Emulsions are thermodynamically unstable systems consisting of two immiscible liquid phases, one dispersed as globules in the other. In-process quality control tests are conducted to ensure emulsion stability and quality. Key tests include visual inspection, viscosity, particle size and distribution, phase volume ratio, and temperature fluctuations. Tests help identify and prevent instability issues like flocculation, creaming, coalescence, breaking, and phase inversion. Proper control of packaging materials and labels is also important for quality assurance.

1. INPROCESS QUALITY CONTROL OF
EMULSIONS
BY:
CH. SANDHYA
ASST. PROFESSOR
DEPT OF PHARM.
ANALYSIS

2. EMULSIONS
• Emulsion: Systems consisting of at least two immiscible
liquid phases, one of which is dispersed as small globules in
the other liquid phase.
• The globule diameter may range from 0.1 to100 μm.
• Emulsions are thermodynamically unstable systems.
Emulsions are also called as heterogeneous systems ,or
more precisely biphasic systems.

3. •Classification
1)Based on nature of dispersed phase
a)oil-in-water(o/w)
b)water-in-oil(w/o)
2)Based on the globule size
a) micro emulsions(0.01μm)
b) fine emulsions(0.25 to 25μm)

4. Instability of emulsions

5. Instability of emulsions
•Flocculation
• Neighbouring globules come closer to each other and
form colonies in the external phase.
•This is the initial stage that leads to instability
• The extent of flocculation of globules depends on
a)globule size distribution
b)charge on globule surface
c)viscosity of external medium

6. • Creaming
• Creaming is the concentration of globules at the top or
bottom of the emulsion.
• The floccules move either upward or downward leading to
creaming.
• It can be observed by a difference in colour shade of the
layers.
• Creaming is influenced by a)globule size b)viscosity of the
dispersion medium c)differences in the densities of
dispersed phase and dispersion medium

7. • Coalescence
•Coalescence is followed by creaming stage.
•In this process the emulsifier film around the globules is
destroyed to a certain extent.
• This step can be recognised by increased globule size
and reduced number of globules.
• Coalescence is observed due to a)insufficient amount of
the emulsifying agent b)altered partitioning of the
emulsifying agent c)incompatibilities between emulsifying
agents

8. •Breaking
•This is indicated by complete separation of oil and
aqueous phases.
•It is an irreversible process that is simple mixing fails to
resuspend the globules into an uniform emulsion.
• In breaking, the protective sheath around the globules is
completely destroyed.

9. • Phase inversion
• This involves the change of emulsion type from o/w to
w/o or vice versa.
•When we intend to prepare one type of emulsion say
o/w and if the final emulsion turns out to be w/o it can be
termed as a sign of instability

10. IPQC tests for emulsions
Appearance
Clarity testing
pH value
Viscosity
Rheology
Drug content uniformity
Particle size distribution
Densities of phases

11. Phase volume ratio
Charge of electrical double layer
Physical properties of interface
Temperature fluctuations
Quality control of water
Breaking or cracking
Compatibility of product with container-closure system

12. VISUAL INSPECTION :
With visual inspection, the ingredients and the final
products are carefully examined for purity and for
appearance .
Physical appearance of products for patient adherence and
compliance is critical so it should be: Good looking Elegant
in appearance .

13. VISCOSITY
•As the viscosity increases flocculation of globules will be
reduced .simultaneously the Brownian movement of
globules will also be hindered leading to creaming.
•Due to this antagonistic effect an optimum viscosity is
desirable for good stability.
• Viscosity can be measured by
• a)cup and bob viscometer
• b)cone and plate viscometer

14. PARTICLE SIZE
• As the globule size is reduced they tend to exhibit
Brownian movement.
• According to stokes law the diameter of the globule is
considered as a major factor in creaming of emulsion.
• The rate of creaming decreases four folds when the
globule diameter is halved.
• So it is necessary to choose the optimum globule size for
maximum stability.

15. PARTICLE SIZE DISTRIBUTION
• Globules of uniform size impart maximum stability.
In such emulsions globules pack loosely and globule to
globule contact is less.
•Globule distribution is effected by viscosity, phase volume
ratio, density of phases etc.
An optimum degree of size distribution range should be
choosen to achieve maximum physical stability.

16. GLOBULE SIZE DETERMINATION
•Microscopic examination of globule size distribution
analysis is an useful tool to evaluate the physical stability.
PHASE VOLUME RATIO
•In an emulsion the relative volume of water to oil is
expressed as phase volume ratio.
• In general most medicinal emulsions are prepared with a
volume ratio of 50:50.

17. •This proportion brings about loose packing of globules.
The upper limit 74% of oil can be incorporated in an
emulsion but this may lead to breaking of the emulsion.
This value is referred to as critical point of phase volume
ratio.
•Critical point is defined as the concentration of internal
phase above which the emulsifying agent cannot produce a
stable emulsion of the desired type.

18. PHASE INVERSION
•The emulsion is checked for phase inversion which means
a change of emulsion type from o/w to w/o or vice versa.
EXTENT OF PHASE SEPARATION
•The practical and commercial aspect of stability is the
study of phase separation.
•This is quick method and can be applied for poorly
formed and rapidly breaking emulsions.
•Separation of phases is visible after a definite period of
time, though the signs of instability begin quite early.

19. CHARGE OF ELECTRICAL DOUBLE LAYER
•When ionic type of emulsifier is employed, the electrical
double layer(interface between oil and water) possesses
charge.
•The repulsive forces, due to like charges on the surface of
the globules prevent the flocculation of globules

20. UNIFORMITY OF MASS
•Weigh individually the contents of 20 containers, empty it
completely, and determine the average mass.
•Not more than 2 of the individual masses deviate by more
than 10 per cent from the average mass and none deviates
by more than 20 per cent.

21. PHYSICAL PROPERTIES OF INTERFACE
• The interfacial film of the emulsifier is responsible for
enhancing the stability of the product.
• The film should be elastic enough to form rapidly as soon
as droplets are produced. This behaviour facilitates the
production of emulsion.
• Similarly on moderate shaking the emulsion should be
reconstituted.
• After manufacture the film should be tough so that
coalescence of globules can be prevented.

22. •So suitable emulsifying agents such as surfactants should
be selected to achieve the above film properties at the
interface.
DENSITIES OF PHASES
•By adjusting the density of the phases to the same value
we can increase the stability of emulsion.
•Oil phase density can be enhanced by adding brominated
oil when the oil is an external phase.

23. DILUTION TEST:
•The emulsion is diluted with water. In case the emulsion
remains stable after its dilution, it is o/w emulsion.
•The w/o emulsion breaks on its dilution with water but
remains stable when diluted with oil.
DYE TEST:
•The scarlet red dye is mixed with the emulsion. Place a
drop of the emulsion on a microscopic slide, Cover it with a
cover- slip, and examine it under a microscope. If the
disperse globules appear red and the ‘ground ’ colourless,
the emulsion is o/w type.

24. •The reverse condition occurs in w/o type emulsion i.e.,
the disperse globules appear colourless in the red ‘ground’.
CRACKING TEST:
•By addition of emulsifying agent of opposite type : Soaps
of monovalent metals produce o/w type emulsions
whereas soaps of divalent metals produce w/o type
emulsions.
• But the addition of monovalent soap to a divalent soap
emulsion or a divalent soap to a monovalent soap
emulsion leads to cracking of emulsion.

25. •By decomposition or precipitation of emulsifying agents:
When an acid is added to an alkali soap emulsion
(turpentine liniment), it causes the decomposition of an
emulsifying agent and thus leads to cracking of an
emulsion.
•Similarly, when sodium chloride is added to sodium or
potassium soap emulsion, it leads to the precipitation of
emulsifying agents and thus cracking of emulsion take
place.

26. TEMPERATURE FLUCTUATIONS
•Elevated temperatures alter the partition characteristics of
the emulsifiers and preservatives results in instability.
•Temperature also enhances the chemical degradation of
drugs and other ingredients.
•At lower temperature the aqueous phase may contain ice
crystals which rupture the interfacial film and break the
emulsion.
• So care should be taken to prevent temperature
fluctuations during manufacture and storage.

27. COMPLETION STAGE
At the completion of manufacturing process as well as in-
process stages, actual yields are checked against theoretic
value and the representative sample are withdrawn for
laboratory testing by the control inspector according to the
predetermined sampling plan.
RECORD AND REPORT
The batch production records and other needed
documents are then delivered to the quality control office
together with the withdrawn samples of the products.

28. PACKAGING MATERIAL CONTROL
• Packaging material should not interact physically or
chemically with the finished product to alter the strength,
quality or purity beyond specified requirements.
• The following features are to be considered in developing
container specifications:
• Properties of container tightness
•Moisture and vapour tightness regardless of container
construction
•Compatibility between container and product

29. •Toxicity and chemical/physical characteristics of materials
needed in container construction.
•Physical or chemical changes of container upon
prolonged contact with product
LABELS CONTROL
•Production control issues a packaging form that carries
• The name of the product, Item number, Lot number,
Number of labels, Inserts, Packaging material to be used,
Operation to be performed, Quantity to be packaged.

30. • A copy of this is sent to the supervisor of label control,
who in turn counts out the required number of labels.
•Conclusion
•IPQC tests are carried out during the manufacturing to
ensure stable, safe and quality product.

31. • References
• Lachman L,Lieberman H,The Theory andPractice of
Industrial pharmacy;3rdedition,page number-810 to 835.
• C.V.S.Subrahmanyam, Text book of Physical
Pharmaceutics,page number-195 to 203,366to 423.
• Encyclopedia volume-6 page number 3105-3107.