2. DEFINATION :
• Emulsion is thermodynamically unstable mixture of two
essentially immiscible liquids .
OR
• Emulsion is a dispersion in which the dispersed phase is
composed of small globules of a liquid distributed
throughout a vehicle in which it is immiscible and
stabilized by emulsifying agent .
• one phase persists in droplet form called internal or
discontinuous or disperse phase and is surrounded by
an external or continuous phase .
4. Simple emulsion :
• Oil-in-water emulsion : Oil is internal phase and water is
external phase . Eg;Terpentine liniment
• Water-in-oil emulsion : water is internal phase and oil is
external phase . Eg;Butter
Multiple emulsion :
• Multiple emulsions are complex polydispersed systems where
both oil in water and water in oil emulsion exists
simultaneously which are stabilized by lipophillic and
hydrophilic surfactants respectively .
5. Microemulsion : Micro emulsions are clear,
thermodynamically stable, isotropic liquid mixtures of
oil, water and surfactant, frequently in combination with
a cosurfactant. The aqueous phase may contain salt(s)
and/or other ingredients, and the "oil" may actually be a
complex mixture of different hydrocarbons.
• Particle size = 10-120nm
• Viscosity : Less viscous compare to simple emulsion .
6. IDENTIFICATION TEST :
TEST OBSERVATION
Dilution test O/W emulsion diluted with water and W/O emulsion
diluted with oil .
Dye test Water-soluble(Amaranth) dye will dissolve in the
aqueous phase. Oil-soluble dye(scarlet red) will dissolve
in the oil phase.
CoCl2 filter paper test Filter paper deep into CoCl2 solution and dried (blue) .
Deep into emulsion, it gives pink color when O/W
emulsion is their .
Fluorescence test Under UV light,O/W exhibit dot pattern and W/O give
fluorescence throughout .
Conductivity test Electric current conducted by O/W emulsion.
7. THEORY OF EMULSIFICATION :
1 . Surface tension theory :
• According to the surface tension theory of
emulsification, the use of emulsifiers and stabilizers
lowers the interfacial tension of the two immiscible
liquids .
• Reducing the repellent force between the molecules.
Thus, the surface-active agents facilitate the breaking up
of large globules into smaller ones, which then have a
lesser tendency to reunite or coalesce.
8. 2 . Oriented-Wedge Theory :
• Mono molecular layers of emulsifying agents are cover
the droplet of the internal phase of the emulsion
• It is based on the presumption that certain emulsifying
agents orient themselves within a liquid according to
their solubility in that particular liquid .
9. 3 . Interfacial film theory :
• Emulsifying agent form thin film surrounding the
droplets of the internal phase .
• The film prevents the contact and the coalescence of the
dispersed phase .
11. EMULSIFYING AGENT :
• They are the substances added to an emulsion to
prevent the coalescence of the globules of the dispersed
phase. They are also known as emulgents or emulsifiers.
• They help in formation of emulsion by three
mechanisms.
- Reduction in interfacial tension
- Formation of a rigid interfacial film
- Formation of an electrical double layer
12.
13. • Characteristics :
Be stable .
Be compatible with other ingredients .
Be non – toxic .
Possess little odor , taste , or color .
Not interfere with the stability of efficacy of the
active agent .
14. Classification of Emulsifier :
1 . Synthetic :
Anionic surfactants :
• Negatively charged in aqueous solution .
• Widely used because of cost and performance
• Sodium lauryl sulfate commonly used to form O/W emulsion .
• Alkali hydroxide + Fatty acid Alkali metal soap (Sodium
oleate)
• Alkali earth metal soap (calcium oleate) produce stable W/O
emulsion because of low water solubility .
• Triethanolamine stearate produce stable O/W emulsions .
16. Non-ionic surfactants :
• Consist of (CH2CH2O)noH or OH as hydrophilic group and
exhibit variety of HLB which stabilize O/W or W/O
emulsions .
• Useful for oral and parenteral formulation bcz of their
low irritation and toxicity .
• Neutral nature so less sensitive to change pH of medium
and presence of electrolytes .
• Produce equally balanced HLB of hydrophilic and
hydrophobic surfactants .
17. • Eg; Span – not soluble in water and used for W/O
emulsions .
• Eg; Tween – soluble in water and used for O/W
emulsions .
18. Ampholytic surfactants :
• Possess both cationic and anionic groups in the same
molecule and dependent on pH of the medium .
• Lecithin is used for parenteral emulsion .
19. 2 . Auxiliary emulsifiers :
• Auxiliary emulsifying agents include those compounds
that are normally incapable themselves of forming
stable emulsion. They as thickening agents and help to
stabilize the emulsion .
20.
21. 3 . Natural emulsifier :
• Derived from plants and animal and hydrated lipophilic
colloids (hydrocolloids)
• No effect on interfacial tension
• Protective colloidal effect
22. Hydrocolloids :
• Form multimolecular film
• Promote O/W emulsion
• Do not cause appreciable lowering of surface tension
• Increase viscosity
24. Finely Divided Solids :
• Good emulsifier in combination with surfactants and/or
macromolecules that increase viscosity .
• Eg; Polar inorganic solid – Heavy metal hydroxide, non-
swelling clays and pigments . Polar solids wetted by
water in greater extent than oil phase .
Colloidal Clays : Bentonite,Veegum ,Magnesium
trisilicate
Metallic hydroxides : Magnesium hydroxide ,Aluminium
hydroxide
• Eg; Non-polar solid – Carbon or Glyceryl tristearate .
Non-polar solids wetted by oil phase .
25. VISCOSITY MODIFIER
• For W/O emulsions polyvalent metal soaps or high
melting waxes and resins in oil phase can be used to
increase viscosity .
• Greater volume of internal phase, greater viscosity .
• To control emulsion viscosity, 2 interacting effects must
be balanced .
1. Viscosity of O/W and W/O emulsion can increased by
reducing particle size of dispersed phase .
2. Flocculation or clumping which increase viscosity .
• Viscosity also increase with increse in age .
26. ANTIMICROBIAL PRESERVATIVES :
• Emulsion contain carbohydrates, proteins, sterols,
phosphatides which support growth of microorganism .
So that , preservatives necessary .
• Cause :
During production
During use
Poor quality raw material
Machine contamination
water
27. • Characteristics :
Less toxic
Stable to heat and storage
Chemically compatible
Reasonable cost
Acceptable taste, odor and color.
Effective against fungus, yeast, bacteria.
Available in oil and aqueous phase at effective level concentration.
Preservative should be in unionized state to penetrate the bacteria.
Not bind to other components of the emulsion .
28. • Eg ;
TYPE EXAMPLE CHARACTERISTICS
Acid and acid
derivatives
Benzoic acid and salts
Propionic acid and salts
Dehydroacetic acid
Antifungal agen
Alcohols Chlorobutanol
Phenoxy-2-ethanol
Eye preparation
Aldehyde Formaldehyde
Glutaraldehyde
Broad spectrum
Phenols Phenol
Cresol
Broad spectrum
Mercurials Phenylmercuric acetate Broad spectrum
29. ANTIOXIDENT
• Many drugs incorporated into emulsions are subjected
to autoxidation and resulting decomposition .
• Upon autoxidation, vegetable oils give rise to unpleasant
odour, appearance and taste .
• Autoxidation is free radical chain oxidation reaction . It
can be inhibited by absence of oxygen or free redical
chain breaker or by reducing agent .
32. FLOCCULATION :
• Flocculation is reversible aggregation of droplets of the
internal phase . It take place before, during and/or after
creaming .
• Cause of flocculation ; Insufficient amount of emulsifier .
• Types of flocculation depends on strength of interaction
between particles which is determined by ; chemical
nature of emulsifier, phase volume ratio, concentration
of dissolved substance especially electrolytes and ionic
emulsifiers .
• Eg; 2% hexadecane-in-water emulsion stabilized with
0.09% Aerosol , which is negatively charged surfactant,
remains deaggregated .
33. • A high internal phase volume, i.e. tight packing of
dispersed phase, tends to promote flocculation .
• The extent of flocculation of globules depends on ;
(a) globule size distribution.
(b) charge on the globule surface.
(c) viscosity of the external medium.
34. (a) Globule size distribution
• Uniform sized globules prevent flocculation.
• This can be achieved by proper size reduction process.
(b) Charge on the globule surface
• A charge on the globules exert repulsive forces with the
neighboring globules.
• This can be achieved by using ionic emulsifying agent, electrolytes
etc.
(c) Viscosity of the external medium.
• If the viscosity of the external medium is increased, the globules
become relatively immobile and flocculation can be prevented.
• This can be obtained by adding viscosity improving agents (bodying
agents or thickening agents) such as hydrocolloids or waxes.
35. CREAMING :
• Creaming is the upward movement of dispersed droplets of
emulsion relative to the continuous phase (due to the density
difference between two phases).
• Creaming is the concentration of globules at the top or bottom of
the emulsion.
• Droplets larger than 1 mm may settle preferentially to the top or
the bottom under gravitational forces.
• Creaming may also be observed on account of the difference of
individual globules (movement rather than flocs).
• It can be observed by a difference in color shade of the layers.
• It is a reversible process, i.e., cream can be re-dispersed easily by
agitation, this is possible because the oil globules are still
surrounded by the protective sheath of the emulsifier.
36. • Creaming results in a lack of uniformity of drug
distribution. This leads to variable dosage. Therefore,
the emulsion should be shaken thoroughly before use.
• Creaming is of two types, upward creaming and
downward creaming .
A B
37. A . Upward creaming, is due to the dispersed phase is less
dense than the continuous phase. This is normally
observed in o/w emulsions. The velocity of
sedimentation becomes negative.
B . Downward creaming occurs if the dispersed phase is
heavier than the continuous phase. Due to gravitational
pull, the globules settle down. This is normally observed
in w/o emulsions.
38. • Creaming is influenced by,
Globule size
Viscosity of the dispersion medium
Difference in the densities of dispersed phase and dispersion medium.
• Creaming can be reduced or prevented by:
1. Reducing the particle size by homogenization. Doubling the diameter of oil
globules increases the creaming rate by a factor of four.
2. Increasing the viscosity of the external phase by adding the thickening
agents such as methyl cellulose, tragacanth or sodium alginate.
3. Reducing the difference in the densities between the dispersed phase and
dispersion medium.
39. COALESCENCE :
• Coalescence is a growth process during which the emulsified
particles join to form larger particles . This indicates that
emulsion will separate completely or BREAK .
• Coalescence in flocculated or unflocculated emulsion
prevented by mechanical strength of interfacial barrier .
• Coalescence is observed due to:
Insufficient amount of the emulsifying agent.
Altered partitioning of the emulsifying agent.
Incompatibilities between emulsifying agents.
40. Brecking :
• Breaking is the destroying of the film surrounding the
particles.
• Separation of the internal phase from the external phase is
called breaking of the emulsion.
• This is indicated by complete separation of oil and aqueous
phases, is an irreversible process, i.e., simple mixing fails. It is
to re-suspend the globules into an uniform emulsion.
• In breaking, the protective sheath around the globules is
completely destroyed and oil tends to coalesce.
41. PHASE INVERSION :
• This involves the change of emulsion type from o/w to
w/o or vice versa.
• When we intend to prepare one type of emulsion say
o/w, and if the final emulsion turns out to be w/o, it can
be termed as a sign of instability.
43. PHASE SEPARATION
• The rate of phase separation after aging may be
observed visually or by measuring volume of separated
phase .
• The amount of coalescence depends on concentration
of emulsifier . If concentration raised to 2 or 5%, amount
of visible coalescence is negligible even after 2 yrs
storage .
• Phase separation determined by withdrawing small
amount of emulsion from top and bottom after some
period of storage and comparing composition of two
samples by analysis of water content, oil content .
44. VISCOSITY
• Viscosity measured by Brookfield viscometer.
• Viscosity increase with increase in age of emulsion .
• To achieve proper viscosity , vicosity modifier is added .
45. ZETA POTENTIAL
• Zeta potential measured by observing the movement of
particles under the influence of electric current .
• Zeta potential used to determine emulsion instability due to
flocculation .
• The measurement of electrical conductivity of o/w or w/o
emulsions determined with the aid of Pt electrodes .
• The conductivity depends on degree of dispersion . o/w
exhibit low resistence .
• If resistence increase then it is sign of aggregation and
instability .
46. PARTICLE SIZE
• Particle size of emulsion is measured by ;
• Microscopic method
• Coulter counter
• Electronic counting device
• Light scattering
49. APPLICATION
• Oral, rectal and topical administration of oils and oil-soluble
drugs.
• The unpleasant taste or odor can be masked by emulsification
• The absorption and penetration of medicament are enhanced
by emulsification
• Intramuscular injections of water soluble drugs or vaccine to
provide slow release
• The use of sterile stable i.v emulsion containing fats,
carbohydrates and vitamins as a potential nutrition .
50. PACKAGING
• 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.
• 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.
