Exam III Emulsion
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What is the definition of emulsion?
- A dispersion of immiscible liquids (polar and non-polar)
- Hetergenous system: immiscible liquid intimatly dispersed in another lquid in the form of droplets or globule (neither miscible nor soluble with vehicle)
What is the composition of emulsion?
- Dispersed phase: Internal phase, discontinuous
- Dispersed medium: External phase, continuous
- Emulsifying agent: Emulsifier, surfactant, wetting agent
What are the applications of Emulsions?
- Allow for a stable and homeogenous preparation mixtures of oils and aqueous drugs
- Liquid drug as minute particles rather than large globules
What are the advantages of emulsion for oral use?
- They mask the taste of the oil
- Enhance the absorption, oil as small globule are more digestable and absorbed
What is the advantage of an emulsion for topical use?
Can place the irritating compounds in the internal phase.
What does a surfactant agent do?
- Also called: Surface active agent
- Promote the lowering of interfacial tension between two immiscible liquids
- Facilitate the breaking up large globule into smaller globules
- Decreases the tendency for globule to join, or coalesce
What is the infacial tension?
Causes small drops to join or coalesce, forming one larger drop
WHat is the reduction of interfacial tension theory of emulsion?
- The emulsifier forms a spherical droplet around the internal phase
- Smallest surface area possible
What is the oriented-wedge or Electrical double layer theory of emulsion?
- The emulsifier forms layers surrounding the internal phase
- The emulsifiing agent, hydrophilic portion, and hydrophobic agent will ORIENT themselves into each phase producing electrical forces that repulse approaching droplets
- The phase in which the emulsifing agent is more soluble is going to be the external phase, or the continuous phase
What is the plastic or interficial-film theory of emulsion?
- Emulsifing agent surrounds the droplets of the internal phase as a thin layer adsorbed on the surface of the droplet
- Enough film-forming material must be available to coat the entire surface each drop of internal phase
Form hydrophilic colloids with water and favor preparation of o/w emulsion
What are examples of carbohydrate emulsifier?
WHat kind of emulsion dose protein pruduce?
What are examples of protein emulsion?
Define wetting or sufactant agents
- Contain hydrophilic and lipophilic
- The lipophilic portion in general accounting for the surface activity
What are colloidal clays?
Finely divided solid that will form o/w or w/o emulsion depending on which phase a larger volume
What are examples of colloidal clays
- Magnesium hydroxide
- Aluminum hydroxide
What are high molecular weight alcohol used for in emulsions?
- Thickening agents
- USed for external use only
What is the continental or dry gum method?
- 4:2:1 ratio (4ml oil, 2ml water, 1g emulsifier)
- OIL + GUM =hydrocoloid: Rapid tituration for a very short time to reduce globule size of internal phase
- Water phase adding all at once with rapid trituration until snapping sound is made = formation of primary emulsion (creamy white)
- Other liquid ingrediants are added with slow trituration
- Rinse the mortar and pestle to get rest of emulsion
What is the wet gum or English method of emulsion?
- Preparation of a mucilage: small quantity of water and gum with trituration until uniform
- Oil is added with small proportion with rapid trituration, will make thick and viscous mixture, which is the primary emulsion
- More water is added with rapid trituration
- Other ingredient are added
What is the bottle or forbes bottle or shaking method of emulsion?
- IS a variation of the dry gum metod
- Emulsifier + volitle oil with rapid shaking
- Water added rapid shaking makes the primary emulsion
What is the beaker method of emulsifing?
- Oil and water phase are made seperately with dissolved ingredients
- Each phase is heated 60 to 70 oc
- INTERNAL phase is stirred into the external phase
- Product is cooled
- Gentle and periodical stirring unteal cooled (congealed)
What is the auxiliary method of emulsifiing?
- Hand homogenizer will reduce globule of internal phase by forcing the mixture through small inlet orifice at a high pressure
- Mechanical stirrers (mixers)
What is the in situ soap method of emulsifing?
Calcium soap (w/o emulsion) = Ca hydroxide solution (lime water) + vegetable oil
What is the HLB system?
- Hydrophile/lipophile balance
- Decribe the characterisics of a sufactant based on its chemical structure (hydrophilic and lipophilic portion)
- Each emulsifing agent has a HLB number which indicative of the substances polarity
Are emulsion lipophilic or hydrophilic?
What does a low HLB number indicate?
- LOW = Lipophilic predominantly and less polar
- Useful for water in oil emulsions
What does a high HLB number indicate?
- HIGH = Hydrophilic and highly polar materials
- Useful for oil in water emulsions
What phase should the preservitive be added to?
What state should the preservative be presented in?
Presented in the un-ionized state (effective against bacteria) must be neither bound nor absorbed to any agent in the emulsion or container
What are the most satisfactory preservatives for emulsion?
What is frequently added to prevent rancidity of oils and fats?
When is the flavoring agents added to emulsion?
- MIxed with surfactant before addidtion to aqeous phase
- Use of cosolvent system to incorporate flavor
What are the facts about packaging/storage/labeling for emulsions?
- Tight containers
- Oral emulsions wide opening
- Squeeze bottle: topical liquid emulsions
- Tubes and pump containers: viscous creams
- Avoid extreme cold and hot will cause to go out of emulsion
- Label should include shake well
What are the three ways to enhance stability of emulsions?
- decrease globule size of the internal phase: by useing a shearing action of mortar and pestle or a hmogenizer
- TO have the optimun oil to water ratio with the internal phase be 40 percent of total product
- Increasing the viscosity of the system, add a substance that is soluble in or miscible wih the external phase
What is creaming instability process?
- The internal phase tend to form aggregates or globules upoon standing
- Aggregates may rise to the top of the emulsion or fall the bottom
- This is a reversible process and shaking amy redistribute creamed portion
What is coalescence instability process?
- Cracking or braking
- When the globules of the internal phase coalesce and this phase is separated into a layer
- This is an irrevesible process because the protection durrounding the globules of the internal phase is destroyed
- Additional emulsifying agent and reprocessing are usually necessary
What is phase inversion instability process?
From o/w to w/o or vice-versa
What are the facts about microemulsions?
- Biphasic oil/water system
- Optically transparent (solution like)
What are the HLB values for microemulsion?
What are the size of the droplets in a microemulsion?
- 100-5000 Angstrom
- 1 Angtrum= one ten-billonth of a meter
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