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All suspensions, including coarse emulsions, are inherently thermodynamically unstable. They will, through random motion of the particles over time, aggregate because of the natural and dominant tendency to decrease the large specific surface area and excess surface energy.
How are suspensions thermodynamically stable?
In order to maintain the highest degree of suspension stability, the forces of attraction must be kept as low as possible and there must be sufficiently repulsive force to counteract them.
What are the causes of instability of suspension?
Increasing the viscosity – increasing the viscosity of the continuous phase can lead to the stability of suspensions. This is so because the rate of sedimentation can be reduced by increase in viscosity. Viscosity increase is brought about by addition of thickening agents to the external phase.
How can drug stability be improved?
To more optimally exploit the potential of PM for targeted drug delivery, several physical (e.g. π-π stacking, stereocomplexation, hydrogen bonding, host-guest complexation and coordination interaction) and chemical (e.g. free radical polymerization, click chemistry, disulfide and hydrazone bonding) strategies have Jul 14, 2016
Is suspension more stable than solution?
Finally, drugs in suspension are chemically more stable than in solution. This is particularly important with certain antibiotics and the pharmacist is often called on to prepare such a suspension just prior to the dispensing of the preparation.
What is the size of suspended drug having the range of?
Pharmaceutical suspension may be defined as coarse dispersions in which insoluble solids are suspended in a liquid medium. Insoluble solids may have a size range from 10 to 1000 µm. It is important to understand that suspensions are kinetically stable, but thermodynamically unstable, system.
Why suspension is unstable Class 9?
Suspension is a heterogeneous Mixture. The particles of a suspension scatter a beam of light passing through it and make its path visible. • The solute particles settle down when a suspension is left undisturbed, that is, a suspension is unstable.
Which suspension is more stable and why?
Suspension is more stable. This is because suspension does not mix with each other. The denser particles settle down at the bottom and makes the solution stable.
How do you increase suspension stability?
There are some useful methods to improve the physical stability of a suspension, such as decreasing the salt concentration, addition of additives to regulate the osmolarity, as well as changes in excipient concentrations, unit operations in the process, origin and synthesis of the drug substance, polymorphic behavior
What is the major stability problem related to the suspension?
The main problem dealt with in this article is preventing the aggregation of particles in a suspension — extensive aggregation can lead to ‘caking’. This is the process in which almost all particles in the sediment become interconnected, making it impossible to resuspend.
What are the roles of suspending agents in suspension stability?
Suspending agents form film around particle and decrease interparticulate attraction. At rest the solution is sufficient viscous to prevent sedimentation and thus aggregation or caking of the particles. When agitation is applied the viscosity is reduced and provide good flow characteristic from the mouth of bottle.
Is a suspension stable?
Suspension Stability Increasing the zero-shear viscosity of the continuous phase of an emulsion or suspension is a popular method of increasing physical stability. Controlled stress measurements on high performance rheometers are a necessity for zero-shear viscosity testing.
Does suspension show Tyndall effect?
The Tyndall effect is the scattering of visible light by colloidal particles. Suspensions may scatter light, but if the number of suspended particles is sufficiently large, the suspension may simply be opaque and the light scattering will not occur.
Why are suspensions not stable?
When suspension is left for some time, particles get settled in bottom. Therefore, suspension is not stable.
What factors affect suspension?
Factors affecting rheology of a suspension
- Dispersed phase content. The content of the dispersed phase φ is the most important physical parameter that affects the viscosity of dispersions.
- Particle shape. Particle shape can affect the rate of sedimentation as well as the viscosity of suspensions.
- Particle size and size distribution.
- Temperature.
Which is more stable colloid or suspension?
and Suspension is unstable. Colloid particles are also small but larger than true solution(1nm to 100nm) so they also mix and do not settle at the bottom. But in suspension the particles are quite large (larger than 100nm) so they do not mix and settle at the bottom so they are unstable.
What is suspending agent?
: a substance (such as carrageenan, xanthan gum, or cellulose ether) that is added to fluids to promote particle suspension or dispersion and reduce sedimentation All these drinks can contain preservatives, and drinks other than juices can contain additives to colour, flavour and sweeten.
What is Tyndall effect class 9?
Tyndall effect, also called Tyndall phenomenon, scattering of a beam of light by a medium containing small suspended particles—e.g., smoke or dust in a room, which makes visible a light beam entering a window.
What is the stability of suspension?
Suspension stability can be theoretically estimated prior to the beginning of the formulating process based on the solid phase particle size, liquid phase density, and viscosity. In order to prevent formation of the solid sediment, controlled flocculation of the suspended bismuth subnitrate particles is recommended.
What is the stability of true solution?
| Properties | True solution | Colloids |
|---|---|---|
| Stability | Solution is stable as the solute particles do not settle down when left undisturbed. | Stable |
How suspension is unstable?
The suspension is unstable. The particles of a suspension settle down after some time. A suspension scatters a beam of light passing through it because of its large particle size.
Why are suspensions unstable whereas colloidal solutions are stable?
Answer: The colloidal particles are smaller and not heavy. Apart from this, colloidal particles are charged and repel each other. This fact also do not the particles of colloidal solution to settle down. Whereas particles of suspension are larger, heavy and have less movement, thus settle down due to gravity.
Which cation is most stable?
(CH3)3C+3∘ carbonium ion is most stable.
How can you prevent suspension from sedimentation?
Slow down sedimentation by increasing viscosity of continuous phase. Velocity increases with the square of particle size making this the most critical parameter. For concentrated systems a crowding factor must be introduced which incorporates the phase volume Φ.
Is suspension can improve the chemical stability of a drug?
Suspension can improve chemical stability of certain drug. For example Procaine penicillin G. Drug in suspension exhibits higher rate of bioavailability than other dosage forms. Suspension can mask the unpleasant/bitter taste of drug.
