Important Characteristics Of Deflocculated Suspensions

Important Characteristics Of Deflocculated Suspensions :

Ø In this suspension particles exhibit as separate entities.

Ø  Particle size is less as compared to flocculated particles. Particles settle

separately and hence, rate of settling is very low.

Ø  The sediment after some period of time becomes very closely packed, due to

weight of upper layers of sedimenting materials.

Ø After sediment becomes closely packed, the repulsive forces between particles

are overcomed resulting in a non-dispersible cake.

Ø More concentrated deflocculated systems may exhibit dilatant behavior.

Ø  This type of suspension has a pleasing appearance, since the particles are

suspended relatively longer period of time.

Ø  The supernatant liquid is cloudy even though majority of particles have been

settled.

Ø  As the formation of compact cake in deflocculated suspension, Brookfield

viscometer shows increase in viscosity when the spindle moves to the bottom of the

suspension.

Ø There is no clear-cut boundary between sediment and supernatant.

Flocculation is necessary for stability of suspension, but however flocculation affects bioavailability of the suspension. In an experiment by Ramubhau D et al., sulfathiazole suspensions of both flocculated and deflocculated type were administered to healthy human volunteers. Determination of bioavailability was done by urinary free drug excretion. From flocculated suspensions, bioavailability was significantly lowered than deflocculated suspension. This study indicates the necessity of studying bioavailability for all flocculated drug suspensions.