Outcomes of this lecture
1- Definition and Classification of Emulsion
2- Pharmaceutical and medical application of
Emulsion
3- Theories of Emulsification
4- Formulation of Emulsion
5- Emulsifying agants
6- Stability of suspensions & Quality control
An emulsion is liquid preparation
containing two immiscible liquids, one of
which is dispersed as globules
(dispersed phase = internal phase)
in the other liquid
(continuous phase = external phase).
Continuous phase
D ispersed phase
To stabilize these droplets, emulsifying agent should be added
Microemulsion: Droplets size range 0.01 to 0.1 m m
Macroemulsion: Droplets size range approximately 5 m m.
General Types of Pharmaceutical
Emulsions:
1) Lotions
2) Liniments
3) Creams
4) Ointments
5) Vitamin drops
Types of Emulsion
mm
Water
Oil
Oil-in-water emulsion
Water-in-oil emulsion
Primary and secondary emulsion:

Primary emulsion containing one internal
phase, for example, oil-in-water emulsion
(o/w) and water-in-oil emulsion (w/o).

Secondary emulsion= multiple-emulsion: it
contains two internal phase, for instance,
o/w/o or w/o/w. It can be used to delay
release or to increase the stability of the
active compounds.
Multiple Emulsions
mm
Water
Oil
Water-in-oil-in-water emulsion
Oil-in-water-in-oil emulsion
O il
W ater
W ater
O il
W /O
O /W
W ater
O il
O il
W ater
O il
O /W /O
W ater
W /O /W
Emulsion Size

A



< 0.5 mm
0.5-1.5 mm
1.5-3 mm
>3 mm
Number Distributions
•
•
•
•
< 0.5 mm
0.5-1.5 mm
1.5-3 mm
>3 mm
Very few large
droplets contain
most of the oil
Chemical Composition
Interfacial layer. Essential to
stabilizing the emulsion
Oil Phase. Limited effects on
the properties of the emulsion
Aqueous Phase. Aqueous
chemical reactions affect the
interface and hence emulsion
stability
Emulsion Type and Means of Detection:
using of naked eye, it is very difficult to
differentiate between o/w or w/o
emulsions.
Thus, the four following methods have
been used to identify the type if
emulsions.
1) Dilution Test:
based on the solubility of external phase of
emulsion.
- o/w emulsion can be diluted with water.
- w/o emulsion can be diluted with oil.
F ew drops
of w ater
F ew drops
of em ulsion
W ater distribute
uniform ly
O /W em ulsion
W ater separate
out as layer
W /O em ulsion
2) Conductivity Test:
water is good conductor of electricity whereas
oil is non-conductor. Therefore, continuous
phase of water runs electricity more than
continuous phase of oil.
B u lb
E lectro d e
E m u lsio n
= Bulb glows with O/W
= Bulb doesn’t glow with W/O
3) Dye-Solubility Test:
-
Water-soluble dye will dissolve in the
aqueous phase.
-
Oil-soluble dye will dissolve in the oil phase.
O il-soluble dye (e.g. S carlet)
W /O
O /W
W ater-soluble dye (e.g. A m aranth dye)
O /W
W /O
What is look like under the microscope after mixing with suitable dye
4-Fluorescence test:

oils give fluorescence under UV light, while
water doesn’t. Therefore, O/W emulsion
shows spotty pattern while W/O emulsion
fluoresces.
Pharmaceutical applications of emulsions:
1 ) To mask the taste
2) O/W is convenient means of orally administration of
water-insoluble liquids
3) O/W emulsion facilitates the absorption of waterinsoluble compounds comparing to their oily solution
preparations (e.g. vitamins)
4) Oil-soluble drugs can be given parentrally in form of
oil-in water emulsion. (e.g Taxol)
5) Emulsion can be used for external application in
cosmetic and therapeutic uses.
Theories of Emulsification:

Incase of two immiscible liquids
O il
O il
W ater
A gitation
O il
W ater
W ater
Separate rapidly into tw o
clear defined layers

An explanation of this phenomenon is because
of cohesive force between the molecules of each
separate liquid exceeds adhesive force between
two liquids. This is manifested as interfacial
energy or tension at boundary between the
liquids.
Sm all droplet
 Surface area
Therefore, to prevent the
coalescence and separation,
emulsifying agents have been used.
 Interfacial tension
System is therm odynam ically
unstable “ high energy”
System tends to separate in
tw o layer to reduce the surface area
Types of emulsifying agents:
1) Surface active agent: adsorbed at oil/water
interface to form monomolecular film to reduce
the interfacial tension
2) Hydrophilic colloids: forming a multimolecular
film around the dispersed droplet
3) Finely divided solid particles: they are adsorbed
at the interface between two immiscible liquid
phases to form particulate film
A- Monomolecular adsorption
W =   .
A
Surface area
Surface free
energy
Interfacial tension
In emulsion, the surface area is high to maintain
the dispersion of the droplets. Thus, based on
the above equation surface free energy
becomes high consequently. The only way to
keep it low is to reduce the interfacial tension.
Surface active agent (SAA) is molecule which
have two parts, one is hydrophilic and the
other is hydrophobic. Upon the addition of
SAA, they tend to form monolayer film at the
oil/water interface.
H ydrophilic
head
H ydrophobic
tail
W a te r
O il
Form
monomolecular
film
The functions of surface active agents to provide
stability to dispersed droplets are as following:
1) Reduction of the interfacial tension
2) Form coherent monolayer to prevent the coalescence of
two droplet when they approach each other
3) Provide surface charge which cause repulsion between
adjust particles

Combination of surface-active agents is used most frequently. The
combination should form film that closely packed and condensed
Classification of Emulsifying surfactants
1) Anionic group
2) Cationic group
3) Amphoteric group
4) Nonionic group
Classification of Emulsifying surfactants
Classification of surfactants



The "tail" of most surfactants are fairly similar,
consisting of a hydrocarbon chain, which can be
branch, linear, or aromatic.
Fluorosurfactants have fluorocarbon chains.
Siloxane surfactants have siloxane chains.
Classification of surfactants




Most commonly, surfactants are classified according
to polar head group.
A non-ionic surfactant has no charge groups in its
head.
The head of an ionic surfactant carries a net charge.
If the charge is negative, the surfactant is more
specifically called anionic; if the charge is positive,
it is called cationic.
If a surfactant contains a head with two oppositely
charged groups, it is termed zwitterionic.
Anionic


Sulfate, sulfonate, phosphate, and carboxylates.
ammonium lauryl sulfate, sodium lauryl sulfate
(SDS, sodium dodecyl sulfate, another name for the
compound) and the related alkyl-ether sulfates
sodium laureth sulfate, also known as sodium lauryl
ether sulfate (SLES), and sodium myreth sulfate.
Docusates: dioctyl sodium sulfosuccinate,
perfluorooctanesulfonate (PFOS),
perfluorobutanesulfonate, linear alkylbenzene
sulfonates (LABs).
Anionic
Carboxylates
These are the most common surfactants and
comprise the alkyl carboxylates (soaps), such
as sodium stearate. More specialized species
include sodium lauroyl sarcosinate and
carboxylate-based fluorosurfactants such as
perfluorononanoate, perfluorooctanoate
(PFOA or PFO).

Cationic head groups

pH-dependent primary, secondary, or tertiary
amines:
Primary amines become positively charged at
pH < 10, secondary amines become charged
at pH < 4:

Octenidine dihydrochloride;
Cationic head groups

Permanently charged quaternary ammonium cation:
 Alkyltrimethylammonium salts: cetyl trimethylammonium
bromide (CTAB) a.k.a. hexadecyl trimethyl ammonium bromide,
cetyl trimethylammonium chloride (CTAC
 Cetylpyridinium chloride (CPC)
 Benzalkonium chloride (BAC)
 Benzethonium chloride (BZT)
 5-Bromo-5-nitro-1,3-dioxane
 Dimethyldioctadecylammonium chloride
 Cetrimonium bromide
 Dioctadecyldimethylammonium bromide (DODAB)
Zwitterionic surfactants
(amphoteric)



The cationic part is based on primary, secondary, or
tertiary amines or quaternary ammonium cations.
The anionic part can be more variable and include
sulfonates, as in CHAPS (3-[(3Cholamidopropyl)dimethylammonio]-1propanesulfonate).
Other anionic groups are sultaines illustrated by
cocamidopropyl hydroxysultaine. Betaines, e.g.,
cocamidopropyl betaine. Phosphates: lecithin
Nonionic surfactant


Many long chain alcohols exhibit some surfactant
properties.
Prominent among these are the fatty alcohols cetyl
alcohol, stearyl alcohol, and cetostearyl alcohol
(consisting predominantly of cetyl and stearyl
alcohols), and oleyl alcohol.
Nonionic surfactant
Polyoxyethylene glycol alkyl ethers (Brij):
CH3–(CH2)10–16–(O-C2H4)1–25–OH:
- Octaethylene glycol monododecyl ether
- Pentaethylene glycol monododecyl ether

Polyoxypropylene glycol alkyl ethers:
CH3–(CH2)10–16–(O-C3H6)1–25–O

Nonionic surfactant

Glucoside alkyl ethers:
CH3–(CH2)10–16–(O-Glucoside)1–3–OH:
- Decyl glucoside,
- Lauryl glucoside
- Octyl glucoside
Nonionic surfactant
Polyoxyethylene glycol octylphenol ethers:
C8H17–(C6H4)–(O-C2H4)1–25–OH: Triton X-100

Polyoxyethylene glycol alkylphenol ethers:
C9H19–(C6H4)–(O-C2H4)1–25–OH:
- Nonoxynol-9

Glycerol alkyl esters:
- Glyceryl laurate

Nonionic surfactant






Polyoxyethylene glycol sorbitan alkyl esters:
Polysorbate
Sorbitan alkyl esters: Spans
Cocamide MEA, cocamide DEA
Dodecyldimethylamine oxide
Block copolymers of polyethylene glycol and
polypropylene glycol: Poloxamers
Polyethoxylated tallow amine (POEA).
B- Multimolecular adsorption

Hydrophilic colloids form multimolecular
adsorption at the oil/ water interface. They have
low effect on the surface tension.

Their main function as emulsion stabilizers is by
making coherent multi-molecular film. This film
is strong and resists the coalescence.

They have, also, an auxiliary effect by increasing
the viscosity of dispersion medium.

Most of the hydrophilic colloids form oil-inwater emulsions.

Some of them can provide electrostatic
repulsion like acacia, which contains Arabic
acid and proteins (COOH and NH3)
colloids:
Polysaccharides
c o llo id s
A cacia
A m photerics
G elatin
Synthetic or sem i-synthetic
polym ers
C arbom er resins
A gar
C ellulose ethers
A lginic acid
C arboxym ethyl chitin
C arrageenan
PEG -n (ethylene oxide
G uar gum
polym er)
K arraya gum
Tragacanth
C- Solid particle adsorption

Finely divided solid particles are adsorbed at the
surface of emulsion droplet to stabilize them.

Those particles are wetted by both oil and water
(but not dissolved) and the concentration of these
particles form a particulate film that prevent the
coalescence.

Particles that are wetted preferentially by water
form o/w emulsion, whereas those wetted more
by oil form w/o emulsion

Note that they are very rare to use and can
affect rheology of the final product

Size of the particle is very important, larger
particles can lead to coalescence
Finely divided solids:
B entonite
H ectorite
F inely divided solids
K aolin
M agnesiu m alu m in u m silicate
M ontm orillonite
A lu m inu m h ydroxide
M agesiu m h ydroxide
S ilica
Other emulsifying agents

Egg yolk: it contains phospholipids and cholesterol.
The main withdraw back is that spoils quickly;
therefore, it can’t be used in industry.

Wool fat: anhydrous lanolin, it is used to prepare
w/o emulsion for external uses.

Starch: it forms starch mucilage and it is restricted
for enemas preparation.

Cholesterol: it has stabilizing action; therefore,
another emulsifier should be included.
CRITERIA FOR THE SELECTION OF
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 completely non irritant and non toxic in the
concentrations used .
It should be organoleptically inert i.e. should not impart any
colour, odour or taste to 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
droplets of the dispersed phase .
It should be able to produce and maintain the required viscosity
of the preparation.
Selection of Emulsifying Agents using
HLB method
A system was developed by William C. Griffin to assist
making systemic decisions about the amounts and types
of surfactants needed in stable products. The system is
called the HLB (hydrophile-lipophile balance) system.
HLB RANGE
3-0
6-4
9-7
18-8
15-13
18-10
USE
Antifoaming agents
W/O emulsifying agent
Wetting agents
O/W emulsifying agent
Detergents
Solubilizing agents
Emulsifier with low HLB

An emulsifier having a low HLB number
indicates that the number of hydrophilic groups
present in the molecule is less and it has a
lipophillic character .
For example, spans generally have low HLB
number and they are also oil soluble. Because of
their oil soluble character, spans cause the oil
phase to predominate and form a w/o emulsion.
Emulsifier with high HLB

A higher HLB number indicate that the
emulsifier has a large number of hydrophilic
groups on the molecule and therefore is more
hydrophilic in character .
Tweens have higher HLB numbers and they are
also water soluble. Because of their water
soluble character, tweens will cause the water
phase to predominate and form an o/w
emulsion.
DISADVANTAGE OF THE HLB SYSTEM
It does not take into account:
-the effect of temperature
-the presence of additives
-the concentration of emulsifier
HLB values of some common emulsifying agents
Emulsifying Agent
Acacia:
Polysorbate :)20 neewT(20
Polysorbate :)60 neewT( :60
Polysorbate :)80 neewT(80
Oleic acid:
Sorbitan monolaurate (Span :)20
Sorbitan monolaurate (Span :)60
Sorbitan monolaurate (Span :)80
HLB Value
8
16.7
14.9
15
4.3
8.6
4.7
4.3
How to control emulsion type during
formulation?

Volume of internal and external phases controls
the type of emulsion.
The smaller volume will be for the internal phase and the larger
volume will be for external phase. In some cases, internal phases can
be more than 50% of the total volume.

Dominance of polar and non-polar
characteristic of emulsifying agents
(relative
solubility of emulsifying agent in water and oil).
Dominance of polar part results in formation of o/w emulsion and
dominance of non-polar part results in formation of w/o emulsion.
Note that polar groups are better barriers than non-polar; therefore,
o/w emulsion can be prepared with more than 50 % of oil phase “
internal phase”.
What the factors that affect the choice
of emulsion type?
The choice of emulsion depends on:
(1)-properties and uses of final products
(2)- the other material required to be present.




Oil-soluble drug is prepared in o/w emulsion due its solubility and
its taste can be masked by adding flavoring agents
For intravenous injection “ i.v.” o/w emulsion is the only type
could be used.
For intramuscular injection “i.m.” both o/w and w/o types of
emulsion could be used. Water-soluble drug can be prepared in
w/o emulsion to get prolonged action (depot therapy)
Topical application:
 Semisolid emulsions are called creams and lotions
DIFFERENCE BETWEEN O/W AND
W/O EMULSIONS
Oil in water emulsion









Water is the dispersion medium and oil is the dispersed phase
For insoluble drug
For local effect
Easily to wash from skin
Doesn’t have greasy texture of oily preparation
Acceptable by consumer
They are used externally to provide cooling effect e.g.
vanishing cream
Water soluble drugs are more quickly released from o/w
emulsions
They are preferred for formulations meant for internal use as
bitter taste of oils can be masked.
DIFFERENCE BETWEEN O/W AND W/O
EMULSIONS (Contin)…
Water in oil emulsion








Oil is the dispersion medium and water is the dispersed phase
For water soluble drug
Can be use to hydrate the upper layer of stratum corneum
(moisturizing cream)
Can increase the absorption of drug from these formulation
Can be used to clean skin from dirt
Oil soluble drugs are more quickly released from w/o emulsions
They are preferred for formulations meant for external use like
creams.
Not acceptable by consumer
Properties of emulsion
The basic properties which should be present in an emulsion
include:

appearance,

feel ,

odour ,

desirable viscosity,

consistency ,

effectiveness ,

stability .
These properties depends on the:
ingredients ,

type of emulsion,

ratio of the two phases ,

type and quantity of emulsifying agents ,

method of emulsification .

O/w emulsions will generally have a sheen or matte
surface as compared to w/o emulsions which have a
shiny or oily surface due to the presence of oil as
external phase .
W/o emulsios are oily and greasy in nature, not easily
removable from the surface of the skin whereas o/w
emulsions are non greasy and easily removable from
the skin surface .
The viscosity of the emulsions depends generally on the
viscosity of the continuous phase. As the ratio of
dispersed phase increases, the viscosity also increases to
a point where emulsion starts loosing its fluidity
Methods for preparing Emulsions for
Internal use
-1Trituration Method
This method consists of dry gum method and wet gum 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.

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.

-2Bottle 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.
Methods of Preparation of Emulsions:
1) Continental or Dry Gum Method:
"4:2:1" Method
4 parts (volumes) of oil
2 parts of water
1 part of gum
Acacia or other o/w emulsifier is triturated with oil in a perfectly
dry Wedgwood or porcelain mortar until thoroughly mixed.
Glass mortar has too smooth a surface to produce the proper size
reduction of the internal phase (Do not use glass mortar).
After the oil and gum have been mixed, the two parts of water are
then added all at once and the mixture is triturated immediately.
2) English or wet Gum Method:
Mucilage of the gum is prepared by triturating acacia
(or other emulsifier) with water.
The oil is then added slowly in portions, and the
mixture is triturated to emulsify the oil.
Should the mixture become too thick during the
process, additional water may be blended into the
mixture before another successive portion of oil is
added.
3) Bottle or Forbes Bottle Method:
Useful for extemporaneous preparation of emulsion from
volatile oils or oleaginous substance of low viscosity.
1- Put powdered acacia in a dry bottle.
2- Add 2 parts of oil
3- Thoroughly shake the mixture in the capped bottle.
4- A volume of water approximately equal to the oil is
then added in portions, the mixture being thoroughly
shaken after each addition.
This method is not suitable for high viscous oils
Points to be considered during formulations
of emulsions







Stability of the active ingredient
Stability of the excipients
Visual appearance
Color
Odor (development of pungent odor/loss of
fragrance)
Viscosity, extrudability
Loss of water and other volatile vehicle
components
Points to be considered… (Continued)







Concentration of emulsifier
Order of addition of ingredients Particle size
distribution of dispersed phases
pH
Temperature of emulsification
Type of equipment
Method and rate of cooling
Points to be considered… (Continued)




Texture, feel upon application (stiffness,
grittiness, greasiness, tackiness, spreadibility)
Microbial contamination/sterility (in the
unopened container and under conditions of
use)
Release/bioavailability (percutaneous
absorption)
Phase distribution, Phase Inversion
(homogeneity/phase separation)
Quality control tests for Emulsions
.1Determination of particle size and particle
count :
It is performed by optical microscopy,
sedimentation by using Andreasen apparatus
and Coulter counter apparatus.
.2Determination of phase separation :
Phase separation may be observed visually or by
measuring the volume of the separated phases.
Quality control tests….(Contin)..
.3Determination of viscosity :

The viscometers which should be used include cone and plate
viscometers. Capillary and falling sphere type of viscometrs
should be avoided.

For viscous emulsions, the use of penetrometer is recommended
as it helps in the determination of viscosity with age .

In case of o/w emulsions, flocculation of globules causes an
immediate increase in viscosity. After this change, the
consistency of the emulsion changes with time.

In case of w/o emulsions, the dispersed phase particles flocculate
quite rapidly resulting in a decrease in viscosity, which stabilizes
after 5 to 15 days.

As a rule, a decrease in viscosity with age reflects an increase of
.particle size due to coalescence
Quality control tests….(Contin)..
.4Determination of electrophoretic properties :
Determination of electrophoretic properties like
zeta potential is useful for assessing flocculation
since electrical charges on particles influence
the rate of flocculation.
O/W emulsion having a fine particle size will
exhibit low resistance but if the particle size
increase, then it indicates a sign of oil droplet
aggregation and instability.
Instabilities In Emulsions

An emulsion is a thermodynamically unstable
preparation so care has to be taken that the
chemical as well as the physical stability of the
preparation remains intact throughout the shelf
life .

There should be no appreciable change in the
mean particle size or the size distribution of the
droplets of the dispersed phase and secondly
droplets niamer dluohs esahp desrepsid eht fo
uniformly distributed .metsys eht tuohguorht
Emulsion Destabilization




Creaming
Flocculation
Coalescence
Combined methods
Instabilities In Emulsions…(Con)..
-1Creaming

An emulsion is said to cream when the oil or fat rises to
the surface, but remains in the form of globules, which
may be redistributed throughout the dispersion medium
by shaking.

An oil of low viscosity tends to cream more readily
than one of high viscosity.

Increasing the viscosity of the medium decreases the
tendency to cream.

Creaming is a reversible phenomenon which can be
corrected by mild shaking .
Creaming
Buoyancy
(Archimedes)
vs 
Friction
(Stokes-Einstein)
d g
2
18c
 Continuous phase viscosity
 density difference
g Acceleration due to gravity
d droplet diameter
v droplet terminal velocity
vs Stokes velocity
Instabilities In Emulsions…(Con)..
The factors affecting creaming are best described by
strokeâs law:
V= 2r9/g (2d-1d(2 η
Where; V= rate of creaming
r=radius of globules
d
esahp desrepsid fo ytisned = 1
d
muidem noisrepsid fo ytisned = 2
g= gravitational constant
η = viscosity of the dispersion medium
The following approaches can be used for
decreasing Creaming

Reduction of globule size :
According to strokeâs law, rate of creaming is directly proportional to
the size of globules. Bigger is the size of the globules, more will be
the creaming. Therefore in order to minimize creaming, globule
size should be reduced by homogenization.

Increasing the viscosity of the continuous phase :
Rate of creaming is inversely proportional to the viscosity of the
continuous phase i.e. more the viscosity of the continuous phase,
less will the problem of creaming. The viscosity of the continuous
phase should be increased by adding suitable viscosity enhancers
like gum acacia, tragacanth etc.
Instabilities In Emulsions…(Con)..
-2Cracking
Occasionally, it happens that an emulsion cracks during
preparation, i.e., the primary emulsion does not become
white but acquires an oily translucent appearance. In
such a case, it is impossible to dilute the emulsion
nucleus with water and the oil separates out.
Cracking of emulsion can be due to:





addition of an incompatible emulsifying agent ,
chemical or microbial decomposition of emulsifying agent ,
addition of electrolytes ,
exposure to increased or reduced temperature,
change in pH.
Instabilities In Emulsions…(Con)..
-3Phase Inversion



In phase inversion o/w type emulsion changes into w/o type
and vice versa .
It is a physical instability .
It may be brought about by the addition of an electrolyte or by
changing the phase volume ratio or by temperature changes .
Phase inversion can be minimized by:



using the proper emulsifying agent in adequate
concentration ,
keeping the concentration of dispersed phase
between 30 to % 60
storing the emulsion in a cool place.
Instabilities In Emulsions…(Con)..
4- Breaking:



Separation of the internal phase from the
external phase is called BREAKING of the
emulsion.
All or part of the liquid of the internal phase
becomes "unemulsified on the top or bottom of
the emulsion.
This is irreversible
Instabilities In Emulsions…(Con)..
5- Aggregation:


The internal phase tends to form aggregates of
globules.
Large globules or aggregates of globules rise
to the top or fall to the bottom of the emulsion
to form a concentrated layer of the internal
phase.
Flocculation and Coalescence
FLOCCULATION
COALESCENCE
Rheology of Flocculated
Emulsions



rg
Flocculation leads to an
increase in viscosity
Water is trapped within
the floc and must flow
with the floc
Effective volume fraction
increased
Gelled Emulsions
Thin liquid
Viscous liquid
Gelled solid
Creaming & Slight Flocculation
• Flocs have larger
effective size
• Smaller 
• Tend to cream much
faster
Creaming & Extreme Flocculation
• Heavily flocculated
emulsions form a
network
• Solid-like properties
(gel)
• Do not cream (may
collapse after lag
period)
Preservation Of Emulsions
-1Preservation from microorganisms:
It is necessary to preserve the emulsions from
microorganisms as these can proliferate easily in
emulsified systems with high water content, particularly
if carbohydrates, proteins or steroidal materials are also
present.
Contamination due to microorganisms can result
in problems such as:




color and odor change ,
gas production ,
hydrolysis ,
pH change ,
and eventually breaking of emulsion
An ideal preservative

should be nonirritant, nonsensitizing and nontoxic in the
concentration used .

It should be physically as well as chemically compatible with other
ingredients of the emulsions and with the proposed container of
the product .

It should not impart any taste, color or odor to the product.

It should be stable and effective over a wide range of pH and
temperature.

It should have have a wide spectrum of activity against a range of
bacteria, yeasts and moulds .

The selective preservative should have high water solubility and a
low oil/water partition coefficient .

.It should have bactericidal rather than bacteriostatic activity
Examples of antimicrobial preservatives
used to preserve emulsified systems:






parahydroxybenzoate esters such as methyl, propyl
and butyl parabens ,
organic acids such as ascorbic acid and benzoic acid,
organic mercurials such as phenylmercuric acetate
phenylmercuric nitrate ,
quarternary ammonium compounds such as
cetrimide,
cresol derivatives such as chlorocresol
miscellaneous agents such as sodium benzoate,
chloroform and phenoxyethanol.
Preservation Of Emulsions… (Con).
-2Preservation from oxidation:
Oxidative changes such as rancidity and spoilage due to
atmospheric oxygen and effects of enzymes produced
by micro-organisms is seen in many emulsions
containing vegetables and mineral oils and animal
fats .

Antioxidants are agents having a high affinity for
oxygen and compete for it with labile substances in
the formulation .
The ideal antioxidant should be





nontoxic,
nonirritant ,
effective at low concentration under the expected
conditions of storage and use,
soluble in the medium and stable .
Antioxidants for use in oral preparation should also
be odorless and tasteless.
Some of the commonly used antioxidants for
emulsified systems include:



alkyl gallate such as ethyl, propyl or dodecyl gallate ,
butylated hydroxyanisole (BHA ,)
butylated hydroxytoluene (BHT)
Stability testing
Stability testing of emulsions involves determining
stability at long term storage conditions,
accelerated storage conditions, freezing and
thawing conditions. Stress conditions are
applied in order to speed up the stability testing .
The stress conditions used for speeding up instability of
emulsions include:
 Centrifugal force
 Agitational force
 Aging
 Temperature
The following physical parameters are evaluated
to assess the effect of any of the above stress
conditions:




Phase separation
Viscosity
Electrophoretic properties
Particle size and particle count
Packaging, Labelling And Storage Of
Emulsions




Depending on the use, emulsions should be
packed in suitable containers .
Emulsions meant for oral use are usually packed
in well filled bottles having an air tight closure .
Light sensitive products are packed in amber
coloured bottles .
For viscous emulsions, wide mouth bottles
should be used .
Packaging, Labelling And Storage Of
Emulsions



The label on the emulsion should mention that
these products have to be shaken thoroughly
before use.
External use products should clearly mention
on their label that they are meant for external
use only .
Emulsions should be stored in a cool place but
refrigeration should be avoided as this low
temperature can adversely effect the stability
of preparation
Routes of administration of emulsions
Oral Emulsions :
Generally o/w emulsions are used for internal use as the
oil is more readily absorbed in a fine state of
subdivision through the gastro intestinal tract and
secondly the preparation becomes more palatable
when water forms the continuous phase, as the
medicinal oil is enveloped in a thin film of emulgent
which masks the bitter and oily taste of the drug like
liquid paraffin .
Orally emulsions are also used to facilitate the absorption
of the oil soluble drugs like vitamins A,D, E and K.
Liquid Paraffin Oral Emulsion







Liquid Paraffin 500 ml
Methyl cellulose 20 g
Vanillin 0.5 g
Chloroform 2.5 ml
Benzoic acid solution 20 ml
Saccharin sodium 0.05 g
Purified Water q.s 1000ml
Uses: Laxative. It acts as an emollient purgative in
chronic constipation especially during pregnancy
and old age.
Castor oil Emulsion



Castor oil 16 ml
Gum acacia q.s
Water 80 ml
Uses: Purgative
Cod-Liver oil Emulsion




Cod-liver oil 30ml
Syrup 12 ml
Ferric ammonium citrate 4 g
Cinnamon water q.s. 90 ml
Uses: Source of vitamin A and D .
Topical Emulsions:





For external use, emulsions may be either o/w or w/o
type .
Emulsions finds the maximum use in topical preparations ,
both for therapeutic and cosmetic use.
Therapeutically they are used as carrier for a drug .
In cosmetic industry o/w emulsions have been used for
formulation of moisturing lotions, hand lotions and make
up foundation lotions .
When oily layers are desired to prevent moisture loss
from the surface of skin, for barrier action and for
cleansing action, then w/o emulsions are formulated like
.cold creams
Antiseptic cream





Cetrimide 1g
Cetostearyl alcohol 10 g
White soft paraffin 10 g
Liquid paraffin 29 g
Purified water 50 g
Uses: Antiseptic cream for the treatment of
cuts, wounds and burns.
Cold Cream






Liquid paraffin 20 g
Hard paraffin 4.5 g
Lanette wax 3.5 g
Glycerine 4.5 g
Water 17.5 g
Propyl paraben 0.1 g
Uses: Skin protective and skin smoothner.
Briefing
Types Of Emulsions




Oil in water emulsions
Water in oil emulsions
Multiple emulsions
Microemulsions
Oil in water Emulsions (O/W:)






In this emulsion oil is the dispersed phase and water is the
dispersion medium .
The common example is milk .
These emulsions are used mainly for internal/oral use as
bitter or disagreeable taste and odor of drugs can be
masked by emulsification .
Externally these emulsions are used for formulating non
greasy creams, lotions and liniments .
Cosmetic products prepared using o/w emulsions can
easily be removed from the surface of the skin
Example: Castor oil emulsion, foundation creams,
vanishing creams.
Oil in water Emulsions (O/W:)
Water in oil Emulsions (W/O:)




In this emulsion water is the dispersed phase or the
internal phase and oil is the dispersion medium or the
external phase .
They are mainly used externally as lotions and creams
as the external layer of oil forms an occlusive layer and
prevents the evaporation of moisture from the surface
of the skin .
They are also effective as cleansing cream as they
solubilize the oil soluble dirt from the surface .
Example: Cold creams.
Water in oil Emulsions (W/O:)
Multiple Emulsions:


In this emulsion, oil in water (o/w) or water in oil
emulsion (w/o)s is dispersed in another liquid medium
to produce oil in water in oil (o/w/o) emulsion or water in
oil in water (w/o/w) emulsion.
Multiple emulsions are primarily used for formulating
sustained release dosage forms as the drug entrapped
in the innermost layer has to pass through the other two
phases before being released for absorption.
Water in oil in water (W/O/W)
multiple emulsion
Oil in water in oil (O/W/O (
multiple emulsion
Microemulsions:




Microemulsions are thermodynamically stable clear
isotropic solution of oil, water and amphiphile
(Emulsifying agent.)
They are homogeneous in nature .
They contain globules having a diameter ranging from
0.1 to 100 micrometers .
These emulsions appear as transparent solutions and
are more acceptable physically as compared to
conventional emulsions.
Advantages of Emulsions
.1They can mask the bitter taste and odor of
drugs, thereby making them more palatable. e.g.
castor oil, cod-liver oil etc.
.2They can be used to prolong the release of the
drug thereby providing sustained release
action.
.3Essential nutrients like carbohydrates, fats and
vitamins can all be emulsified and can be
administered to bed ridden patients as sterile
intravenous emulsions.
Advantages of Emulsions
.4Emulsions provide protection to drugs which
are susceptible to oxidation or hydrolysis.
.5Intravenous emulsions of contrast media have
been developed to assist in diagnosis.
.6Emulsions are used widely to formulate
externally used products like lotions, creams,
liniments etc.
Clinical Uses of Emulsions
1. Oral (Liquid administration of oils, eg.
Vitamins A, D, and E) Reasons of use:




No oily mouth-feel (if an o/w emulsion is
used).
Better taste than if completely solubilized.
May be more bioavailable.
Solubilized drug may be more bioavailable
Clinical Uses of Emulsions
2. Parenteral Drug Solubilization:


Emulsification of oils.
Emulsification of lipids for parenteral nutrition.
Clinical Uses of Emulsions
3. Topical

O/W emulsions: Drug suspended or solubilized
in the oil phase; less greasy than petrolatum type
bases; no occlusion.

W/O emulsions: some occlusive effect but
slightly less greasy than the petrolatum bases.
Tests Used To Identify Emulsion Type

Dilution test
Conductivity Test
Dye Solubility Test
Fluorescence Test
If an emulsion on exposure to ultra-violet
radiations shows continuous florescence under
microscope, then it is w/o type and if it shows
only spotty fluorescence, then it is Oil in o/w
type
Cobalt Chloride Test
When a filter paper soaked in cobalt chloride
solution is added to an emulsion and dried,
it turns from blue to pink, indicating that
the emulsion is o/w type.
Types of emulsifying agents:
1) Surface active agent:
forming a monomolecular film
2) Hydrophilic colloids:
forming a multimolecular film
3) Finely divided solid particles:
forming a particulate film
Surface active agent:
Hydrophilic colloids:
Finely divided solid particles:
Emulsions Preparation Methods
-1Trituration Method


Dry Gum Method
Wet Gum Method
-2Bottle Method
Emulsions Quality control tests
.1Determination of particle size and particle
count :
.2Determination of phase separation
.3Determination of viscosity
.4Determination of electrophoretic properties
Hope you be a good
Emulsion Maker