PhyPharm Sas 9-10

disperse or dispersion system

disperse or dispersion system

is a two-part system made up of microscopic or macroscopic particles and the medium in which they are suspended

dispersion medium

continuous phase, external phase

dispersed phase

internal phase

colloidal dispersion (colloid)

is a homogeneous or heterogeneous mixture that contains dispersed particles that are intermediate in size between those of a true solution and those of an ordinary heterogenous mixture

Dialysis

The colloidal particles are separated from the impurities (mainly electrolytes) by the diffusion through a porous membrane such as parchment, collodion, etc

Electrodialysis

A special case of dialysis, which is accelerated by the application of a potential difference across the membrane

Ultrafiltration

The colloidal particles are separated by the process of filtration, through a filter paper, which is impregnated with gelatin or collodion followed by hardening in formaldehyde

Ultra-centrifugation

Involves the separation of colloidal particles from the impurities by centrifugal force in which the colloidal solution is taken in a tube and placed in an ultra-centrifuge (tube is rotated at high speeds)

micelle

is an aggregate of surfactant or amphiphile molecules dispersed in a liquid, forming a colloidal suspension

Micelles

approximately spherical in shape although other shapes may form depending on the molecular geometry of their molecules and solution conditions.

Critical Micelle Concentration (CMC)

is defined as the concentration of surfactants above which micelles form and all additional surfactants added to the system will form micelles

Faraday-Tyndall Effect

Refers to the light scattering phenomenon that causes the path of a beam of light through a colloidal dispersion to be observable.

Electron Microscope

Capable of yielding pictures of actual particle sizes, shape and structure of colloidal particles

Light Scattering

Depend on Faraday-Tyndall effect. Use to give information about particles size & shape and for determination of molecular weights of colloids

Brownian Motion

The zig-zag movement of colloidal particles continuously and randomly.

Brownian Motion

Arises due to the uneven distribution of the collisions between colloid particles and the solvent molecules.

Brownian Motion

More rapid for smaller particles

Brownian Motion

Decreases with increasing viscosity of the medium

Diffusion

Particles diffuse readily spontaneously from a region of higher concentration to one of lower concentration until the concentration of the system is uniform throughout.

Diffusion

Fick's first law

Osmotic Pressure

Pressure that must be applied to the solution side to stop fluid movement when a semipermeable membrane separates a solution from pure water.

Sedimentation

Tendency for particles to settle out of the fluid in which they are entrained and come to rest against barrier

Sedimentation

Stoke's Law

Stoke's Law

the velocity at which a spherical particle will settle out of suspension (fall to bottom)

Viscosity

Resistance to flow of system under an applied stress. The more viscous a liquid, the greater the applied force required to make it flow at a particular rate

Zeta Potential

One of the fundamental parameters to affect stability. Gives detailed insight into the causes of dispersion's aggregation or flocculation. Can be applied to improve the formulation of dispersions.

Electrophoresis

Refers to the motion of charged particles to the fluid under the influence of an applied electric field. If an electric potential is applied to a colloid, the charged particles move toward the oppositely charged electrode. (Particles can move but not the medium)

Electroosmosis

Movement of dispersion medium under the influence of an electric field keeping the dispersed phase stationary. Motion of dispersion medium occurs towards one of the electrodes in an electric field and solid dispersed particle remain stationary. Liquid moves through a plug or a membrane across which a potential is applied (Medium can move but not particles)

Sedimentation Potential

Also known as Donnan Effect.

Streaming Potential

Potential difference at zero current produced by the convective flow of charge due to a pressure gradient (flow of liquid) through a charged capillary, membrane, plug, or diaphragm.

Colloids

are extensively used for modifying the properties of pharmaceutical agents.

Coarse dispersions

are characterized by relatively fast sedimentation of the dispersed phase caused by gravity or other forces

Coarse dispersion

A pharmaceutical suspension is a ____________ in which insoluble solid particles are dispersed in a liquid medium.

Sedimentation

refers to the settling of particles or floccules occur under gravitational force in liquid dosage form.

STOKE'S LAW

The rate of fall of a suspended particle in a vehicle of a given density is greater for larger particles than it is for smaller particles.

flocculation

is the formulation of clumps by the aggregation of fine particles in a suspension

deflocculation

is the dispersion of flocs in a suspension to form a stable colloid

flocculated

particles forms a loose aggregates ad form a network-like structure

deflocculated

particles exist as separate entities

Suspending agent

is a substance that is added to fluids to promote particle suspension or dispersion and reduce sedimentation.

emulsion

thermodynamically unstable system consisting of at least two immiscible liquid phases, one of which is dispersed as globules in the other liquid phase, stabilized by the presence of an emulsifying agent.

Flocculation

Clustering of individual dispersed droplets together, whereby the individual droplets do not lose their identity

Creaming

Occurs when isolated oil droplets combine and rise to the top of an oil in water emulsion

Sedimentation

Occurs when isolated water droplets combine and sink to the bottom of an water in oil emulsion.

Oswald Ripening

Growth of one emulsion droplet at the expense of a smaller one as a result of the difference in chemical potential of the material within the droplets.

Coalescence

Irreversible process by which two or more droplets merge during contact to form a single daughter droplet.

Phase Inversion

A phenomenon that occurs when agitated oil in water emulsion, reverts to a water in oil and vice versa.

Breaking or Phase Separation

Happens when homogenization of emulsion is not achieved (separation of oil and water phase in the system)

emulsifying agent (emulsifier)

is a surfaceactive ingredient or other type which adsorbs at the newly formed oil-water interface during emulsion preparation, and it protects the newly formed droplets against immediate recoalescence

Dilution Test

Based on the solubility of external phase of emulsion

Fluorescence Test

Based on the principle that oil glows in the presence of UV light.

Conductivity Test

Based on the principle that water is a good conductor of electricity and oil is not a conductor of electricity. Electrodes dipped into emulsion and connected to battery

Staining or Dye-Solubility Test

When an emulsion is mixed with a water-soluble or oil-soluble dye and observed under the microscope

Cobalt Chloride Test

When an emulsion is added to a dried filter paper soaked in cobalt chloride solution,

Microemulsions

appear as clear, transparent solutions, but unlike micellar solubilized systems, they may not be thermodynamically stable.

gel

is a solid or a semisolid system of at least two constituents, consisting of a condensed mass enclosing and interpenetrated by a liquid.

jelly

When the coherent matrix is rich in liquid, the product is often called

xerogel

When the liquid is removed and only the framework remains, the gel is known as a

Syneresis

When a gel stands for some time, it often shrinks naturally, and some of its liquid is pressed out.

Swelling

Taking up of liquid by a gel with an increase in volume.

Imbibition

Take up a certain amount of liquid without a measurable increase in volume

Rheology

is the study of flow of liquids, deformation of solids, and viscosity characteristics of powders, fluids, and semisolids

fluid

A form of matter that can flow from one place to another through any opening without showing any traits of rigidity.

liquid

A phase of matter which depends on the prevailing temperature and pressure of a particular substance

Viscosity

is an expression of the resistance of a fluid to flow; the higher the viscosity, the greater is the resistance.

Shear stress

refers to the force per unit area to bring about the flow.

Rate of shear

refers to the change in velocity over distance to bring about the flow.

Elasticity

is the ability of a material body to resist a distorting influence and to return to its original size and shape when that influence or force is removed

Fluidity

refers to the ability of a substance to flow or it is the reciprocal of viscosity

Absolute Viscosity

A phenomenon in which regardless of how much force of agitation or other methods of inducing shear stress applied to the liquid of interest, it will have the same viscosity value. Units: poise (P), centipoise (cP

Kinematic Viscosity

Defined as absolute viscosity divided by the density of the substance. Stoke (St), centistoke (cSt)

Relative Viscosity

Ratio of the viscosity of a solution to the viscosity of the solvent used. Unitless

Newtonian fluid

is a fluid in which the viscous stresses arising from its flow, at every point, are linearly correlated to the local strain rate—the rate of change of its deformation over time.

Rheogram

is a graphical representation of the rheological characteristics of a material, typically a graph of shear flow or rate of shear versus shear stress.

non-Newtonian fluid

is a fluid that does not follow Newton's law of viscosity in which viscosity can change when under force or stress to either more liquid or more solid

PLASTIC

Also known as Bingham Body. • Substance the exhibit yield value. • The yield value must overcome in order for the system to flow. • Requires a finite stress to start and maintain flow. • Curves does not pass through the origin but rather intersect the shearing stress axis at a particular point (yield value)

PLASTIC

Flocculated particles in suspensions • Drilling mud • Slurries • Toothpaste • Blood • Butter • Margarine

Pseudoplastic

Also known as "shear-thinning" system. • No yield value. • The viscosity decreases with increasing rate of shear. • Curve begins at the origin.

Pseudoplastic

• Natural and synthetic gums • Liquid dispersion of tragacanth • Sodium alginate • Methylcellulose • Pentylcellulose • Sodium carboxymethyl cellulose • Polymer solutions • Polyethylene glycol • Ketchup

Dilatant

Also known as "shear-thickening" system. • The viscosity increases with increasing rate of shear. • Increase in volume when sheared. • Reverse effect of pseudoplastic. • When stress is removed, it returns to its original state of fluidity. • As shear stress is increased, the bulk of the system expands or dilates

DILATANT

• Certain deflocculated suspensions with a high percentage of dispersed solids (50 % or greater). • Paint • Whipped cream • Corn starch or starch in water • Clay slurries • Concentrated suspension of inorganic pigments in water • ZnO2 in water • BaSO4 in water • TiO2 in water

Thixotropy

Decrease in viscosity as a function of time upon shearing, then recovery of original viscosity as a function of time without shearing. • An isothermal and comparatively slow recovery on standing of a material of a consistency lost through shearing. • Viscosity decreases as stress is applied over time. • Started at pseudoplastic through time. • Reversible gel-to-sol transformation.

THIXOTROPY

Honey • Paint • Asphalt • Yoghurts • Mayonnaise • Ketchup

Rheopexy

Also known as anti-thixotropy or negative thixotropy. • Increase in viscosity as a function of time upon shearing, then recovery of original viscosity as a function of time without shearing. • Viscosity increases as stress is applied over time. • sol-to-gel transformation

Rheopexy

Printer ink • Magnesia Magma • Bentonite Clay suspension • Gypsum paste