PPAR FINALS DISPERSED SYSTEM: COLLOIDAL AND COARSE DISPERSION

True Solutions (Molecular Dispersion)

Is defined as a mixture of two or more components that form a homogenous molecular dispersion or one phase system.

-*Not detected under ultra microscope and electron microscope

-Passed though ultrafilter and semi permeable

-Diffuse rapidly

Characteristics of True Solutions

-Visible under ultra microscope and electron microscope

-Passed though ultrafilter, however do not pass semi permeable membrane

-Diffuse very slowly

Colloidal Dispersion characteristics

colloidal silver soln, natural and synthetic polymers, cheese, butter, jelly, paint, milk, shaving cream

Colloidal Dispersion examples

Visible under ultra microscope and electron microscope-Do not pass through normal filter paper-Do not dialyze through semi permeable membrane-Do not diffuse

Coarse Dispersion Characteristics:

spherical

For colloidal particles, the geometry has been predominantly

1nm-0.5um

Colloidal Particles size

DIALYSIS

Colloidal Particles are separated by

•ULTRAFILTRATION

•ELECTRODIALYSIS - electronic potential across the membrane.

Colloidal Particles Purification Process:

ELECTRODIALYSIS PRINCIPLE

is an electrochemical process whereby electrically charged particles, ions, are transported from a raw solution (retentate, diluate) into a more concentrated solution (permeate, concentrate) through ion selective membranes by applying an electric field.

Nitrogen removal from drinking water (nitrate, ammonium)

Advantages of electrodialysis Applications for selective substance removal, as for example in

Advantages of electrodialysis

Desalination of organic substances

Concentration of salts, acids and base

Colloidal Silver Chloride, Silver Iodide and Silver protein

effective as GERMICIDES and do not cause the irritation that is characteristic of ionic silver salts.

Colloidal copper

has been used in the treatment of cancer

Colloidal gold

as a diagnostic agent for paresis

Colloidal mercury

used for for syphilis.

Colloidal Sulfur

used for medical imaging

-Proteins

-Starch (plant)

-Cellulose (plant)

Synthetic and Natural Polymers examples

Hydroxyethyl starch (HES)

a macromolecule used as a plasma substitute.

Dextran

Plasma expander

Colloidal electrolytes (Surface-active agents)

are sometimes used to increase the solubility, stability, and taste of certain compounds in aqueous and oily pharmaceutical preparations.

Lyophilic Colloids System

System containing colloidal particles that interact to an appreciable extent with dispersion medium

Examples of lyophilic colloids

organic molecules of gelatin, acacia, insulin, albumin, rubber, and polystyrene.

Lyophobic Colloids

Have little attraction to the dispersed medium.

-Absence of solvent sheath around the particle

Lyophobic Colloids

gold, silver, sulfur, arsenous sulfide and silver iodide.

Association colloids (Amphiphiles or surface active agents)

are characterized by having two distinct regions of opposing solution affinities within the same molecule or ion.

Association colloids

Micelles and the CMC Association

critical micelle concentration, or cmc.

The concentration of monomer at which micelles form is

aggregation number of the micelle

The number of monomers that aggregate to form a micelle is known as

SODIUM LAURYL SULFATE

Example of ANIONIC

CETYL TRIMETHYLAMMONIUM BROMIDE

Example of CATIONIC

POLYOXYETHYLENE LAURYL ETHER

example of NONIONIC

DIMETHYLDODECYLAMMONIOPROPANE SULFATE

Example of AMPHOLYTIC

Faraday Tyndall Effect

used for Optical

-Brownian Motion

- Diffusion

- Osmotic pressure

- Sedimentation

- Viscosity

- Electrokinetic phenomena

used for Kinetic

- Nernst Potential

- Zeta Potential

used for Electric

•1) Brownian motion

•2) Diffusion

•3) Osmosis

•4) Sedimentation

•5) Viscosity

•6) Electrokinetic phenomena

KINETIC PROPERTIES OF COLLOIDS

Brownian motion

-the random movement of colloidal particles

-resulting from the bombardment of the particles

-direct result of Brownian movement.

-This can be thermally induced

Osmosis

-Movement of solvent across a semi permeable membrane

-This can be thermally induced.

Sedimentation

-This is gravitationally induced.

-**ultracentrifuge

Viscosity

-an expression of the resistance of flow of a system under an applied stress.

-provide information regarding the shape of the particles in solution

Electrokinetic phenomena

- The movement of a charge surface with respect to an adjacent liquid phase is the basic principle underlying four electro kinetic phenomena

ELECTROPHORESIS

Involves the movement of charged particles through a liquid under the influences of an applied potential difference.

ELECTRO-OSMOSIS

-When movement of particles (electrophoresis) is prevented by some suitable means, it is observed that the dispersion medium begins to move in an electric field.-

electro-osmotic flow

-This motion disrupts the equilibrium symmetry of the particle's double layer

SEDIMENTATION POTENTIAL

-This causes a slight displacement between the surface charge and the electric charge of the diffuse layer.

-creates a dipole moment.

STREAMING POTENTIAL

-originates when an electrolyte is driven by a pressure gradient through a channel or porous plug with charged walls

STREAMING POTENTIAL

-displacement of the counterions in the free water produces a potential difference between the two ends of the tube

Nernst Potential

attract

•ELECTROTHERMODYNAMIC P

•difference in the potential between the actual surface of the particle and the electroneutral region of the dispersion

Zeta Potential

repel

•ELECTROKINETIC P

• difference in the potential between the surface of the tightly bound layer and the electroneutral region of the dispersion

•Greek letter zeta (ζ)

hydrophile (hydrophilic colloid)

The addition of large amounts of the _____________, however, stabilizes the system, the hydrophile being adsorbed on the hydrophobic particles.

protective colloid

This phenomenon is known as protection, and the added hydrophilic sol is known as the

an electric charge

Stabilization is accomplished essentially by Providing the dispersed particles with

protective solvent

Stabilization is accomplished essentially by two means of Surrounding each particle with a _____ sheath that prevents mutual adherence when the particles collide as a result of Brownian movement.

hydrophilic or hydrophobic colloid

The addition of a small amount of ______________- of opposite charge tends to sensitize or even coagulate the particles

gold number

The protective property is expressed most frequently in terms of

gold number

is the minimum weight in milligrams of the protective colloid (dry weight of dispersed phase) required to prevent a color change from red to violet in 10 mL of a gold sol on the addition of 1 mL of a 10% solution of sodium chloride.

Emulsions and aerosols

are thermodynamically unstable two phase systems which only reach equilibrium when the globules have coalesced to form one macro-phase, when the surface area is at a minimum.

flocculating or aggregating

Suspension particles achieve a lower surface area by _________; they do not coalesce

Brownian movement

reaming or sedimentation

convection

In dispersions of fine particles in a liquid (or of particles in a gas) frequent encounters between the particles occur due to:

particles resist flocculation or aggregation

When applied to colloids, a stable colloidal system is one in which the __________ and exhibits a long shelf life.

•Van der Waals forces or electromagnetic forces (attraction)

• Electrostatic forces (repulsion)

• Born forces – essentially short-range (repulsion

Forces of interaction between colloidal particles

Derjaguin, Landau, Verwey and Overbeek

DLVO Theory

Van der Waals and Electrostatic Repulsion

The primary forces, or potentials, that determine whether two particles in suspension will aggregate when they collide are

Hydration forces

For hydrophilic colloids, proteins, polysaccharides and liposome

Steric forces (repulsive)

due to adsorbed molecules (particularly macromolecules) at the particle interface

Solvation forces (repulsive)

due to reduction in the hydration of stabilizing molecules on close approach.

Ostwald Ripening

•Cause of particle Growth; results from the preferential creation of large particles at the expense of smaller ones.

•This can be accelerated by processes that alter dissolution

coarse suspensions

Deflocculation

sometimes peptization, The reversal of coagulation or flocculation, example is the dispersion of aggregates to form a colloidally stable suspension or emulsion

Perikinetic aggregation

If the collisions are caused by Brownian motion

Orthokinetic aggregation

If the collisions are caused by hydrodynamic motions

EMULSION

Coalescence

Creaming

Cracking Phase

Inversion

SUSPENSION

Aggregation

Sedimentation

Caking

Coacervation

The separation into two liquid phases in colloidal systems

Compaction

•A sedimentation where the concentration of particles is high and interparticle forces are strong enough.

•This particular kind of settling is also called subsidence.

Sediment

A highly concentrated suspension which may be formed by the sedimentation of a dilute suspension

Coalescence

The disappearance of the boundary between two particles

break/crack

•If coalescence is extensive it leads to the formation of a macrophase and the emulsion is said to

Microemulsions

form spontaneously when the components are mixed in the appropriate ratios and are thermodynamically stable. diameter 5–140 nm

Microemulsions

are homogeneous transparent systems of low viscosity which contain a high percentage of both oil and water and high concentrations (15 25%) of emulsifier mixture

Microemulsions

Maybe misnomer because it consists of larger or “swollen” micelles containing the internal phase, much like that found in a stabilized solution.

Microemulsion

•They appear as clear, transparent solutions, and thermodynamically stable.

Microemulsion

It contain droplets of oil in a water phase (o/w) or droplets of water in oil (w/o) with diameters of about 10 to 200 nm, and the volume fraction of the dispersed phase varies from 0.2 to 0.8

Microemulsion

has a very low interfacial tension

To achieve the very low interfacial tension → second amphiphile (the cosurfactant) eg, short-chain alcohol in the formulation. → incorporation into the interfacial film around the droplets

dispersed oil phase

crystalline gel phase

crystalline hydrate phase

dispersed oil phase

Stable oil-in-water creams prepared with ionic or non-ionic emulsifying waxes are composed of (at least) four phases

•Griseofulvin and indoxole

_______ in emulsion formulations exhibit enhanced oral absorption.

•The addition of electrolyte or drugs to intravenous fat emulsions is generally contraindicated because of the risk of destabilizing the emulsion.

plastic and pseudoplastic flow

Most emulsions display both ___ behaviour rather than simple Newtonian flow.

rheological properties

The pourability, spreadability and ‘syringeability’ of an emulsion will, however, be directly determined by its

GELS

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

thixotropic

gels may be

•semisolids on standing and becoming liquids on agitation

•semisolids on standing and becoming liquids on agitation

mostly less than 10% usually in 0.5 to 2.0%

The concentration of the gelling agents is ________ range, with some exceptions.

Jelly

when the coherent matrix is rich in liquid

Xerogel

When the liquid is removed and only the framework remains

Hydrogels

are gels that may contain water.

Organogels

are gels may contain an organic liquid.

SYNERESIS

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

SYNERESIS

observed in jellies and gelatin. The “bleeding” in connection with the liberation of oil or water from ointment bases usually results from a deficient gel structure rather than from the contraction involved in

SWELLING

is the taking up of liquid by a gel with an increase in volume.