Disperse Systems and Suspensions Flashcards

Vocabulary practice flashcards covering definitions, terminology, electrical double layer properties, DLVO theory, and sedimentation behavior in pharmaceutical disperse systems and suspensions.

Disperse system

A system in which one component (the dispersed phase) is dispersed through another (the continuous phase), where the individual phases do not change state.

Lipophilic

Having an affinity for, tending to combine with, or capable of dissolving in lipids.

Hydrophilic

Having an affinity for, tending to combine with, or capable of dissolving in aqueous systems.

Lyophobic

Having an aversion for the continuous solvent type.

Lyophilic

Having an affinity for the continuous solvent type.

Colloidal suspension

A suspension system in which the dispersed solid particles have a diameter up to $1\text{ }\bar{\text{m}}\text{m}$ (specifically up to $1\text{ }\bar{\text{m}}\text{m}$ in particle size).

Coarse dispersion

A suspension system in which the dispersed solid particles have a size greater than $1\text{ }\bar{\text{m}}\text{m}$.

Pharmaceutical suspension

A liquid system consisting of solid drug particles dispersed throughout an insoluble liquid phase, with typical particle sizes ranging from $0.1\text{ }\bar{\text{m}}\text{m}$ to $10\text{ }\bar{\text{m}}\text{m}$.

Chloramphenicol palmitate

An insoluble form of chloramphenicol formulated into an oral suspension to mask the unpleasant taste of the soluble drug form.

Stern layer

The fixed inner layer of strongly attached counter-ions immediately adjacent to a charged particle surface within the electrical double layer.

Diffuse layer

The outer region of an electrical double layer where mobile ions decay in concentration toward the bulk solution.

Zeta potential

The electrical potential existing at the slipping or shear plane between the moving particle with its attached layer and the bulk liquid phase.

DLVO theory

A theory describing particle interaction where total potential energy ($V_T$) is the additive sum of van der Waals attractive forces ($V_A$) and electrostatic repulsive forces ($V_R$): $V_T = V_A + V_R$.

Primary minimum

A deep minimum in total potential energy at close particle distance where attractive forces dominate, leading to initial flocculation and subsequent coagulation.

Primary maximum

An energy barrier in DLVO theory where electrostatic repulsive forces exceed attractive forces, preventing particle collision and maintaining deflocculation.

Secondary minimum

A shallow energy minimum occurring at larger inter-particulate distances where weak attractive forces produce loose aggregates (floccules), representing the desired state for pharmaceutical suspensions.

Coagulation

An undesirable process where suspended particles collide and adhere closely to form larger permanent aggregates at the primary potential energy minimum.

Deflocculation

A state in which individual particles remain separate from one another due to repulsive forces exceeding attractive forces at the primary energy maximum.

Brownian motion

Random thermal motion relevant for suspended particles up to $1\text{ }\bar{\text{m}}\text{m}$ to $2\text{ }\bar{\text{m}}\text{m}$ in size that aids diffusion and improves dosage uniformity.

Stokes' equation

The equation determining gravitational sedimentation velocity ($v$) for particles larger than $0.5\text{ }\bar{\text{m}}\text{m}$: $v = \frac{d^2 g (\rho - \rho_0)}{18 \nu}$.