This presentation explains about emulsion.

1. EMULSION

2. EMULSION
• An emulsion is a dispersion of a liquid as globules in another liquid, both the liquid
being immiscible with each other.
Eg:- Dispersion of oil in water
Or
Dispersion of water in oil
• Diameter of the globules vary from 0.1 - 10 µm
• Globules diameter as small as 0.01 µm and as large as 100 µm are possible in some
emulsions.

3. TYPES OF EMULSION
• Fine emulsion – globule size 0.25 -25 micrometer –milky
• Micro emulsion -0.01 micrometer (5-50nm)-transparent
• Nanoemulsion :20-100nm
• Examples of emulsion :
• Oral emulsion usually o/w type
• Cold cream-w/o type emulsion
• Cosmetics-vanishing cream –o/w type
• Parenteral emulsion- fat soluble vitamin A D E and sex hormones
• Diagnostic emulsion –radio opaque emulsion for x ray

4. TYPES OF EMULSION
• 1. Oil in water type emulsion
(o/w)
• 2. Water in oil type emulsion

5. OIL IN WATER TYPE EMULSION
(O/W)
• Oil is distributed as globules throughout the aqueous continuous phase ,the
emulsion is called oil in water type emulsion
• Medicinal emulsions for oral administrations are usually o/w type
emulsion

6. TESTS FOR IDENTIFICATION
• Dilution test
• Conductivity test
• Dye test:
• Water soluble dye:amaranth,methylene blue (o/w)
• Oil soluble dye: sudan 3, scarlet red(w/o)
• Fluorescence test
• Direction of creaming test-creaming upward(o/w) & creaming downward(w/o)
• Cocl2 test(o/w)
• Filter paper test-(o/w)migrate faster in filter paper

7. FORMULATION OF EMULSION
• Reduces the interfacial tension between two phases and thus make them
miscible with each other and form a stable emulsion
• Also known as emulgent or emulsifiers

9. EMULSIFYING AGENT:-
• Irrespective of the chemical nature of the emulsifying agent they tend to
concentrate at the interface and form a tough film around the globules

10. Semi synthetic emulsifying agents
Anionic Organic sulfates: sodium lauryl sulfate
Organic sulfonates:sodium cetyl sulfate
Bile salts:sodium glycolate
alkali soap :pottassium stearate ,triethanolamine
acetate
Cationic Quarternary ammonium compounds:
benzalkonium chloride,benzethonium
chloride,cetrimide ,cetyl trimethyl ammonium
Pyridinium compounds: dodecyl pyridinium
chloride
Non ionic Glyceryl monostearate,sorbitan fatty acid esters
amphoteric lecithin

11. Non ionic surface active agents
hydrophobic Hydrophilic
Sorbitan fatty acids esters Tweens
(w/o emulsion) Polyoxyethylene mono laurate (tween 20)
Poly oxy ethylene mono myristate (tween 40)
Polyoxyethylene mono palmitate (tween 60)
Polyoxyethylene mono oleate (tween 80)
(o/w emulsion)

12. Hlb scale

13. Surfactants Hlb value
Acacia 8
Tragacanth 13.2
Sodium lauryl sulfate 40
Sodium oleate 18
Triethanolamine 12
Tween 20 16.7
Tween 60 14.9
Tween 80 15
Span 20 8.6
Span 60 4.7

14. FORMULATION OF EMULSION
• Bencraft rule describe the relationship between the nature of emulsifying
agent and the type of emulsion formed
• If surfactant is more soluble in water –o/w emulsion
• If surfactant is more soluble in oil –w/o emulsion

15. PREPARATION OF EMULSION
Small scale
• Wet gum method
• Dry gum method
• Bottle or forbes bottle method

16. Preparation of primary emulsion
Type of oil example o/w/gum
Fixed oil Arachis oil ,Almond oil, Castor oil ,
cod liver oil
4:2:1
Volatile oil Turpentine oil, pepper mint oil,
cinnamon oil
2:2:1
Mineral oil Liquid paraffin 3:2:1

17. PREPARATION OF EMULSION-LARGE SCALE
• Mechanical stirrer
• Homogenizer
• Ultrfine sonifiers
• Colloidal mills

18. PHYSICAL
STABILITY OF
EMULSION

19. PHYSICAL STABILITY OF EMULSION
• Stability of emulsion is characterised by
– Absence of coalescence of internal phase
– Absence of creaming
– Maintenance of elegance with respect to colour, odour, and other
physical properties
• The various instabilities of the emulsions are
• Flocculation and creaming
• Coalescence and breaking
• Phase inversion

20. PHYSICAL STABILITY OF EMULSION

21. FLOCCULATION
• In this case neighboring globules come closer to each other and form colonies
in the external phase.
• But the aggregation is not clearly visible.
• This is probably the initial stage that leads to instability.
• The extend of flocculation of globules depends on
• Globule size distribution
• Charge on the globule surface
• Viscosity of the external medium

22. FLOCCULATION
• Properly size reduced, uniform sized globules prevent
flocculation.
– Addition of emulsifying agent or electrolytes cause
charge on the surface of the globules.
– It exerts repulsive forces with the neighbouring
globules.
so flocculation is prevented

23. FLOCCULATION
– If viscosity of the dispersion medium is enhanced by the
addition of viscosity improving agents such as bodying agents
or thickening agents (hydrocolloids or waxes).
– The globules become immobile and flocculation can be
prevented.
• Flocs move slowly either upward or downward leads to creaming.

24. CREAMING
• Creaming is the concentration of globules at the top or bottom of
the emulsion.
• Due to the density difference in the two phases the floccules or
individual globules moves either upward or downward leading
to creaming.
• It can be observed by a difference in colour shade of the layers.
• Creaming is a reversible process.ie cream can be re dispersed
easily by agitation

25. CREAMING
• In creaming drug is not uniformly distributed, this leads to
variable dosage, therefore the emulsion should be shaken
thoroughly before use.
• Creaming is of two types
• Upward creaming
• Downward creaming

26. CREAMING
• Upward creaming
• Due to less denser internal phase
• Normally seen in o/w type emulsion
• Downward creaming
• If the internal phase is heavier due to gravitational pull the globules
settle down.
• Normally seen in w/o type emulsion
• Creaming involves movement of globules in an emulsion. So stokes
law is applicable.

27. CREAMING
• Therefore creaming is influenced by
– Globule size
– Viscosity of the dispersion medium
– Difference in the densities of the dispersed phase and dispersion
medium
• Creaming can be reduced or prevented by
– Reducing the particle size by homogenization.
– Doubling the diameter of oil globules, increases creaming rate by
a factor of four.

28. CREAMING
• Increasing the viscosity of the external phase, creaming
decreases
• Reducing the density difference between the dispersed phase
and dispersion medium creaming decreases. Generally the
density of aqueous phase is higher than the density of oil phase.
To make densities equal oil soluble substances
( bromonaphthalene, bromoform ) added to the oil phase so the
density of the oil phase increases. This technique is rarely used

29. COALESCENCE
– If the emulsifier film around the globule is broken or
destroyed in such cases globule tend to fuse with each other
and form bigger globules.
– Globule size is increased and the number of globules
decreases. It is an indication of coalescence.
– Coalescence is followed by creaming

30. COALESCENCE
– Coalescence is observed due to
– Microbial contamination
– Temperature changes
– Creaming
– Changes in phase volume ratio
– Insufficient amount of emulsifying agent
– Altered partitioning of the emulsifying agent
– Incompatibilities between emulsifying agent

31. COALESCENCE
• Prevention
 Maintaining a homogenous particle size throughout the
dispersed phase
 Increasing the viscosity to the optimum level, with the use of
suitable viscosity improvers
 Optimum dispersion of particles in the continuous phase
 Phase volume ratio -50:50
 Storing emulsion at a cool place

32. BREAKING
– This is indicated by complete separation of aqueous and oil
phase
– Irreversible process
• Protective sheath around the globule is completely destroyed

33. PHASE INVERSION
– This involves the change of emulsion type from o/w to w/o or
vice versa
– When we intended to prepare o/w type emulsion, but the final
emulsion turns to w/o type.
– It is a sign of instability

34. PHASE INVERSION
• Phase inversion may be caused by
• Changes in phase volume ratio
• Changes in temperature
• Coalescence
• Storage period
• Changes in nature of emulsifier

35. PHASE INVERSION
• Phase inversion can be prevented by
– Use of proper emulsifier in a suitable concentration
– Maintaining disperse phase below 74%
– Preventing coalescence which inturn prevents phase
inversion
– Storing the emulsion in a cool place

36. THEORIES RELATED TO STABILITY OF EMULSION ARE
– Brownian movement
– Stokes law

37. FACTORS WHICH IMPROVES PHYSICAL STABILITY
• Particle size
– As particle size reduced (0.01micrometer) they tent to
exhibit Brownian motion. So rate of creaming is
insignificant.
• Eg:-microemulsion
• According to stokes’ law the diameter of the globule is
considered as a major factor in creaming .

38. FACTORS WHICH IMPROVES PHYSICAL STABILITY
– According to stokes law, diameter halved, the rate of
creaming decreases four fold
Optimum globule size is required for maximum stability

39. FACTORS WHICH IMPROVES PHYSICAL STABILITY
• Particle size distribution
– In mono size or uniform size globules containing emulsion, the globules pack
loosely and globule to globule contact is less.
– So it imparts maximum stability.
– If the globules are of different size, globules of smaller size occupy the space
between the larger globules.
– Thus closed packing induces greater cohesion between the globules. Which
leads to coalescence

40. FACTORS WHICH IMPROVES PHYSICAL STABILITY
• Viscosity
– As the viscosity increases mobility of globules hindered. So flocculation of
globules reduced.
– Simultaneously the Brownian movement of globules also hindered leading to
creaming.
– Due to this antagonistic effect an optimum viscosity is desirable for good
stability.
– Thickening agents used for internal preparations are Tragacanth, veegum,
cellulose derivatives etc.
– External use
• Bees wax, stearic acid, sterayl alcohol

41. FACTORS WHICH IMPROVES PHYSICAL STABILITY
• Phase volume ratio
– In an emulsion the relative volume of water and oil is
expressed as phase volume raio.
– Medicinal emulsion – phase volume ratio 50 :50
• This proportion brings about loose packing of globules
• Uniform spherical globules in loose packing have porosity of
48% of the bulk volume. Remaining 52% occupied by
globules

42. FACTORS WHICH IMPROVES PHYSICAL STABILITY
– In an emulsion, the volume of internal phase should be less
than 74%
– The upper limit 74% of oil can be incorporated in to an
emulsion. But this may leads to breaking of the emulsion
– This value is referred to as critical point of phase volume
ratio

43. FACTORS WHICH IMPROVES PHYSICAL STABILITY
• The critical point is defined as the concentration of internal
phase above which the emulsifying agent can not produce a
stable emulsion of the desired type.
– Beyond the critical point, the globules become irregular in
shape. Closest packing of globules leads to coalescence.

44. FACTORS WHICH IMPROVES PHYSICAL STABILITY
• Phase inversion
– Phase inversion means a change of emulsion type from o/w
to w/o or vice versa
– Phase inversion is used to prepare stable and fine emulsion
– Phase inversion can be obtained by two ways
– i) Changing the chemical nature of emulsion

45. FACTORS WHICH IMPROVES PHYSICAL STABILITY
– Phase inversion
– An o/w type emulsion is prepared by using sodium stearate
– calcium chloride added to this
– oil soluble calcium stearate is formed
– ie. Oil phase becomes the continuous phase and w/o type
emulsion is produced
• eg:- white liniment

46. FACTORS WHICH IMPROVES PHYSICAL STABILITY
• Altering the phase volume ratio
– In this method o/w type emulsifier is mixed with oil and small
amount of water(the volume of water is small compared to the
oil)
– w/o type emulsion is formed
– As more water is added slowly , the inversion point is gradually
reached
– The emulsifier or water envelop the oil and form small globules
yield an o/w type emulsion.

47. • Phase volume ratio 50:50, upper limit is 74:26
• Phase volume ratio: 5% -newtonian flow
• Phase volume ratio :50% pseudoplastic
• Phase volume ratio:74% - plastic flow

48. THANK YOU