In pharmacy, micromeritics is employed for: Release and Dissolution: Clinically, the particle size and surface area of a drug can affect its release from dosage forms administered orally, parenterally, rectally, and topically. Finely powdered drug has a high surface area, hence gets easily dissolved in dissolution fluids in vivo, thereby enhancing the drug solubility and
Pharmaceutical Applications of Micromeritics Read More »
Figure shows a schematic diagram of Coulter counter equipment used for determining the particle volume. The equipment is applicable to materials of particle size ranging between 0.5-1000μm. Principle The principle involved in the working of this instrument is that when the particles suspended in a conducting liquid passes through a small orifice (having electrodes on
Method for Determining Particle Volume Read More »
Emulsions are estimated for their flow behaviour. The flow related attributes desirable for the performance of an emulsion are: Removal of an emulsion from a bottle or tube. Flow of an emulsion through a hypodermic needle. Spreadability of an emulsion on the skin. Stress induced flow changes during manufacture (milling). Dilute emulsions possess Newtonian flow,
Rheological Properties of Emulsions Read More »
Stable emulsions can be produced by using emulsifying agents. These agents reduce the interfacial tension between the two phases and then separate the globules by creating a barrier at the interface. Surfactants are mainly used as emulsifying agents. The emulsifying agent’s solubility determines the kind of emulsion to be prepared. If using hydrophilic emulsifying agents
Emulsion Formulation by HLB Method Read More »
Emulsification is the method of dispersing a liquid in another immiscible liquid, The major groups of emulsifying agents are soaps, detergents, and compounds whose basic structure is a paraffin chain ending in a polar group. Bancroft stated that the essential conditions for a stable emulsion are that the drops of the dispersed phase should be
Theories of Emulsification – Pedagogy Zone Read More »
A biphasic liquid preparation containing two immiscible liquids, one of which is dispersed as minute globules into the other, is termed as pharmaceutical emulsion. The liquid in the form of minute globules is the dispersed phase, while the liquid containing the dispersed globules is the continuous phase. An emulsifying agent is added to disperse two
Emulsions : Introduction, Classification – Pedagogy Zone Read More »
Flocculated and deflocculated suspension: The formulation of a suspension possessing optimal physical stability depends on whether the particles in suspension are to be flocculated or to remain deflocculated. First approach involves use of a structured vehicle to keep deflocculated particles in suspension; a second depends on controlled flocculation as a means of preventing cake formation.
Formulations of Flocculated and Deflocculated Suspensions Read More »
Two important interfacial properties of suspensions are: The surface free energy, and The presence of electric charges on the surface of the dispersed particles. Surface Free Energy When solid or liquid materials are reduced in size, the surface area increases readily leading to corresponding increase in surface free energy given by: ΔF ∝ ΔA ΔA
Interfacial Properties of Suspended Particles Read More »
Flocculated and deflocculated suspension: The solid drug is crushed into smaller particles and then dispersed in a dispersion medium in order to prepare a suspension. As a result of crushing, the surface area of particles and their associated surface free energy increases. This makes the system thermodynamically unstable with highly energetic particles which regroup and
Flocculated and Deflocculated Suspensions Read More »
The dispersion system is categorised in the following three groups based on the size of dispersed particles: Molecular Dispersion: This system behaves as true solutions where the solute phase is present in the solvent phase. The solute (dispersed phase) is homogeneously distributed as separate molecules of size below 1nm (10-7 cm) throughout the solvent (dispersion
Classification of Dispersed Systems and Their General Characteristics Read More »