing the hydrophilic and lipophilic
characteristics of an emulsifying agent.
• Agents with HLB value of 1-8 are lipophilic and
suitable for preparation of w/o emulsion, and
those with HLB value of 8- 18 are hydrophilic
and good for o/w emulsion.
25
HLB System

26. HLB System
The oil phase of an o/w emulsion requires a specific HLB, called
the required hydrophile–lipophile balance (RHLB).
26

27. HLB method (Griffin)
• Griffin defined HLB
• HLB= mol% Hydrophilic group/5
• Range 0-20
• Therefore, completely hydrophilic
molecule without non-polar group has HLB
value 20
• It is applicable to polyoxyethylene ether
derivatives

28. • HLBmix = f × HLBA + (1-f) × HLB B
• Where,
f is fraction of surfactant A in surfactant mixture
HLB method (Griffin)
Required HLB

29. HLB method (Davis)
• Davies suggested a method based on
calculating a value based on the chemical
groups of the molecules

30. HLB System
30
Calculations
Example
Calculate the amounts (ml) of each of the emulsifiers (tween
80 and span 80) that are required to prepare the emulsion:
Ingredient Amount RHLB (O/W)
1. Beeswax 15 g 9
2. Lanolin 10 g 12
3. Paraffin wax 20 g 10
4. Cetyl alcohol 5 g 15
5. Emulsifiers (Tween 80 + Span 80) 5 ml
6. Preservative As required
7. Color 0.2 g
8. Water, purified q.s. 100 ml

31. HLB System
Calculations
Example
First, calculate the overall RHLB of the emulsion by
multiplying the RHLB of each oil-like component (items 1-
4) by their weight fraction from the oil phase. The total
weight of the oil phase is 50 g. Therefore:
Beeswax 15/50 × 9 = 2.70
Lanolin 10/50 × 12 = 2.40
Paraffin 20/50 × 10 = 4.00
Cetyl alcohol 5/50 × 15 = 1.50
Total RHLB for the emulsion =10.60

32. HLB System
Calculations
Example
Next, a blend of two emulsifying agents is chosen, one with an HLB
above the RHLB of the emulsion (Tween 80, HLB = 15) and the
other with an HLB below the RHLB (Span 80, HLB
= 4.3)
Calculate the percentages of the emulsifiers using the formula:
% Surfactant with High HLB=
RHLB- HLB Low
HLB High- RHLB
% Tween =
10.6 − 4.3
15 − 4.3
= 0.59
Therefore, 5 ml × 0.59 = 2.95 ml of Tween 80
and the remainder, 2.05 ml, must be supplied by Span 80

33. Phase Inversion Temperature
• o/w emulsion stabilized by non-ionic emulgent,
on heating undergoes inversion to w/o
• Reason: at high temperature emulgent become
more hydrophobic
• The temperature at which emulgent has equal
hydrophilicity and hydrophobicity, phase
inversion takes place
• PIT could also be related to stability of emulsion

34. Micellisation
• Micelles are formed when the
concentration of a surfactant
reaches a given concentration
called critical micelle
concentration (CMC) in
which the surface is saturated
with surfactant molecules.
• The main reason for micelle
formation is to obtain a
minimum free energy state.
• In a micelle, polar or ionic
heads form an outer shell in
contact with water, while non-
polar tails are sequestered in
the interior to avoid water.
Concentration
SurfaceTension

35. Cloud point
• For non-ionic surfactants, Increasing temperature
increases micellar size and decrease CMC.
• The effect of temperature stops at a characteristic
temperature called the cloud point where the
solution become turbid due to the separation of the
solution into two phases.
Temperature has a comparatively small effect on the
micellar properties of ionic surfactants.

36. Methods of Preparation Of
Emulsions:
Commercially, emulsions are prepared in large
volume mixing tanks and refined and stabilized by
passage through a colloid mill or homogenizer.
Extemporaneous production is more concerned
with small scale methods.
• Dry Gum Methods
• Wet Gum Methods
• Bottle Method
• Beaker Method.
• In situ Soap Method.

37. DRY GUM Method for Preparation of
Emulsions:
Dry gum method is used to prepare the initial
or primary emulsion by mixing Oil and Gum
then slowly adding water

38. Procedure:
• Take mortar, 1 part gum is levigated with the 4
parts oil until the powder is thoroughly wetted;
then the 2 parts water are added all at once,
and the mixture is vigorously triturated until the
primary emulsion formed is creamy white and
produces a "cliking" sound as it is triturated.
• Active ingredients, preservatives, color, flavors
are added as a solution to the primary
emulsion.
• When all agents have been incorporated, the
emulsion should be transferred to a calibrated
vessel, brought to final volume with water.

40. Wet Gum Method
Fixed Oil : Water : Emulsifier (gum) … 4:2:1
Mineral Oil : Water : Emulsifier (gum) … 3:2:1
Volatile Oil : Water : Emulsifier (gum) … 2:2:1
Procedure:
• In this method, the proportions of (fixed) oil, water, and
emulsifier are the same (4:2:1), but the order and
techniques of mixing are different.
• The 1 part gum is triturated with 2 parts water to form a
mucilage; then the 4 parts oil is added slowly, in portions,
while triturating.
• After all the oil is added, the mixture is triturated for
several minutes to form the primary emulsion.
• Then other ingredients may be added as in the
continental method.

41. Bottle Method
➢This method may be used to prepare emulsions of
volatile oils, Oleaginous substances of very low
viscosities.
➢This method is a variation of the dry gum method.
➢One part powdered acacia (or other gum) is
placed in a dry bottle and four parts oil are added.
➢ The bottle is capped and thoroughly shaken.
➢To this, the required volume of water is added all
at once, and the mixture is shaken thoroughly until
the primary emulsion forms.

42. Beaker Method
➢Dividing components into water soluble and oil soluble
components.
➢ All oil soluble components are dissolved in the oily phase
in one beaker and all water soluble components are
dissolved in the water in a separate beaker.
➢Oleaginous components are melted and both phases are
heated to approximately 70°C over a water bath.
➢The internal phase is then added to the external phase
with stirring until the product reaches room temperature.

43. Liquid Paraffin Emulsion
Ingredients Qty Category
Liqiuid Paraffin 50ml Luxative
Gaum Acacia 12.5gm Emulgent
Gum Tracaganth 0.5gm Emulgent
Sodium Benzoate 0.5gm Preservative
Vanillin 0.05gm Flavour
Glycerin 12.5gm Humectant/Viscocity builder
Chloroform 0.25ml Preservative
Purified Water 100ml (q.s.) Vehicle

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