Emulsion, Types, Identification tests, Components, Emulsifying agents, Theories of emulsification, Formulation, HLB system, Stability Issues, Drug release in GIT, Advantages, Disadvantages

1. Emulsions
Introduction,Types,Formulation,Stability

2. Introduction
• An emulsion is a two phase system consisting of two
immiscible liquids, one of which is dispersed as finite
globules in the other.
• An emulsifying agent is needed to join the phases.

3. TYPES OF EMULSION
Oil in Water, Water in Oil emulsions

4. Types
• Major types of emulsions are:
 Oil in Water emulsions: Oil is dispersed as small
globules in water. Such emulsions are usually used for
oral administration as well as for IV and topical uses.
 Water in Oil emulsions: Water is dispersed as small
globules in oil. Such types of emulsions are usually
used externally.
 Other types include Multiple Emulsions and Micro
Emulsions.

5. IDENTIFICATION
Tests to determine type of emulsion

6. Identification tests
• Some tests for the identification of emulsion system are
given below:
• Dilution Test: If we add more of the continuous phase,
the emulsion is only diluted and no other effect occurs
on it.
• Conductivity Method: O/W emulsion can conduct
electricity as water is a good conductor of electricity.
• Dye Solubility Test: Water-soluble dye is added to it
and examined under microscope.

7. Identification tests
• Cobalt Chloride Test: CoCl2 turns from blue to pink
when exposed to water.
• Fluorescence Test: Many oils have the property to
show florescence under UV light.
• Creaming Direction Test: If the densities of both
water phase and oil phase are known, we can identify
the emulsion type on the basis of creaming direction.

8. EMULSIFYING AGENTS
Introduction, Types

9. Emulsifying agents
• They are very important for the stability of emulsions.
• An ideal emulsifying agent has the following properties.
• Surface Activity: It should have the ability to reduce
the surface tension to less than 10 dyne/cm.
• Charge Production: The emulsifier must form charges
on the surface of the globules. It prevents coalescence.
• Viscosity Enhancement: The emulsifier should have
the ability to increase the viscosity of the emulsion.
• Effectiveness: The emulsifying agents must be
effective in smaller concentration.

10. Types of Emulsifiers
• Emulsifiers are classified as:
• Synthetic emulsifier
• Natural emulsifier
• Auxiliary emulsifier
• Finely divided solid emulsifiers

11. Synthetic Emulsifiers
• The synthetic emulsifiers are advantageous because
they are non susceptible to the microbial growth; and a
variety of emulsifiers may be obtained by modifications.
• The synthetic emulsifying agents may be classified into
Non-Ionic & Ionic Emulsifiers.

12. Non-ionic Emulsifiers
• Non-ionic emulsifiers contain the largest group of
emulsifying agents.
• The examples of Non Ionic Emulsifiers are Glycerol
esters, Fatty acid esters, Sorbitan mono laurate, etc.
• The non-ionic emulsifiers are of great advantages
because these are not affected by pH change or
presence of strong electrolytes.
• The disadvantage is that preservatives having Phenolic
or Carboxylic acid groups are inactivated by them.

13. Ionic Emulsifiers
• The ionic emulsifiers include:
• Anionic Emulsifiers: They are not suitable for oral use
because of unpleasant taste and GIT irritant action.
The examples of anionic emulsifiers are Alkali soaps,
Metallic soaps, Sulphonates, etc.
• Cationic Emulsifiers: Cationic agents are weak
emulsifiers. Example is Benzalkonium Chloride.

14. Natural Emulsifiers
• There are a lot of emulsifying agents that are derived
from plants and animal sources.
• These substances are so much complex and have a
variable chemical composition and thus they show a
very wide change in the emulsifying properties.
• They can easily be destroyed by microorganisms.
• Examples are Acacia, Gelatin, lecithin, Cholesterol and
wool fat, etc.

15. Auxiliary Emulsifiers
• Auxiliary emulsifiers are not capable to form a stable
emulsions by themselves but when they combine with
primary emulsifiers, they give a highly stable emulsion.
• Auxiliary emulsifiers are thickening agents and prevent
the creaming and sedimentation and thus make the
emulsion stable.
• Examples includes Tragacanth, Agar, etc.

16. Finely divided solids
• There are certain solid that acts as emulsifiers when
they are ground to powder form.
• The examples of such solids are Bentonite, Magnesium
hydroxide, Silica gel, etc.

17. Selection
• It should be non-toxic and non-irritant; physically and
chemically compatible.
• It should not give any color, taste, or odor to the
product.
• It should be capable of maintaining and producing the
desired viscosity of the product.

18. HYDROPHILIC-LIPOPHILIC
BALANCE SYSTEM
HLB value & its uses

19. HLB system
• It is a system having numerical values from 1 to 50,
• It tells us whether emulsifier is hydrophilic or lipophilic.
• HLB value can be determined as:
HLB = 20 ×
𝑀ℎ
𝑀
• If the HLB value is 3-8 then the emulsifier will be
lipophilic.
• If the HLB value is 8-18 then the emulsifier will be
hydrophilic.

20. HLB system
HLB values of some emulsifiers

21. HLB system
Advantages
• It helps to identify
lipophilic or hydrophilic
emulsifiers.
• Two emulsifiers can be
blended to bring them at
any HLB value.
Disadvantages
• It does not tell required
quantity of emulsifier.
• Different methods give
different HLB value for
the same emulsifier.

22. THEORIES OF
EMULSIFICATION
Surface tension theory, Oriented-Wedge theory, Interfacial film
theory

23. Emulsification
• When a liquid is broken into small droplets, the surface
free energy also increases.
• Thus, the system separates into two phases due to
coalescence of oil particles.
• Emulsifying agents reduce the interfacial tension
between the two phases and form a stable interfacial
film between them.
• Three theories of emulsification describe this
phenomena.

24. Theories of Emulsification
• Surface Tension theory: Emulsifier lower the
interfacial tension of the two immiscible liquids,
reducing the repellent force between the liquids, and
diminishing each liquid attraction for its own molecules.
• Oriented Wedge theory: Emulsifying agent orients
itself in that liquid phase of an emulsion in which it is
more soluble. It is based on Bancroft rule.
• Interfacial Film theory: Emulsifying agent is adsorbed
at the interface between the oil and water, surrounding
the droplets of the internal phase as thin layer of film.
The tougher and more pliable the film, the greater will
be the stability of the emulsion.

25. PRESERVATION
Antimicrobial preservatives, Antioxidants

26. Antimicrobial preservatives
• The preservative must be non-toxic, stable, cheap,
broad spectrum, non ionized and chemically
compatible. It should have acceptable taste, odor and
color.
• It should be bactericidal.
• Examples are Benzyl alcohol, cetrimide, cresol, Phenol
etc.

27. Antioxidants
• Autoxidation occurs by free radical reaction. It can be
prevented by absence of oxygen, a free radical chain
breaker by reducing agent.
• An antioxidant should be nontoxic, nonirritant, effective,
soluble in the medium and stable.
• Antioxidants for use in oral preparation should be
odorless and tasteless.
• Examples are Ascorbic acid, Sulphites, L-tocopherol.

28. ADDITIVES
Colouring & Flavouring agents

29. Colouring & Flavouring agents
• Colour is rarely needed in an emulsion, as most have
an elegant white colour and thick texture.
• Emulsions for oral use will usually contain some
flavouring agent.

30. METHODS OF PREPARATION
Dry Gum method, Wet Gum method, Nascent soap method

31. Wet Gum Method
• It is also known as English Method or American
method.
• It is called wet gum method because the gum is wetted
by water.
• All water soluble ingredients are dissolved in aqueous
phase and oil soluble components are dissolved in oil.
• Then, dispersed phase is added gradually to the
continuous phase and is stirred continuously.
• It is the easiest and most frequently used method.

32. Dry Gum Method
• It is also known as Continental Method.
• It is the process in which the dry gum is distributed in
oil instead of water.
• The external phase is added to the internal phase.
• So, this can lead to the formation of W/O emulsion
although the emulsifier is Hydrophilic.

33. Nascent Soap Method
• In this method, oil containing free fatty acids is added to
water phase containing Ca(OH)2. This results in the
formation of alkali soap.

34. STABILITY ISSUES
Flocculation, Coalescence, Creaming, Cracking, Phase Inversion

35. Major Stability Issues of Emulsions
Flocculation, Coalescence, Creaming, Cracking, Phase Inversion

36. Flocculation
• It is the association of particle within an emulsion to
form large aggregates.
• Interfacial film and individual droplets remain intact. So,
these aggregates can easily be redispersed upon
shaking.
• The reversibility of flocculation depends upon strength
of interaction between particles as determined by:
o the chemical nature of emulsifier,
o the phase volume ratio,
o the concentration of dissolved substances, specially
electrolytes and ionic emulsifiers.

37. Flocculation
• The extent of flocculation of globules depends on
• Globule size distribution: Uniform sized globules
prevent flocculation. This can be achieved by proper
size reduction process.
• Surface charge: A charge on the globules exert
repulsive forces with the neighbouring globules. This
can be achieved by using ionic emulsifying agent,
electrolytes, etc.
• Viscosity: Flocculation can be prevented by increasing
viscosity of external medium. This can be obtained by
adding viscosity improving agents.

38. Creaming or Sedimentation
• Creaming and sedimentation is the concentration of
globules at the top or bottom of emulsion.
• It is governed by Stokes’ law:
V =
2𝑟2 𝜌1− 𝜌2 𝑔
9η
• Emulsion can be easily redispersed by shaking.
• Creaming is undesirable because:
o Increased possibility of coalescence
o Creamed emulsion is inelegant
o Risk of incorrect dose

39. Creaming or Sedimentation
• Creaming can be reduced by:
 Reducing globule size by homogenization
 Increasing viscosity of dispersion medium
 Reducing the difference in density

40. Coalescence
• Coalescence is the fusion of two or more droplets of
the disperse phase forming one droplet.
• Coalescence is an irreversible process and
redispersion cannot be achieved by shaking.
• Coalescence is observed due to:
o Insufficient amount of the emulsifying agent
o Altered partitioning of the emulsifier
o Incompatibilities between emulsifiers

41. Coalescence
• Increasing the viscosity will reduce the potential for
coalescence. It can be done by adding viscosity
enhancing agents, increasing percentages of oil phase,
decreasing the globule size, and using higher amounts
of solid fats.
• Using emulsifying agents will decrease the potential for
coalescence.
• Preventing extreme temperatures is important. Low
temperature may lead to cracking of film. An increased
temperature decreases the viscosity and increases
number of collisions between droplets.

42. Cracking
• Cracking means the separation of disperse and
continuous phase.
• Cracking may occurs due to following reasons:
o By addition of emulsifying agent of opposite type
o By decomposition or precipitation of emulsifying agent
o By addition of common solvent
o By microorganisms
o Change in temperature
o By creaming

43. Phase inversion
• This involves the change of emulsion type.
• The process is irreversible.
• Reasons of phase inversion can be:
o Increasing the dispersed phase concentration
o Adding substances that alter the solubility of emulsifier
o By changing the emulsifying agent
o Suppression of ionization for ionic surfactant
o Changing phase volume ratio
o Temperature changes

44. Phase inversion
• The phase inversion can be minimised by:
 Controlling concentration of disperse phase
 Storing the emulsion in cool place
 Using proper emulsifier in enough concentration

45. DRUG RELEASE
Factors affecting drug release in GIT

46. Major Factors
• The mechanism of drug release is dependent of
several factors.
• First, drug solubilization characteristics are
determining, principally the solubility in triglycerides
which form the chylomicron core.
• Decrease in the particle size leads to a better rate of
drug release.
• Oil nature also affect drug bioavailability. Vegetable
edible oils increase drug absorption contrary to mineral
oils. The oil chain length as well as the chain saturation
seem to be important.

47. Major Factors
• The nature and quantity of surfactant present in the
systems are very important. For absorption
enhancement and oil digestion inhibition, surfactant
with high HLB values are preferable.
• The charge effect of the emulsion influences oral
bioavailability. Cationic surfactant improve the
absorption profile due to electrostatic attraction.

48. APPLICATIONS
Advantages, Disadvantages

49. Advantages
• Emulsions are used to deliver water insoluble drugs.
• Oils having therapeutic effect can be administered.
• Emulsions can mask the bitter taste and odor of drugs.
• Emulsion gives stability to drugs stable in oily phase.
• Emulsion give sustained release of the drug.
• Essential nutrients can be emulsified and administered.
• IV emulsions of contrast media are used in diagnosis.
• Emulsions are used if patient cannot swallowing solid
dosage forms.
• Emulsions protect drugs from oxidation or hydrolysis.
• Emulsions are used widely to formulate externally used
products like lotions, creams, liniments, etc.

50. Disadvantages
• They are thermodynamically unstable.
• Emulsions may be difficult to manufacture.
• Storage conditions may affect stability.
• They are bulky, difficult to transport, and prone to
container breakages.
• They are liable to microbial contamination which can
lead to cracking.
• Uniform and accurate dose my not be achieved.