Formulation of Emulsions
At the end of this
lecture, student will be able to
• Explain the uses of emulsions
• Explain the formulation of emulsions
• Classify emulsifying agents
• Describe the properties of various emulsifying agents
• Explain the steps involved in the preparation of emulsions
• Outline the primary emulsion formulae
• Describe different methods of preparation of emulsions
Administration of Emulsions
1) Oral Emulsions
E.g 1: Liquid
Paraffin Oral Emulsion
E.g 2: Castor oil
E.g 3: Cod-Liver oil
2) Rectal Emulsions:
Enemas as O/W emulsions.
E.g 1: Starch Enema
3) Topical Emulsions: For external use –
emulsions may be O/W or W/O
E.g 1: Turpentine
E.g 2: Oily Calamine
emulsions: To be injected
E.g. Intravenous Fat emulsion
1. Choice of emulsion type
2. Choice of oil phase
3. Choice of emulsifying agent (emulgent)
1. Choice of emulsion
– Fats or oils for oral administration – O/W emulsions.
– I.V administration – O/W
– I.M injections – W/O emulsion – if a water soluble drug –
for depot therapy.
– Semisolid emulsions for external application – O/W or W/O
-Topical application of water soluble drugs- O/W
– Cleansing the skin of oil soluble dirt- W/O
2. Choice of oil
• Oil phase of an emulsion is the active agent – its conc.
in the product is predetermined.
• E.g. Liquid paraffin, castor oil, cod liver oil and
arachis oil – formulated as emulsions for oral administration.
• Cottonseed oil, soya bean oil and safflower oil – are used
in parenteral emulsions -their high calorific value.
•Turpentine oils, benzyl benzoate – external application
• Liquid paraffin, hard/soft paraffin – used alone or in
combination to control emulsion consistency
3. Choice of
emulsifying agent (emulgent)
• Emulsifying agents / Emulgents/ emulsifiers
• Prevent the coalescence of the globules of the dispersed
• They have both a hydrophilic and a lipophilic part in
their chemical structure.
• Adsorbed onto the oil/water interface
• Provide a protective barrier around the dispersed
• Reduce the interfacial tension between oil phase &
• Increases miscibility
• Forms a stable emulsion.
of action of Emulgent
It is a thick, creamy sauce often used as a condiment. It is
a stable emulsion of oil, egg yolks and either vinegar or lemon juice
To solubilize oil
Classification of Emulsifying Agents
• Best emulsifying agent
• For extemporaneous preparation of emulsion
• Good quality, stability & appearance – achieved with a
mortar & pestle
• Concentrated emulsion in the initial stage of preparation
is viscous & sticky.
• Due to vigorous shearing action of the pestle- oil is
easily reduced to fine globules)
• Emulsions are of low viscosity
• Thickening agents such as Tragacanth & sodium alginate
should be added.
• Palatable and stable over a wide pH range (2 – 1 0).
• Not used alone because of its high viscosity
• The emulsions are coarse
• Used as a stabilizer in acacia emulsions
• Used in proportion 1: 10(acacia).
3. Sodium alginate
• From brown seaweed
• High viscosity
• Used as an emulsion stabilizer in acacia emulsions
– Dried extract from certain seaweeds
– Emulsion stabilizer in acacia emulsion
– Soluble in boiling water
– High viscosity
– Poor emulsifying agent
-Preparation of enemas containing oils
– Obtained from the inner rind of citrus fruits or from
– Good O/W emulgent
– Degrades in alkaline pH
– Used as a stabilizer in cosmetic creams & lotions.
7. Chondrus (Irish
Moss or Carrageen)
– Dried seaweed
– Not suitable for small scale emulsification
– Time consuming
– Used in cod liver oil emulsions
– Masks the unpleasant odour & taste of the oil.
– 2.5% mucilage – emulsify an equal volume of fixed oil.
8. Wool fat (lanolin)
– Wax from the sebaceous glands of sheep
– Consists of fatty acid esters of cholesterol + other
sterols + normal fatty alcohols.
– Can absorb 50% of water
– When mixed with other fatty substances it can emulsify
several times its own weight of aqueous or hydroalcoholic liquids.
– The emulsions will be of W/O type
– From skin and bones of animals
– Used for the emulsification of liquid paraffin emulsions
at a concentration of 1 %
10. Egg yolk
– Emulsifying agent – lecithin & cholesterol
– Rarely used in industrial preparations
– Spoiled during transportation –
– Good preservation is necessary
11. Bees Wax
– Natural wax produced in the bee hive of honey bees
– Female worker bees have wax producing glands
– The wax is used to build honey comb cells
1. Methyl cellulose
– Low Viscosity grades are used
– Emulgents & emulsion stabilizers
– Suitable for emulsifying mineral & vegetable oils –
– Concentration of 2 %
– Medium viscosity grades are used
– Concentration of 0.5 -1 %
– Emulsion stabilizers.
– In aqueous solution
they ionize into a large anion and a small cation
– This anion has emulsifying ability
– They bear a negative charge
– There are of 5 types:
* Alkali metal & ammonium soaps
* Soaps of divalent & trivalent metals
* Amine soaps
* Alkyl sulphates
* Alkyl phosphates
Alkali Soap Emulsions
• Na+, K+ and NH4+soaps
• Stable above pH 10
• Sensitive to acids
• High concentration of electrolytes can salt out the soap
• Incompatible with polyvalent cations (Mg2+, Al3+, Zn2+)
• Cations cause phase reversal.
• Physiological action & unpleasant taste
• Unsuitable for internal emulsions
• High alkaline pH- avoid usage on broken skin.
• Emulgents only in O/W emulsions
E.g. Sodium stearate, Potassium stearate, Ammonium
Soaps of Divalent
& Trivalent Metals
• Calcium soaps (Calcium stearate) are preferred
• Used as W/O emulsifying agents
• Cannot be used internally
• Less alkaline & less sensitive to acid
• Incompatible with monovalent soaps
• Neutral (pH 7.5 to 8)
• Produce O/W emulsions
• Can be applied to broken skin
• Unsuitable for internal use.
• Esters of fatty alcohols and sulphuric acid
• SLS is preferred – O/W emulsions
• Low stability
• Can be used with fatty alcohols- to increase stability
• Used in combination with fatty alcohols
• Similar to alkyl sulphate
• The alcohols groups are phosphated instead of sulphated
• In aqueous solution they ionize into a large cation and a
• This cation has emulsifying ability
• They bear a positive charge
E.g. Quarternary ammonium compounds.
• Emulgent, disinfectant & preservative properties
• Combined with fatty alcohols for better emulsification
E.g. Benzalkonium chloride, Benzethonium chloride &
cetrimide (Cetyl trimethyl ammonium bromide).
3. Non- ionic:
• They do not ionize in aqueous solution
• The emulsion will be stable over a wide range of pH
• Not affected by addition of acids & electrolytes
E.g. Glycol & Glycerol esters (Glyceryl monostearate),
Sorbitan esters (Spans), Polysorbates (Tweens), Macrogols (Polyethylene
glycol), Poly vinyl alcohol.
Span 20 – lauric acid
Tween 20 – lauric acid
Span 40- palmitic acid
Tween 40- palmitic acid
Span 60 – stearic acid
Tween 60 – stearic acid
Span 80 – oleic acid
Tween 80 – oleic acid
• Finely divided solids
• Balanced hydrophobic & hydrophillic properties
• If the solid particles are preferentially wetted by the
oil- then W/O emulsions
• If wetted by water – O/W emulsions
E.g. Milk of
magnesia (10-20%) Magnesium oxide (5-10%) Magnesium aluminium silicate (1%)
– Used in ointments
– If Mol. weight is between
200-700 – viscous, light coloured, hygroscopic liquids.
– Mol. weight above 1000 – wax like solids.
– Used only in combination with other emulsifying agents
– Yellowish brown fatty substance
– occurs in plant and animal tissues
– Isolated from egg yolk, bile, human brain tissue, fish roe,
chicken and sheep brain, soy beans, eggs, cotton seed and sunflower.
The preparation of an emulsion involves two stages:
1. Preparation of the primary emulsion
2. Dilution of the primary emulsion.
Primary Emulsion Formula
Type of oil
Arachis oil, Castor oil, Cod liver oil, Almond oil
Cinnamon oil, Turpentine oil, Peppermint oil
Male fern extract
Preparation of Emulsions
1) Trituration method
a) Dry Gum or
Continental method: the emulsifying agent is mixed with the oil before the
addition of water.
b) Wet Gum or English
method: the emulsifying agent is added to the water to form mucilage and
then the oil is slowly incorporated to form the emulsion.
2) Bottle or Forbes method:
– Preparing emulsions containing volatile and other
– Both dry gum and wet gum methods can be employed
1. Routes of
administration of emulsions – Oral, Topical, Rectal, Parenteral
2. Formulation of
– Choice of emulsion type: O/W or W/O
– Choice of oil phase: Depending on whether internal/external/parenteral
– Choice of emulsifying agent (Emulgent)
agents: Are of 5 types
– Natural (Plant/ Animal source)
– Semi synthetic polysaccharides
4. Emulsifying agents
obtained from plant sources- Acacia, Tragacanth, Sodium Alginate, Agar,
Pectin, Chondrus, and Starch
5. Emulsifying agents
obtained from animal sources- Beeswax, Wool Fat, Gelatin and Egg Yolk
6. Semi- Synthetic
emulsifying agents: Cellulose derivatives
emulsifying agents: Anionic, Cationic and Non- ionic
8. Steps involved in
the preparation of emulsions- Primary emulsion preparation and Dilution of
9. Primary emulsion
formulae- For fixed, mineral, volatile oils and oleo resin
10. Methods of preparation
– Trituration method: Dry Gum and Wet Gum
– Bottle method: For volatile oils