Disperse systems

1. Disperse Systems
Dr. Basavaraj K. NanjwadeM. Pharm., Ph. D
Department of Pharmaceutics
Faculty of Pharmacy
Omer Al-Mukhtar University
Tobruk, Libya.
E-mail: nanjwadebk@gmail.com
06/05/2015 1
Faculty of Pharmacy, Omer Al-Mukhtar University,
Tobruk, Libya.

2. CONTENTS
1. Introduction and classification.
2. Interfacial phenomenon.
3. Wetting phenomenon.
4. Adsorption.
5. Surface active agents.
6. Micellar solubilzation.
7. Solubitization in pharmacy.
8. Coarse of dispersion systems,
(a) Emulsions (definition, theory, determination of type, emulsifying agents, stability).
(b) Colloids (definition, types, properties, stability, applications)
(c) Suspension (definition, types, properties, stability, applications)
Including: classifications, desirable quality of acceptable suspension,
Interfacial properties of suspended particles, settling in suspension,
Formulation, flocculating agents, preparation of suspension.
06/05/2015 2
Faculty of Pharmacy, Omer Al-Mukhtar University,
Tobruk, Libya.

3. 1. Introduction
• Dispersed systems consist of particulate matter,
known as the dispersed phase, distributed throughout
a continuous or dispersion medium.
• The dispersed material may range in size from
particles of atomic and molecular dimensions to
particles whose size is measured in millimeters.
06/05/2015
Faculty of Pharmacy, Omer Al-Mukhtar
University, Tobruk, Libya.
3

4. Classification of dispersed
systems on the basis of particle
size
06/05/2015
Faculty of Pharmacy, Omer Al-Mukhtar University,
Tobruk, Libya.
4
Class Range of particle
size*
Characteristics of
size
Examples
Molecular dispersion Less than 1 nm Invisible in electron
microscope
Undergo rapid
diffusion
Oxygen molecules,
ordinary ions,
glucose
Colloidal dispersion From 1 nm to 0.5
µm
Visible in electron
microscope
Diffuse very slowly
Colloidal silver
solutions, cheese,
butter, jelly, milk,
shaving cream etc.
Coarse dispersion Greater than 0.5 µm Visible under
microscope
Do not diffuse
Grains of sand, most
pharmaceutical
emulsions and
suspensions, red
blood cells
*1 nm (nanometer)=10-9
; 1 µm (micrometer)=10-6
.

5. 2. Interfacial phenomenon
• The boundary between two phases is generally
described as an interface.
• When one of the phases is a gas or a vapour, the term
surface is frequently applied.
• In pharmacy, interfacial phenomena play an
important role in the processing of a wide variety of
formulations.
• The subsequent behavior of these formulations in
vivo is often governed by an interfacial process.
06/05/2015
Faculty of Pharmacy, Omer Al-Mukhtar University,
Tobruk, Libya.
5

6. 3. Wetting phenomenon
• Air may be trapped in the particles of poorly wetted
solids which causes them to float to the surface of the
preparation and prevents them from being readily
dispersed throughout the vehicle.
• Wetting of the particles can be encouraged by
reducing the interfacial tension between the solid and
the vehicle, so that adsorbed air is displaced from
solid surfaces by liquid.
• Suitable wetting agents have this effect, but decrease
interparticular forces thereby affecting flocculation.
06/05/2015
Faculty of Pharmacy, Omer Al-Mukhtar
University, Tobruk, Libya.
6

7. 4. Adsorption
• Adsorption, the binding of molecules or particles to a
surface, must be distinguished from absorption, the
filling of pores in a solid.
• The binding to the surface is usually weak and
reversible.
• Just about anything including the fluid that dissolves
or suspends the material of interest is bound, but
compounds with color and those that have taste or
odor tend to bind strongly.
06/05/2015
Faculty of Pharmacy, Omer Al-Mukhtar University,
Tobruk, Libya.
7

8. 5. Surface active agents
• Many compounds have structure that contain two
separate regions, a hydrophilic region (water-liking)
which confers on the compound a solubility in water,
and a hydrophobic region (water-hating) which
render the material soluble in hydrocarbon solvents.
• It is energetically favourable for these materials,
when dissolved, to adsorb at interfaces, orientating
themselves in such a manner that the regions are
associated with the appropriate solvent.
• Such materials are termed surface active agents (or
surfactants).
06/05/2015
Faculty of Pharmacy, Omer Al-Mukhtar University,
Tobruk, Libya.
8

9. 6. Micellar solubilzation
• Micellar solubilization can also increase the solubility
of drugs in the gastrointestinal tract.
• The ability of bile salts to solubilize drugs depends
mainly on the lipophilicity of the drug.
06/05/2015
Faculty of Pharmacy, Omer Al-Mukhtar
University, Tobruk, Libya.
9

10. 7. Solubitization in
pharmacy
• A wide range of insoluble drugs have been
formulated using the principle of solubilization, some
of which will be considered here.
• Solubilization has been shown to have a modifying
effect on the rate of hydrolysis of drugs.
• Non-polar compounds solubilized deep in the
hydrocarbon core of a micelle are likely to be better
protected against attack by hydrolysing species than
are more polar compounds located closer to the
micellar surcafe.
06/05/2015
Faculty of Pharmacy, Omer Al-Mukhtar University,
Tobruk, Libya.
10

11. 8. Coarse of dispersion
systems
A. Emulsion
B. Colloids
C. Suspension
06/05/2015
Faculty of Pharmacy, Omer Al-Mukhtar
University, Tobruk, Libya.
11

12. A. Emulsions
• An emulsion is a biphasic liquid preparation containing two
immiscible liquids, one of which is dispersed as minute globules
into the other.
• The liquid which is converted into minute globules is called the
‘dispersed phase’ and the liquid in which the globules are
dispersed is called the ‘continuous phase’.
• Normally, two immiscible liquids cannot be dispersed for a long
period.
• So, an emulsifying agent is added to the system.
• It forms a film around the globules in order to scatter them
indefinitely in the continuous phase, so that a stable emulsion is
formed.
• The globule size in emulsion varies from 0.25 to 25 µm.
06/05/2015
Faculty of Pharmacy, Omer Al-Mukhtar University,
Tobruk, Libya.
12

13. Theory of Emulsification
• There is no universal theory of emulsification,
because emulsions can be prepared using several
different types of emulsifying agent, each of which
depends for its action on a different principle to
achieve a stable product.
• For a theory to be meaningful, it should be capable of
explaining (1) the stability of the product and (2) the
type of emulsion formed.
• Let us consider what happens when two immiscible
liquids are agitated together so that one of the liquids
is dispersed as small droplets in the other.
06/05/2015
Faculty of Pharmacy, Omer Al-Mukhtar University,
Tobruk, Libya.
13

14. Types of emulsion
• Generally, the two liquids that form an emulsion are
an oil and water.
– Two types of emulsion
1.Oil in water emulsion (O/W emulsion): oil is in
the dispersed phase and water in dispersion
medium or continuous phase.
2.Water in oil emulsion (W/O emulsion): water is
in the dispersed phase and oil in dispersion
medium or continuous phase.
06/05/2015 14
Faculty of Pharmacy, Omer Al-Mukhtar University,
Tobruk, Libya.

15. Determination of type of
emulsion
• The followings tests are done to distinguish between
o/w and w/o emulsions.
1. Dilution test
2. Dye test
3. Conductivity test
4. Fluorescence test
06/05/2015
Faculty of Pharmacy, Omer Al-Mukhtar
University, Tobruk, Libya.
15

16. 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.
06/05/2015
Faculty of Pharmacy, Omer Al-Mukhtar University,
Tobruk, Libya.
16

17. 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.
• The reverse condition occurs in w/o type emulsion
i.e., the disperse globules appear colourless in the red
‘ground’.
06/05/2015
Faculty of Pharmacy, Omer Al-Mukhtar
University, Tobruk, Libya.
17

18. Conductivity test
• Water is a good conductor of electricity, whereas oil
is non-conductor of electricity.
• The conductivity test can be performed by dipping a
pair of electrodes connected through a low voltage
bulb in the emulsion.
• If the bulb glows on passing the electric current, the
emulsion is o/w type, because water is in the
continuous phase.
• In case the bulb does not glow, the emulsion is w/o
type, because oil is in the continuous phase.
06/05/2015
Faculty of Pharmacy, Omer Al-Mukhtar University,
Tobruk, Libya.
18

19. Fluorescence test
• Certain fixed oils possess the physical property of
fluorescing in the presence of ultraviolet radiation.
• On microscopic observation of emulsion under
ultraviolet radiation, the whole field fluorescence
indicates that oil is present in continuous phase (w/o
type emulsion) and droplets fluorescence indicates
that oil is present in dispense phase (o/w type
emulsion).
06/05/2015
Faculty of Pharmacy, Omer Al-Mukhtar
University, Tobruk, Libya.
19

20. Emulsifying agents
• The emulsifying agents reduce the interfacial tension
between two phases i.e., oily phase and aqueous
phase and thus make them miscible with each other
and form a stable emulsion.
• Emulsifying agents are also known as emulgents or
emulsifiers.
E.g. Acacia, Glyceryl monosterate, Tragacanth, etc.
06/05/2015
Faculty of Pharmacy, Omer Al-Mukhtar University,
Tobruk, Libya.
20

21. 06/05/2015 21
Faculty of Pharmacy, Omer Al-Mukhtar University,
Tobruk, Libya.
Emulsifying agents

22. Stability
• An emulsion is said to be stable if it remains as such
after its preparation, i.e., the dispersed globules are
uniformly distributed through out the dispersion
medium during its storage.
• Emulsion should be chemically stable and there
should not be any bacterial growth during its shelf
life.
• The following three changes usually occurs during
the storage of an emulsion:-
1. Cracking, 2. Creaming, 3. Phase inversion
06/05/2015
Faculty of Pharmacy, Omer Al-Mukhtar University,
Tobruk, Libya.
22

23. B. Colloids
• A disperse system consists essentially of one
component, the disperse phase, dispersed as particles
or droplets throughout another component, the
continuous phase.
• By definition, dispersions in which the size of the
dispersed particles is within the range of 1nm to
about 0.5 µm are termed as colloid.
06/05/2015
Faculty of Pharmacy, Omer Al-Mukhtar University,
Tobruk, Libya.
23

24. Colloidal classification or
types
• Colloidal systems are best classified into three groups,
1. Lyophilic Colloids: Systems containing colloidal
particles that interact to an appreciable extent with the
dispersion medium are referred to as lyophilic (solvent-
loving) colloids.
2. Lyophobic Colloids: The second class of colloids is
composed of materials that have little attraction, if any,
for the dispersion medium. These are the lyophobic
(solvent-hating) colloids.
3. Association Colloids: Association or amphiphilic,
colloids form the third group in this classification.
06/05/2015 24
Faculty of Pharmacy, Omer Al-Mukhtar University,
Tobruk, Libya.

25. Properties of colloids
06/05/2015 25
Faculty of Pharmacy, Omer Al-Mukhtar
University, Tobruk, Libya.

26. Stability of colloidal systems
• The presence and magnitude, or absence, of a charge on
a colloidal particle is an important factor in the stability
of colloidal systems.
• Stabilization is essential by two means
– 1. Providing the dispersed particles with an electric charge,
– 2.Surrounding each particle with a protective solvent
sheath that prevents mutual adherence when the particles
collide as a result of Brownian movement.
• Protective colloids and other agents used to stabilize
the colloidal systems
– Ex: Gelatin, Albumin, Acacia, Sodium oleate, Tragacanth
06/05/2015 26
Faculty of Pharmacy, Omer Al-Mukhtar University,
Tobruk, Libya.

27. Applications of colloids
• Colloids are extensively used for modifying the
properties of pharmaceutical agents.
• The most common property that is affected is the
solubility of a drug.
• However, colloidal forms of many drugs exhibit
substantially different properties when compared with
traditional forms of these drugs.
• Another important pharmaceutical application of
colloids is their use as drug delivery systems.
• The most often used colloid-type drug delivery system
include hydro gels, microspheres, micro emulsions,
liposome's, micelles, nanoparticles, and nanocrystals.
06/05/2015 27
Faculty of Pharmacy, Omer Al-Mukhtar University,
Tobruk, Libya.

28. C. Suspension
• Suspension are the biphasic liquid dosage form of
medicament in which the finely divided solid
particles ranging from 0.5 to 5.0 micron are dispersed
in a liquid or semisolid vehicle.
• The solid particles act as disperse phase whereas
liquid vehicle acts as the continuous phase.
• Suspension are generally taken orally or by parenteral
route.
• They are also used for external applications.
06/05/2015 28
Faculty of Pharmacy, Omer Al-Mukhtar University,
Tobruk, Libya.

29. 1. Flocculated suspension: The suspension are said to
be flocculated, when the individual particles are in
contact with each other and form a network like
structure.
2. Non-flocculated suspension: Whereas in case of
non-flocculated suspensions, the individual particle
exists as a separate entity.
06/05/2015
Faculty of Pharmacy, Omer Al-Mukhtar University,
Tobruk, Libya.
29
Types or classification of
suspensions

30. Properties of Suspension
• Uniform particle size: all particles behave alike and
produce consistent behavior for the suspension as a
whole.
• No particle-particle interaction: each particle
remains discrete with no aggregation or clumping.
• No sedimentation: drug particles are either
stationary or move randomly thought-out the
dispersion medium, so the drug is always uniformly
distributed.
06/05/2015
Faculty of Pharmacy, Omer Al-Mukhtar University,
Tobruk, Libya.
30

31. • A stable suspension can be redisperse homogeneously
with moderate shaking and can be easily poured
throughout its shelf life.
• The most stable pharmaceutical suspensions are
flocculated.
• The sedimented particles of a flocculated suspension can
be redispense easily at any time with only moderate
shaking.
• The non-flocculated suspension can be made stable by
decreasing the particle size of the suspended material or
by increasing the density and viscosity of the vehicle.
06/05/2015
Faculty of Pharmacy, Omer Al-Mukhtar University,
Tobruk, Libya.
31
Stability of suspensions

32. Applications of suspension
• Suspensions can be used as oral dosage form.
• Suspensions can applied topically for the skin.
• Suspensions can applied to mucous membrane
surfaces.
• Suspensions can be given parent rally by injection.
06/05/2015 32
Faculty of Pharmacy, Omer Al-Mukhtar University,
Tobruk, Libya.

33. THANK YOUE-mail: nanjwadebk@gmail.com
06/05/2015 33
Faculty of Pharmacy, Omer Al-Mukhtar University,
Tobruk, Libya.