emulsion process

1. Manufacturing and process
conditions for emulsion
Presented by -
Amartya Nandi
M.Pharm (Pharmaceutics)
2023001515

2. Introduction
 When two immiscible liquids are mechanically agitated, it form droplets, the lifetime
of the droplets is materially increased by added emulsifier to the immiscible liquids.
Usually, only one phase persists in droplet form for a the internal (disperse or
discontinuous) phase and is surrounded by an external (continuous) phase.
 Spherical droplets as the internal phase can occupy no more than approximately 74%
of the total volume of an emulsion.
 The particle size of the disperse phase emulsion ranges from 0.25 to 10 µm.
 If the oil droplets are dispersed in a continuous aqueous phase, the emulsion is termed
oil-in-water (o/w); if the oil is the Emulsions continuous phase, the emulsion is of the
water-in-oil type (w/o).

3. Manufacturing of Emulsion
• Emulsions are prepared by adding one phase to the other, with one or both phases
containing emulsifier, and applying shear. The application of energy in the form of
heat, mechanical agitation, ultrasonic vibration or electricity is required to produce
the internal phase into small droplets.

4. • Condensation method-
Vaporization is an effective way of breaking almost all
the bonds between the molecules of a liquid.
Prepare emulsions by passing the vapour of a liquid into
an external phase that contains suitable emulsifying
agents. This process of emulsification, called the
condensation method.
It is as relatively slow, having a relatively low vapour
pressure and is therefore primarily of
theoretical importance.
Changes in temperature alter the distribution coefficients
of emulsifiers between the two phases and cause
emulsifier migration.
The distribution of the emulsifier as a function of
temperature cannot be correlated directly with either
emulsion formation or stability, since changes in surface
tension and viscosity occur simultaneously

5. Phase Inversion Method
This type of inversion can occur during the formation of
emulsions, since they are generally prepared at relatively high
temperatures and are then allowed to cool to room
temperature. It is quite stable .
The PIT is generally considered to be the temperature at
which the hydrophilic and lipophilic properties of the
emulsifier are in balance and is therefore also called the
HLB temperature.
w/o emulsions of benzene in convert to o/w emulsions upon
heating and reform w/o emulsions upon cooling. The
temperature at which inversion occurs depends on emulsifier
concentration.

6. Low energy emulsification
• This process of emulsion prepare in low-energy emulsification, only a portion of the external
phase, is heated.
• After emulsification of the heated portions, the remain of the external phase is added concentrate,
or the preformed concentrate is blended into the continuous phase.
• In those emulsions in which a phase inversion temperature exists, the emulsion concentrate is
preferably prepared above the PIT, which results in emulsions having extremely small droplet
size.
• It is important to effect in situ neutralization of acidic emulsifying components during
the emulsion step. It is possible to produce more emulsion with smaller and more uniform particle
size .

8. Spontaneous emulsification
 Spontaneous emulsification occurs when an emulsion
is formed without any external agitation
 The former are blends of the internal phase with
emulsifiers, which "bloom" when they are added to the
external phase.
 when a drop of oil is placed on an aqueous solution of
an emulsifier, in which case the interface becomes
extremely unstable and results in the formation
of fine droplets.
 Microemulsions commonly form spontaneously, but
not all spontaneous emulsions are transparent.
Emulsifiable concentrates are typical examples.

9. Mechanical equipment for emulsification
• Used for breaking up the internal phase into droplets depend on force and
require some sort of agitation. When a liquid jet of one liquid is
introduced under pressure into a second liquid, the initially cylindric jet
stream is broken up into droplets. Various types of equipment are
available to affect droplet break-up and emulsification either in the
laboratory or in production. Such equipment can be divided into four
broad categories -

10. Homogenizer
 In a homogenizer, the dispersion of two liquids is achieved by forcing
their mixture through a small inlet orifice at high pressures.
 It is useful for handling either liquids or pastes, since the rate of
throughput is little affected by viscosity.
 Homogenization raises the temperature of the emulsion, and
subsequent cooling may be required. Uses in monodisperse emulsion
of low particle size is required.
Mechanical stirrers
 An emulsion may be stirred by impellers mounted on shafts, which
are placed directly into the system to be emulsified.
 Simple top-entering propeller mixers are adequate for routine
development work in the laboratory and for production purposes, if
the viscosity of the emulsion is low.
 If more vigorous agitation is required , or if the preparation has
moderate viscosity, turbine type mixers are employed both in the
laboratory and in production.

11. Ultrasonifier
 The use of ultrasonic energy to produce pharmaceutical emulsions
many laboratory-size models are available.
 These transduced piezoelectric devices
 They are useful for the laboratory preparation of fluid emulsions of
moderate viscosity and extremely low particle size.
Colloid mills
 It is operate on the principle of high shear, which is generated
between the rotor and the stator of the mill
 It are used primarily for the comminution of solids and for the
dispersion of suspensions containing poorly-wetted solids but are
also useful for the preparation of relatively viscous emulsions.

12. Process Condition
Preparing an oil phase all the oil-soluble ingredients and to heat it at about 5 to 10°C
above the melting point and the aqueous phase also heated to the same temperature, and
mixed.
 In the preparation of anionic or cationic o/w emulsions, it is customary to add the oil
phase to the water phase, although sometimes it prefer the inversion technique.
 In the case of non-ionic emulsions, which exhibit a PIT, if soap is used as the emulsifier,
it is usually prepared in situ by combining the alkali with the water phase and
the fatty acid with the oil phase.

13.  In the preparation of w/o emulsions, it is almost always necessary to add the water phase
slowly to the oil/emulsifier blend . volatile flavors or perfumes are preferably added at the
lowest temperature at which incorporation into the emulsion is possible (usually 55 to
45°C).
 If a gum is employed, it should be completely hydrated or dissolved in the aqueous phase
before the emulsification step. If a heat- sensitive gum is used, it may be necessary to
incorporate the gum solution after the emulsion has been formed.
parenteral administration can be prepared with only a limited number of emulsifiers .
Those designed for intravenous injection, be homogenized until a satisfactory particle size
is achieved.
 Whenever an emulsion is formed at elevated temperatures, the loss of water due to
evaporation must be made up. This is done best by adjusting to "final weight" with water
when the emulsion reaches about 35°C.

14. References
Lachman / Liberman’s , The Theory and Practice of Industrial Pharmacy.
Guha, I.F., Anand, S. & Varanasi, K.K. Creating nanoscale emulsions using condensation.
Nat Commun 8, 1371 (2017). https://doi.org/10.1038/s41467-017-01420-8
Bibette, J., Leal Calderon, F. & Poulin, P. Emulsions: Basic principles. Rep. Prog. Phys.
62, 969–1033 (1999).