Dispersion - Micelles

-These are formed from amphiphilic molecules
-Ex: Sodium Lauryl Sulfate in Water

Association Colloids AKA Micelles

A counterion; an ion of opposite charge to another in an electrochemical or ion transport system

Gegenion

How do we form micelles? What do we add?

Surfactants

Why do we add surfactants to form micelles?

It lowers surface tension

Relationship between Surface tension and Micelle formation

Inversely proportional

A type of surfactant that can be added to form micelles

Emulsifier like CMC (carboxymethylcellulose)

This is anionic

Carboxymethylcellulose

-DEC surface tension
-DEC interfacial tension
-INC cleaning power
-INC solubility of difficult-to-solubilize drugs

When we reach critical micelle concentration

Critical Micelle Concentration (CMC)

A property of surfactant; threshold at which we form micelles

-Oil in Water (O/W)
-Water in Oil (W/O)
-Multiple Emulsions (W/O/W)

Dispersed systems of Emulsions

-Oil
-Water
-Surfactant (to keep layers stabilized)

Ingredients to Form Emulsions

-Dilution Test
-Dye Test
-Conductivity Test

How to Determine Emulsion Type

The larger bulk of an emulsion; the denominator in a dispersed system (X/Y or X in Y) where we are referring to Y

Continuous phase

-Monomolecular film
-Multimolecular film
-Solid particle film

Surfactants/Surface Active Agent Types?

Formed by:
-Potassium Laurate
-Sodium Lauryl Sulfate
-Cethyltrimethylammonium bromide
-Sorbitan fatty acid esters
-Polyxethylene Sorbitan fatty acid esters
-Lecithin
-Cholesterol

Monomolecular Film

Formed by:
-Acacia
-Gelatin

Multimolecular Film

Formed by
-Bentonite
-Veegum

Solid Particle Film

-Anionic
-Cationic
-Nonionic

Classification of Surface Active Agents

Soaps need what?

-Oil
-Base (i.e. sodium hydroxide or potassium hydroxide)

3 parts Base and 1 part Oil

How to Formulate Soaps

Example of an Anionic Surface-Active Agent

-Sodium Lauryl Sulfate
-Sodium Oleate

Example of a Cationic Surface-Active Agent

Cetrimethyl Ammonium Bromide

Example of a Nonionic Surface-Active Agent

-Span 40 (Sorbitan Monopalmitate)
-Tween 40 (Polyethylene Sorbitan Monopalmitate)

What can we NOT mix?

Cationic surface-active agent and Anionic surface-active agent

-Bactericidal
-Toxic if taken internally**
-Resulting pH: 4-6

Cationic Surface-Active Agent Characteristics

-Solubility: Soluble in water
-pHL 10-11
-Color: Pale White

Anionic Surface-Active Agent Characteristics

-Non-toxic**
-Non-suscpetible to pH changes
-Solubility: Soluble in water AND oil (more versatile)

Nonionic Surface-Active Agent Characteristics

A nonionic surfactant that forms W/O emulsions (longer tail)

Span 40

A nonionic surfactant that forms O/W emulsions (bigger polar head)

Tween 40

-SO4-, Na+
-COO-, Na+

Hydrophilic Groups (polar head) **hydrophilic part has negative charge

-CH-
-CH2-
-CH3-
=CH-

Lipophilic Groups (nonpolar tails)

A carbohydrate gum that is soluble in water and forms O/W emulsions

Needs a preservative when formulating. Addition of alcohol causes this to precipitate

Acacia

Why is it necessary to add a preservative when formulating Acacia?

Susceptible to microbial attack

From an acid-treated precursor; has an isoelectric pH within 7-9

Gelatin A

From an alkali-treated precursors; has isoelectric point around 5

Gelatin B

-A mixture of phospholipids; a natural emulsifying agent
-Extensively used and produces O/W emulsions

Lecithin

A lipophilic natural emulsifier which forms W/O emulsions

Cholesterol

HLB - Values below 10

= Lipophilic Surfactant (no foaming)

HLB - Values above 10

= Hydrophilic Surfactant

A REVERSIBLE process of emulsion stability where droplets move to the top!!! (opposite of sedimentation)

Creaming

A REVERSIBLE process of emulsion stability where droplets come together; NO FUSING THO

Aggregation

An IRREVERSIBLE process of emulsion stability where particles separate

Breaking

-Used to remove low molecular impurities that are charged (+/-)
-Faster than regular dialysis
-Electric field is applied to separate charged impurities from colloidal particles

Electrodialysis

-The sol is placed in a compartment enclosed by dialysis membrane which is supported
-Suction is applied from the other side of the membrane
-Small molecules are removed while colloidal size molecules are retained

Ultrafiltration

-Dialysis is used in the "artificial kidney units", which remove urea, creatinine, uric acid, phosphate, and other metabolites and excess sodium and potassium chloride from the blood of uremic patients

Hemodialysis

-Lyophilic (love solvent)
-Lyophobic (hate solvent)
-Association Colloids (formed from amphiphilic molecules)

Classification of Colloids

This lyophobic colloid has antibacterial properties

Colloidal silver

This lyophobic colloid is used historically against gout

Colloidal gold

Ways we can prepare lyophobic colloids

-Colloid mills (grinding)
-Condensation methods (Heat it up and then evaporate the metal → cool it down to condense)

1. Magma (2-phase)
- Water in the particles
- Bentonite magma
2. Single phase
- Tragacanth gel, Carbomer gel

Types of Gels

Property of gels that means:
"They are very viscous when standing and they are ligands when agitated"

Thixotropic