This document defines and describes emulsions. An emulsion is a biphasic liquid preparation containing two immiscible liquids, one dispersed as minute globules into the other. The liquid dispersed is called the dispersed phase while the liquid it is dispersed in is the continuous phase. Emulsions are stabilized by emulsifying agents which form films around the globules. Emulsions can be classified based on globule size, dispersed and continuous phases, and the emulsifying agent used. Identification tests include dilution, dye, conductivity, and fluorescence tests to determine the emulsion type. Emulsions offer advantages like masking unpleasant tastes, protecting drugs, and facilitating absorption of oils.

1. EMULSION
Ronald Peter
Assistant Professor
Dept. of Pharmaceutics

2. Definition
 Emulsion is a biphasic liquid preparation containing two immiscible liquids, one of
which is dispersed as minute globules into the other.
The liquid converted to minute globules – dispersed phase
The liquid in which globules are dispersed – continuous phase
 Normally – 2 immiscible liquids alone – cannot exit as dispersed form – for long
time.
 So an emulsifying agent – added to the system
 It forms a film around the globules – reduces IT – helps to scatter uniformly – stable
emulsion formed.
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3. 3 Lisie College of Pharmacy, Kochi
Formation of o/w or w/o
type emulsion
Orientation of surfactant
Natural emulsion

4. Advantages
• Medicines having unpleasant taste and odour – can be made more palatable
• Protection for drugs – prone to oxidation and hydrolysis
• Novel preparations – creams, lotions, foam aerosols – formulated as emulsions
• Sterile IV emulsions can be prepared and administered
• Emulsion improves absorption of oils – when taken orally
• Radio opaque emulsions can be prepared – used as diagnostic agents
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5. Types
I. Based on globule size
Usual globule size of emulsion – 0.25µm to 25µm
• Coarse emulsion – large globules
• Fine emulsion – globule size of 5µm
• Micro emulsion – small as 10nm
(Emulsions are milky / white due to reflection and refraction at many interfaces
and almost transparent if the RI are almost same for two phases)
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6. II. Based on dispersed phase / continuous phase
Oil in water type (o/w)
Water in oil type (w/o)
Multiple emulsion
w/o/w type
o/w/o type
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7. o/w type emulsion
Dispersed phase?
Oil phase
Continuous phase?
Aqueous phase
w/o type emulsion
Dispersed phase?
Aqueous phase
Continuous phase?
Oil phase
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Preferred for Internal use
Emulsifying agents used;
Gum acacia, tragacanth, methyl cellulose, saponins
and soaps formed from monovalent bases like Na+, K+
and NH4
+
Preferred for External use
Emulsifying agents used;
Wool fat, resin, beeswax
and soaps formed from divalent bases like Ca++, Mg++
and Zn++

8. Identification test for emulsion
 Dilution test
 Dye test
 Conductivity test
 Fluorescence test
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9. 9 Lisie College of Pharmacy, Kochi
o/w type
Stable
Dilution test

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w/o type
Phase inversion / Breaking
(Unstable)

11. In short
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Diluent liquid Water Oil
Stability Stable Unstable Stable Unstable
Continuous
phase
Water Oil Oil Water
Dispersed
phase
Oil Water Water Oil
Type o/w w/o w/o o/w

12. Dye test
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Scarlet red (oil
soluble dye)
o/w type
w/o type
Oil phase
(Appears red in colour)
Aqueous phase
(Appears colourless)
Oil phase
(Appears red in colour)
Aqueous phase
(Appears colourless)
Observed
Under
microscope

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Methyl Blue
(aqueous soluble
dye)
o/w type
w/o type
Oil phase
(Appears colourless)
Aqueous phase
(Appears blue in colour)
Oil phase
(Appears colourless)
Aqueous phase
(Appears blue in colour)
Observed
Under
microscope

14. Conductivity test
Basic concept; Water – good conductor & Oil – bad conductor of electricity
 Dip a pair of electrodes in, emulsion to be identified and connected to a low
voltage bulb. Then pass electric current through it
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+
-
o/w type emulsion
Bulb glows

15. If the bulb glows – emulsion is o/w type – because water is the continuous phase
If the bulb doesn't glow – emulsion is w/o type – because oil is the continuous phase
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+
-
w/o type emulsion
Bulb doesn’t glows

16. Fluorescence test
Basic principle; certain fixed oils (olive)
produce fluorescence
in presence of UV light
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Certain fixed oil
o/w type
w/o type
Oil phase
(Florescence)
Aqueous phase
(No Florescence)
Oil phase
(Florescence)
Aqueous phase
(No Florescence)
Microscopic
observation
Under UV

17. Classification of Emulsions
Classification of emulsion is done on two basic aspects;
I. Based on the type of emulsifying agent used in preparation
a. Emulsions containing natural gum (gum acacia, tragacanth, Irish moss)
b. Emulsions containing gum substitute (cellulose and its derivatives)
c. Emulsions containing various soaps (divalent and bivalent soaps)
d. Emulsions containing saponins
e. Emulsions containing starch
f. Emulsions containing natural waxes (wool fat, beeswax)
g. Emulsions containing synthetic waxes (cetomacrogol wax)
h. Emulsions containing other emulsifying agents (pectin, egg yolk, gelatin)
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18. II. Based on their mode of administration
a. Emulsions for oral administration
usually o/w type emulsion. Used to administer oils with medicinal value
b. Emulsions for external use
either o/w or w/o type emulsions. But preferably – o/w type emulsions
c. Emulsions for parentral use
used to administer fat soluble vitamins (A,D,E and soluble sex hormones)
their absorption in this form is very rapid
d. Emulsions for rectal use
used in form of enema. Starch mucilage is commonly used.
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19. To be continued.................
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