basic about supension

1. {
Suspensions
Suspensions are heterogeneous system
consisting of two phases.
The continuous or external phase is generally
a liquid or semisolid, and the dispersed or
internal phase is made up of particulate
matter that is essential insoluble in, but
dispersed throughout the continuous phase;

2. Based On General Classes
• Oral suspension
• Externally applied suspension
• Parenteral suspension
Classification

3. • Dilute suspension (2 to10%w/v solid)
• Concentrated suspension (50%w/v solid)
Based On Proportion Of Solid
Particles

4.  Flocculated suspension
 Deflocculated suspension
Based On Electrokinetic
Nature Of Solid Particles

5.  Colloidal suspension (< 1 micron)
 Coarse suspension (>1 micron)
 Nano suspension (10 ng)
Based On Size Of Solid
Particles

6. Evaluation of
Suspensions

7.  Sedimentation Method.
 Rheological Methods.
 Electrokinetic Techniques.
 Micrometric Method.
Methods of suspension

8.  The only emphasis here is on the most
pertinent aspects of suspension stability.
 Techniques for the evaluation of heterogenous
systems generally are complex and far from
being completely satisfactory.
Stability

9.  Use of evaluation techniques permits the formulator to
screen the initial preparations made and also to
compare the improved formulations to competitive
commercial products.
Stability

10.  Two method are studied for determination of
sedimentation
 Sedimentation volume
 Degree of flocculation
Sedimentation Method

11. Introduction
 Sedimentation means settling of particle or floccules
occur under gravitational force in liquid dosage form
Sedimentation Behavior

12.  The suspension formulation (50 ml) was poured
separately into 100ml measuring cylinders and
sedimentation volume was read after 1, 2, 3 and 7 days,
and thereafter weekly intervals for 12 weeks
 Triplicate results were obtained for each formulation
Sedimentation Volume

13.  Sedimentation volume was calculated according to the
equation
F=Vu/Vo
 Where, F= sedimentation volume
Vu= ultimate height of sediment
Vo= initial height of suspension
Sedimentation Volume

14.  It is a very useful parameter for flocculation
Degree of flocculation

15. {
Sedimentation Behavior of flocculated and
deflocculated suspension
Flocculated Suspensions
• 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.

16. The sedimentation depends not only on the
size of the flocs but also on the porosity of
flocs. In flocculated suspension the loose
structure of the rapidly sedimenting flocs
tends to preserve in the sediment, which
contains an appreciable amount of
entrapped liquid. The volume of final
sediment is thus relatively large and is
easily re dispersed by agitation.

18. {
Deflocculated suspensions
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’.

19. In deflocculated suspension larger
particles settle fast and smaller remain in
supernatant liquid so supernatant
appears cloudy whereby in flocculated
suspension, even the smallest particles
are involved in flocs, so the supernatant
does not appear cloudy

20. {
Brownian Movement
• Brownian movement of particle prevents
sedimentation by keeping the dispersed material in
random motion
• Brownian movement depends on the density of
dispersed phase and the density and viscosity of
the disperse medium

21. {
Brownian Movement
• The kinetic bombardment of particles by the
molecules of the suspending medium will keep the
particles suspending, provided that their size is
below critical radius “r”.
• Brownian movement can be observed, if particle
size is about 2 to 5 mm,
when the density of particle & viscosity of medium
are favorable.

22. {
Brownian Movement
The displacement or distance moved (Di) due to
Brownian motion is given by equation:
Where, R = gas constant
T = temp. in degree Kelvin
N = Avogadro’s number
η = viscosity of medium
t = time
r = radius of the particle
The radius of suspended particle which is increased
Brownian motions become less & sedimentation
becomes more important

23. {
Electrokinetic Properties
Zeta Potential:
• The zeta potential is defined as the difference in
potential between the surface of the tightly bound
layer (shear plane) and electro-neutral region of
the solution
• the potential drops off rapidly at first, followed by
more gradual decrease as the distance from the
surface increases
• This is because the counter ions close to the
surface acts as a screen that reduce the
electrostatic attraction between the charged
surface and those counter ions further away from
the surface

25. {
Zeta Potential
Zeta potential has practical application in stability of
systems containing dispersed particles since this
potential, rather than the Nernst potential, governs the
degree of repulsion between the adjacent, similarly
charged, dispersed particles. If the zeta potential is
reduced below a certain value (which depends on the
particular system being used), the attractive forces exceed
the repulsive forces, and the particles come together. The
flocculated suspension is one in which zeta potential of
particle is -20 to +20 mV.

26. {
Rheological Behavior
“Rheology is defined as the study of flow or
deformation of matter”.
The deformation of any pharmaceutical system can
be arbitrarily divided into two types:
• Spontaneous reversible deformation
• Irreversible deformation
The second one is of great importance in any liquid
dosage forms like suspensions, solutions,
emulsions.

27. {
Rheological behavior
• Brookfield viscometer is used to study the viscosity
of suspensions.
• It is mounted on heli path stand and T- bar spindle.
• T bar is made to descend slowly into the
suspension and dial reading on the viscometer and
is then measured.

28. T bar spindle

29.  The stability of suspension depends on the particle size of
the dispersed phase
 Change in the particle size with refrence to time will
provide useful information regarding the stability of
suspension.
 A change in particle size distribution and crystal habbit
studied by
 Microscopy
 Coulter counter method
MICROMIRETIC METHOD

32. REFRENCES
Industrial pharmacy by leon
lachman
Tutorial pharmacy
Remington