PHARMACEUTICAL EMULSION, CLASSIFICATION, APPLICATION, METHODS OF PREPARATION AND IDENTIFICATION TESTS.

PHARMACEUTICAL
EMULSION
Chinmay Sahoo
M pharm (Pharmaceutics)
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CONTENT
• Introduction
• Classification
• Application
• Formulation
• Preparation
• Identification Test
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Introduction
• An emulsion is a mixture of two or more liquids that
are normally immiscible (unmixable), where one
liquid is dispersed in the other as tiny droplets.
• Emulsion has two primary components:
⚬ Dispersed phase: The liquid that is broken into
small droplets.
⚬ Continuous phase: The liquid in which the
droplets are suspended.
• To keep the mixture from separating over time, an
additional substance called an emulsifier or
emulsifying agent is often added.
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CLASSIFICATION
EMULSION
DISPERSE
PHASE
Simple
Emulsion
Multi-
Emulsion
PARTICLE
SIZE
Macro
Emulsion
Micro
Emulsion
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Simple Emulsion
• Simple emulsions are classified into two types based on
their phases:
a. Oil-in-Water (O/W), where oil droplets are dispersed
in water
b. Water-in-Oil (W/O), where water droplets are dispersed
in oil
• The type of emulsion is determined by which liquid is
the continuous phase (the outer liquid) and which is
the dispersed phase (the inner, microscopic droplets).
CLASSIFICATION
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Simple Emulsion
Oil-in-Water (O/W)
• An O/W (oil-in-water) emulsion is a mixture where small droplets
of oil are dispersed in a continuous water phase, with water
forming the outer layer.
• O/W emulsions are often more stable than W/O emulsions in
terms of stability. This is because the dispersed oil droplets have a
more stable habitat in the continuous aqueous phase.
• O/W (oil-in-water) emulsions are stabilized by hydrophilic
surfactants or solid particles with contact angles less than 90°.
• Example: Creams, ointments, baby balms and cold cream.
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Simple Emulsion
Water-in-Oil (W/O)
• A water-in-oil (W/O) emulsion is a system where small droplets of
water are dispersed within a continuous oil phase, with the oil being
the external or continuous medium.
• W/O emulsions typically have a longer shelf life than O/W emulsions.
This is because the distributed water droplets have a more stable
environment in the continuous oil phase.
• W/O (water-in-oil) emulsions are stabilized by hydrophobic
surfactants or solid particles with a contact angle greater than 90°.
• Examples: Moisturizinglotions, some topical steroid products and
homogenized milk.
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Multi-Emulsion
• A multiple emulsion is a complex, "emulsion within an emulsion"
system where droplets of one emulsion type (e.g., water-in-oil) are
dispersed with another (e.g., oil-in-water) system.
• It leading to two types of emulsion system
a. W/O/W (water-in-oil-in-water)
b. O/W/O (oil-in-water-in-oil)
• These systems, stabilized by both hydrophilic and lipophilic
surfactants.
• These are thermodynamically unstable but are promising for
applications like controlled drug delivery and cosmetic formulations
due to their ability to provide prolonged release of active
ingredients.
CLASSIFICATION
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Multi-Emulsion
W/O/W (water-in-oil-in-water)
• A water-in-oil-in-water (W/O/W) emulsion is a complex emulsion where
water droplets are first dispersed within an oil phase (forming a W/O
emulsion), and this entire structure is then dispersed within a
continuous external water phase (forming an O/W emulsion).
• This "emulsion within an emulsion" allows for the encapsulation of
substances within the innermost water phase, protected by an oil barrier
and then a water coating.
• Example: W/O/W emulsion could be used to encapsulate a protein
within the innermost water phase, which is then surrounded by oil
droplets and dispersed in a water-based liquid, like a beverage.
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W/O/W Emulsion

Multi-Emulsion
O/W/O (oil-in-water-in-oil)
• An oil-in-water-in-oil emulsion (O/W/O) is a type of double emulsion
where water droplets are dispersed within oil droplets, and these oil
droplets are then dispersed within a continuous outer oil phase.
• These complex structures are used in food and pharmaceutical
applications, such as for encapsulated nutrients or drugs that need to be
released under specific conditions.
• Example: The encapsulation of an oil-soluble substance within oil, which
is then enclosed by a water layer, and finally dispersed into a larger oil
phase. This creates a complex structure where the water is protected and
contained within the oil layers.
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O/W/O Emulsion

Macro Emulsion
• A macroemulsion is a coarse, unstable dispersion of
immiscible liquids, like oil and water, with droplet sizes
ranging from 1 to 100 micrometers (µm).
• These systems are thermodynamically unstable, meaning
they separate over time through processes like creaming or
coalescence and are held together kinetically by emulsifiers.
• Example: Milk, which is a macroemulsion of fat droplets in
water that appears milky due to light scattering by the large
droplets.
CLASSIFICATION
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Micro Emulsion
• A micro emulsion is a thermodynamically stable, transparent,
and isotropic liquid mixture of two immiscible liquids (like oil
and water) stabilized by a high concentration of surfactants
(emulsifiers) and often a co-surfactant.
• These systems form very small droplets (typically 1–100 nm),
creating a single, clear phase that is distinct from a cloudy
conventional emulsion.
• Example: A transparent drug delivery system, where oil and
water-soluble drugs can be simultaneously encapsulated and
delivered to the body in a stable, clear solution.
CLASSIFICATION
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Drug Delivery Systems
APPLICATION
Emulsions enhance solubility and
bioavailability of poorly water-
soluble drugs.
Parenteral Nutrition
Intravenous emulsions deliver
essential fatty acids and calories to
patients unable to eat.
Topical Formulations
Commonly used in creams,
lotions, and ointments for skin
application.
Oral Formulations
Improve taste masking and
palatability of bitter drugs.
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Vaccine Delivery
Emulsions act as adjuvants to
enhance immune response (e.g.,
MF59 in influenza vaccines).
Used in eye drops to improve drug
retention and comfort (e.g.,
cyclosporine emulsion for dry eye).
Ophthalmic Preparations

• Improved Bioavailability: Emulsions can increase the rate of dissolution and
absorption, thus improving the bioavailability of poorly soluble drugs.
• Taste Masking: The oily phase can dissolve and encapsulate drugs with
unpleasant tastes, making them more palatable for oral administration.
• Protection of Active Ingredients: Emulsification can protect active ingredients
from degradation, helping to preserve their activity.
• Enhanced Aesthetics: They provide a desirable texture and appearance to
topical formulations.
• Delivery of Incompatible Ingredients: Emulsions can keep two incompatible
ingredients separate within their respective phases, allowing for the
formulation of otherwise unstable products.
BENEFITS
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CHALLENGES
Stability Challenges
• Coalescence: Droplets of the dispersed phase merge into
larger droplets, leading to separation.
• Creaming/Sedimentation: Droplets separate due to density
differences and rise to the top (creaming) or settle to the
bottom (sedimentation).
• Flocculation: Droplets clump together without merging,
forming larger aggregates but retaining their individual form.
• Phase Inversion: The types of phases switch, for example,
from oil-in-water to water-in-oil, or vice-versa.
• Ostwald Ripening: Smaller droplets shrink and larger droplets
grow over time, leading to instability.
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Microbial and Chemical Challenges
• Microbial Contamination: Emulsions are
susceptible to microbial growth, which
can deteriorate the product and cause
physical separation. Preservatives are
needed to prevent this.
• Contamination with Emulsifiers: In
some processes, polymer products can be
contaminated with traces of emulsifiers,
affecting transparency and other
properties.

CHALLENGES
Production and Quality Challenges
• Inadequate Shear and Emulsifier Distribution: Insufficient
shear energy or poor distribution of emulsifiers can result in
large, unstable oil droplets.
• Air Inclusions: Unwanted air bubbles can create uneven
texture, reduced volume, and a poor appearance.
• Particulate Settling: Flavoring particles, herbs, or other
solids can settle unevenly in the emulsion, leading to a
layered appearance and inconsistent flavor.
• Temperature and Environmental Sensitivity: Emulsions can
be sensitive to temperature and other environmental factors,
affecting their stability and appearance.
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Scaling and Regulatory Challenges
• Lab to Production Scale-Up:
Transferring a successful lab-scale
emulsion to large-scale production can
be difficult due to different mixing
conditions and processes, impacting
product quality.
• Environmental and Regulatory Issues:
Meeting regulatory standards for
microbial load and other factors is a
significant challenge.

Selection of Emulsifying agents (emulsifiers):
• An emulsifying agent is any material that enhances the stability of an
emulsion.
• The ideal emulsifying agent is colorless, odorless, tasteless, nontoxic, non-
irritant and able to produce stable emulsions at low concentrations.
• Examples of Emulsifying agent:
⚬ Carbohydrate Materials: Ex.: Acacia, Tragacanth, Agar, Pectin, o/w
emulsion.
⚬ Protein Substances: Ex.: Gelatin, Egg yolk, Casein o/w emulsion.
⚬ High Molecular Weight Alcohols: Ex.: Stearyl Alcohol, Cetyl Alcohol,
Glyceryl Mono stearate o/w emulsion, cholesterol w/o emulsion.
⚬ Wetting agents: Anionic, Cationic, Nonionic (o/w emulsion w/o emulsion).
⚬ Finely divided solids: Bentonite, Magnesium Hydroxide, Aluminum
Hydroxide o/w emulsion.
FORMULATION
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Tragacanth

TYPES CLASS EXAMPLE
EMULSION
TYPE
ROUTE OF
ADMINISTRATION
Anionic
Alkyl sulfates Sodium lauryl sulfate Oil in water Topical
Monovalent salts of fatty acids Sodium stearate Oil in water Topical
Divalent salts of fatty acid Calcium oleate Water in oil Topical
Cationic Quaternary ammonium compounds Cetrimide Oil in water Topical
Nonionic
Alcohol polyethylene glycol ethers Cetomacrogol 1000 Oil in water Topical
Fatty acid polyethylene glycol esters Polyethylene glycol 40 stearate Oil in water Topical
Sorbitan fatty acid esters Sorbitan monooleate (Span 80) Water in oil Topical
Polyoxyethylene sorbitan fatty acid esters
Polyoxyethylene sorbitan monooleate
(Tween 80)
Oil in water Topical, parenteral
Fatty
Amphiphiles
Fatty alcohols Cetyl alcohol Water in oil Topical
Fatty acids Stearic acid Water in oil Topical
Monoglycerides Glyceryl monostearate Water in oil Topical
Polymeric Polyoxyethylene–polyoxypropylene block copolymers Poloxomers (Pluronic F-68) Oil in water Parenteral
SURFACE ACTIVE EMULSIFYING AGENTS

An ideal emulsifying agent should posses the following characteristics:
• It should be able to reduce the interfacial tension between the two immiscible liquids.
• It should be physically and chemically stable, inert and compatible with the other ingredients of the
formulation.
• It should be non irritant and non toxic in the continuous used.
• It should be organoleptically inert i.e. should not impart any colour , oduor or taste to the
preparation.
• It should be able to produce and maintain the required viscosity of the preparation.
• It should be able to form a coherent film around the globules of the dispersed phase and should
prevent the coalescence of the droplet the dispersed phase.
Criteria For The Selection of
Emulsifying Agents
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PREPARATION OF EMULSION
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• Emulsion preparation involves creating a
stable mixture of two immiscible liquids,
oil and water, using an emulsifier and
mechanical force.
• The methods commonly used to prepare
emulsions can be divided into following
categories
a.Trituration Method
1. Dry Gum Method
2. Wet Gum Method
b.Bottle Method
c. Auxiliary method

Trituration Method
Dry Gum Method
• In this method the oil is first triturated with gum with a little
amount of water to form the primary emulsion.
• The trituration is continued till a characteristic 'clicking' sound is
heard and a thick white cream is formed.
• Once the primary emulsion is formed, the remaining quantity of
water is slowly added to form the final emulsion.
• This method consists of
⚬ "4:2:1" formula
⚬ 4 parts (volumes) of oil
⚬ 2 parts of water
⚬ 1 part of gum
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Trituration Method
Wet Gum Method
• As the name implies, in this method first gum and water are triturated
together to form a mucilage.
• The required quantity of oil is then added gradually in small
proportions with thorough trituration to form the primary emulsion.
• Once the primary emulsion has been formed remaining quantity of
water is added to make the final emulsion.
• This method consists of
⚬ "4:2:1" formula
⚬ 4 parts (volumes) of oil
⚬ 2 parts of water
⚬ 1 part of gum
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Bottle Method
• This method is employed for preparing emulsions containing volatile
and other non-viscous oils.
• Both dry gum and wet gum methods can be employed for the
preparation.
• As volatile oils have a low viscosity as compared to fixed oils, they require
comparatively large quantity of gum for emulsification.
• In this method, oil or water is first shaken thoroughly and vigorously
with the calculated amount of gum.
• Once this has emulsified completely, the second liquid (either oil or
water) is then added all at once and the bottle is again shaken vigorously
to form the primary emulsion.
• More of water is added in small portions with constant agitation after
each addition to produce the final volume.
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Auxiliary method
• An auxiliary method of emulsion involves a secondary process, such as
using a homogenizer, to improve the quality of a primary emulsion
prepared by a standard method like the wet or dry gum method.
• The primary goal of an auxiliary method is to enhance the emulsion by
reducing dispersed droplet size, which increases stability and quality.
• Example:
⚬ A common auxiliary method involves passing the emulsion through
a hand homogenizer.
⚬ This device uses a pumping action to force the emulsion through
very small openings, thereby reducing the dispersed droplet size to
typically 5 microns or less.
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IDENTIFICATION TESTS FOR AN
EMULSION
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Identification tests for an emulsion determine if it is oil-in-water (o/w) or water-in-oil (w/o)
and include the Dilution Test (stable with water for o/w, stable with oil for w/o), the Conductivity
Test (o/w conducts electricity, w/o does not), and the Dye Test (water-soluble dyes color the
continuous phase of o/w, oil-soluble dyes color w/o).
Dilution Test:
• Procedure: Add a small amount of the emulsion to
either water or oil.
• Result:
⚬ If the emulsion is an o/w emulsion, it will remain
stable when water is added but will break
(demulsify) when oil is added.
⚬ If the emulsion is a w/o emulsion, it will remain
stable when oil is added but will break when water
is added.

EMULSION
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Dye Test (Solubility Test):
• Procedure: Add a water-soluble or oil-soluble dye to the
emulsion and observe it under a microscope.
• Result:
⚬ In an o/w emulsion, a water-soluble dye will color the
continuous phase (water) uniformly, while an oil-soluble
dye will form colored droplets.
⚬ In a w/o emulsion, an oil-soluble dye will color the
continuous phase (oil) uniformly, while a water-soluble dye
will form colored droplets.
Filter Paper Test:
• Procedure: Place a drop of the emulsion on a piece of filter
paper.
• Result:
⚬ An o/w emulsion will spread rapidly, forming a watery
stain.
⚬ A w/o emulsion will migrate slowly, leaving behind oily
spots.

EMULSION
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Conductivity Test:
• Procedure: Place two electrodes connected to a light bulb
circuit into the emulsion.
• Result:
⚬ An o/w emulsion will transmit electricity, causing the light
bulb to glow because water conducts electricity.
⚬ A w/o emulsion will not transmit electricity, and the light
bulb will not glow.
Cobalt Chloride Paper Test:
• Procedure: Place a drop of the emulsion on cobalt chloride
paper, which turns from blue to pink in the presence of water.
• Result:
⚬ If the paper turns pink, it indicates the presence of water as
the continuous phase, meaning it is an o/w emulsion.
⚬ If the paper remains blue, it suggests oil is the continuous
phase, indicating a w/o emulsion.

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PHARMACEUTICAL EMULSION, CLASSIFICATION, APPLICATION, METHODS OF PREPARATION AND IDENTIFICATION TESTS.

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