This document provides information on emulsions and suspensions. It defines emulsions as dispersions with one liquid dispersed in another immiscible liquid, stabilized by an emulsifying agent. Emulsions are classified based on the dispersed and continuous phases. Suspensions are heterogeneous mixtures where particles settle out over time. Key factors that affect sedimentation rates in suspensions are described by Stokes' equation. Common emulsifying agents and suspending agents used in pharmaceutical formulations are also outlined.

1. EMULSION AND
SUSPENSION
PRESENTED BY
SAKSHI SINGH
MODERN
PHARMACEUTICS
(MPH103

2. EMULSIONS

3. INTRODUCTION
 An 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.
 The stability against drop coalescence is provided by the presence of a small
amount of a third component, so-called emulsifier, which is in general a
surfactent-agent or surfactant, that adsorbs at the drop interface and produces
some inter drop repulsion according to a variety of static and dynamic phenomena

4. Classification of emulsions :
 Based on dispersed phase
• Oil in Water (O/W): Oil droplets dispersed in water
• Water in Oil (W/O): Water droplets dispersed in oil
 Based on size of liquid droplets
• 0.2 – 50 mm Macroemulsions (Kinetically Stable)
• 0.01 – 0.2 mm Microemulsions (Thermodynamically Stable)

5. Theories of
Emulsification:
 Surface Tension Theory
 Oriented-Wedge Theory
 Interfacial film theory
 Charge repulsion theory
 Steric repulsion theory

6. SURFACE TENSION THEORY
 According to the surface tension theory of emulsification, the emulsifying agents
cause a reduction in the interfacial tension of the two immiscible liquids, reducing
the repellent force between the liquids and withdrawing the attraction of liquids
for their own molecules. In this way, the surfactants convert large globules into
small ones and avoid small globules from coalescing into large ones.
 In this way, the surfactants convert large globules into small ones and avoid
small globules from coalescing into large ones.

7. ORIENTED-WEDGE THEORY
 This theory deals with formation of monomolecular layers of emulsifying agent
curved around a droplet of the internal phase of the emulsion. Example
 In a system containing two immiscible liquids, emulsifying agents would be
preferentially soluble in one of the phases and would be embeded in that phase.
A. Emulsifier molecules oriented at interface

8. INTERFACIAL FILM THEORY
 When two immiscible liquids come in contact, the force causing each liquid to
resist breakage is known as interfacial tension. When a high interfacial tension
existed between two liquids emulsification is difficult, and if the tension could be
reduced emulsification facilitated.
 The explanation that in oil in water dispersion, the interfacial tension is so great
that when two globules of dispersed phase approach each other it withdraws the
liquid from between them, with the result they coalesce. When the interfacial
tension is greatly reduced by the addition of emulsifier the globules remain
separate.

9. CHARGE REPULSION THEORY
 This theory of emulsions says that the fine globules of dispersed phase are
separated due to the repulsive forces developed as a result of the nature of
emulsifying agent (anionic or cationic) or by adsorbing ions from the dispersion
medium.
 Charge develops on the surface of oil globules (o/w) is great enough to cause
repulsion between droplets.
 The electrical barrier to prevent coalescence of the oil droplets and allow the oil
phase to remain in droplet form, uniformly dispersed in continuous water phase.

10. STERIC REPULSION THEORY
 This theory says that the repulsion develops between the water droplets due to the
long hydrocarbon chains of emulsifying agent which has been adsorbed on their
surface.
 This repulsion is called d steric repulsion, preventing the contact or coalescence
of water droplets.
 theory can explain the process of emulsification only in w/o type of emulsion.

11. EMULSIFYING
AGENT
 An emulsifying agent (emulsifier) is a surface-active
ingredient which adsorbs at the newly formed oil–
water interface during emulsion preparation, and it
protects the newly formed droplets against immediate
recoalescence.
 Pharmaceutically acceptable emulsifiers must also :
• 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 .

12. EXAMPLES OF EMULSIFYING AGENTS
1) Carbohydrate Materials: - Acacia, Tragacanth, Agar, Pectin. o/w emulsion. „
2) Protein Substances: -Gelatin, Egg yolk, Caesin o/w emulsion.
3) High Molecular Weight Alcohols: - Stearyl Alcohol, Cetyl Alcohol, Glyceryl Mono
stearate o/w emulsion, cholesterol w/o emulsion.

13. MECHANISM OF EMULSION
 •The increase in the energy of an emulsion compared to the nonemulsified
components is equal to ∆W. This amount of energy can be considered as a
measure of the thermodynamic instability of an emulsion
 DW = g D A
 ∆W is the free energy of the interface and corresponds to the reversible work
brought permanently into the system during the emulsification process . This
makes an emulsion very prone to coalescence processes which lead to a decrease
in ∆A and subsequently in ∆W. The conclusion is straightforward that ultimate
stability against coalescence processes is only achieved if s approaches zero

14. TEST FOR IDENTIFICATION
 Dilution test: emulsion can be diluted only with external phase
 Dye test: water or oil soluble dyes
 CoCl 2/filter paper test: filter paper impregnated with CoCl 2 and dried (blue)
changes to pink when o/w emulsion is added
 Fluorescence: some oils fluoresce under UV light
 Conductivity: for ionic o/w emulsions (o/w emulsions conduct electric current)

15. APPLICATION OF EMULSION
 In the metallurgical processes, the concentration of ore by forth floatation process
is based upon the treatment of the powdered ore with oil emulsion. The valuable
particles of the ore form foam which comes to the surface and is skimmed off.
 Asphalt emulsified in water is used for building roads without the necessity of
melting the asphalt.
 Milk which is an important constituent of our diet is en emulsion of liquid fats in
water.
 Several oily drugs are prepared in the form of emulsions.
 The cleansing action of ordinary soap for washing clothes, crockery etc. is based
upon the formation of oil-in-water emulsion.

16. SUSPENSIONS

17. INTRODUCTION
 A suspension is a heterogeneous mixture in which some of the particles settle out of the
mixture upon standing. ... The particles in a suspension are far larger than those of a solution and
thus gravity is able to pull them down out of the dispersion medium (water).
PROPERTIES:-
 Heterogenous biphasic dosage form
 solid is dispersed in liquid medium. Dispersed phase, dispersion medium
 -Rapid settling
 Easily redispersible ,pourable
 if parenteral—flow through syringe needle
 -if external---spread easily
 -Pleasing in colour , odour, appearance.

18. CLASSIFICATION
OF SUSPENSIONS
 Based On General Classes
• Oral suspension
• Externally applied suspension
• Parenteral suspension
 Based On Proportion Of Solid Particle
• s Dilute suspension (2 to10%w/v solid)
• Concentrated suspension (50%w/v solid)
o Based On Electrokinetic Nature Of Solid Particles
• Flocculated suspension
• Deflocculated suspension
o Based On Size Of Solid Particles
• Colloidal suspension (< 1 micron)
• Coarse suspension (>1 micron) Nano suspension (10
ng)

19. THEORY OF SUSPENSION
 Sedimentation Behaviour
Sedimentation means settling of particle or
floccules occur under gravitational force in
liquid dosage form.
 Theory of Sedimentation
 The factors affecting the rate of
sedimentation of a particle are described in
Stoke’s equation

20. STOKES EQUATION
 Th e basic consequences of the stokes equation are that the rate of fall of a suspended particle in a
vehicle of a given density is greater for larger particles than it is for smaller particles. Also the
greater the difference in density between the particles and the vehicle, the greater will be the rate
of sedimentation. Increasing the viscosity of the dispersion medium will reduce the rate o
sedimentation. Thus decrease in the rate of sedimentation of particles in a suspension may be
achieved by reducing the size of the dispersed particles and by increasing the density and viscosity
of the dispersion/continuous phase.

21. SUSPENDING AGENTS
 Suspending agents are substances that are used to keep finely divided insoluble materials suspended
in a liquid media by preventing there agglomeration (coming together) and by imparting viscosity to
the dispersion media so that the particles settle more slowly
 NATURALAGENTS This class consists of those from.
a) . Animal source eg Gelatine
b) .Plant source eg. Accacia, Tragacanth, Starch, sea weed (Alginates)'
c) . mineral sources.eg Bentonite, Kaoline 2.
 SEMI-SYNTHETIC AGENTS
a) These consist of substituted cellulos (minerals) eg. Hydroxyethylcellulose , Sodium
Carboxymethylcellulose , methylcellulose, Microcrystalline cellulose

22. Flocculation is a condition which occurs as a result of the lowering of electrical forces
of repulsion in a dispersed system , so that the force of attraction predominate. Systems
under this condition reduced repulsive forces the dispersed particles to approach each
other more closely and form aggregates known as flocs
 In flocculated suspension, formed flocs (loose aggregates) will cause increase in
sedimentation rate due to increase in size of sedimenting particles. Hence, flocculated
suspensions sediment more rapidly.
The Sedimentation Behavior of Flocculated and
Deflocculated Suspensions:
FLOCCULATED
SUSPENSION

23. A deflocculated suspension is one in which the electrical repulsive forces between particles
exceeds the attractive forces, the particles are kept apart as individuals affected only by the
suspending vehicle. Even when brought together by random motion, they resist collision due to the
high surface tension.
 In deflocculated suspension, individual particles are settling, so rate of sedimentation is slow
which prevents entrapping of liquid medium which makes it difficult to re-disperse by agitation.
This phenomenon also called ‘cracking’ or‘claying’.
 In deflocculated suspension,smaller particles settle slowly and therefore remaining supernatant
liquid so supernatant appears cloudy and has a pleasing granular appearance whereby in flocculated
suspension, even the smallest particles are involved in flocs, so the supernatant does not appear
cloudy.
DEFLOCCULATED SUSPENSION

25. APPLICATION OF SUSPENSION
 Suspension can be formulated for parentral application in order to control rate of drug absorption,
E.g. penicillin procaine
 Vaccines as a immunizing agent are often formulated as suspension.E.g. Cholera vaccine
 X-ray contrast agent are also formulated as suspension. E.g. Barium sulphate for examination of
alimentary tract
 If the drug is unstable when in contact with the vehicle, suspensions should be prepared
immediately prior to handing out to the patient in order to reduce the amount time that the drug
particles are in contact with the dispersion medium. Eg Amoxicilin suspension
 Lotions containing insoluble solids are formulated to leave a thin coating of medicament on the
skin. As the vehicle evaporates, it gives a cooling effect and leaves the solid behind.eg calamine
lotion and sulphur lotion compound.