Emulsion Lec 1 PDF

EMULSION Definition: It is a thermodynamically unstable system consisting of two immiscible liquids, one of which is dispersed as globules in the other liquid, and it is stabilized by the presence of an emulsifying agent. Emulsion → Dispersed phase + Continuous phase + Emulsifying agent. The globul...

EMULSION Definition: It is a thermodynamically unstable system consisting of two immiscible liquids, one of which is dispersed as globules in the other liquid, and it is stabilized by the presence of an emulsifying agent. Emulsion → Dispersed phase + Continuous phase + Emulsifying agent. The globule diameter generally extends from about 0.1 to 10 um. Emulsion consistency: Low viscosity → lotions Highly viscous → ointments and creams Classification of Emulsion = Emulsion types 1. Simple Emulsion: Size of droplets 0.2 um - 100 um Oil in Water (O/W) Emulsion → topical or oral application. Water in Oil (W/O) Emulsion → topical application only. 2. Multiple Emulsions: Water-in-Oil-in-Water (W/O/W) Emulsion Oil-in-Water-in-Oil (O/W/O) Emulsion The use of multi emulsions is limited due to their possible reversion to the parent primary emulsions, e.g. O/W/O emulsion may revert to W/O emulsion. 3. Micro Emulsions: Size of droplets 10 - 200 nm O/W Micro Emulsions or W/O Micro Emulsions  General Uses of Emulsion Pharmaceutical Application: Due to the high bioavailability and absorption rate, it used in the pharmaceutical industry. Mostly it used for topical preparations like creams, lotions, etc. Cosmetic industry: There is a huge application of emulsion in the cosmetic industry. Example: creams, lotions, hair conditioners, etc. Food industry: Food products like milk, peanut butter, ice cream, etc. are some examples of emulsion. Paint industry: Examples like emulsion paints and inks. Fire extinguisher: used as a fire extinguisher.  Emulsions encountered in everyday life! Pesticides Asphalt Skin cream Metal cutting oils Margarine Ice cream Pharmaceutical applications of emulsion: 1- O/W emulsion used to mask the taste for the drug → drug in the internal phase and adding sweetening agent in the external phase. 2- For drugs with low aqueous solubility. In O/W emulsion the drug is dissolved in the internal phase, after oral administration → the oil + drug absorbed readily. (e.g., vitamins A, D, E, K) 3- Used to administer oils that having therapeutic effects e.g. liquid paraffin to treat constipation → O/W emulsion. 4- Used for drug is irritant topically it may be administered as an internal phase of an O/W emulsion. 5- O/W emulsions are most useful as water washable drug bases and for general cosmetics purposes. 6- W/O emulsions are employed more widely for the treatment of dry skin and emollient applications. 7- W/O emulsions have been employed to disperse water soluble antigenic materials in mineral oil for intramuscular depot injection. 8- W/O emulsions IM injection of certain water-soluble vaccines → slow release of the antigen → result in a greater antibody response → longer lasting immunity. 9- For total parenteral nutrition. 10- For patients who cannot swallow solid dosage forms. 11- Radio opaque emulsions used as diagnostic agents in X ray examinations. 12- The emulsifications are used in aerosol products to produce foams. 13- multiple emulsion W/O/W can be used as a sustained release dosage form. Characteristics of an acceptable emulsion: 1) Physically stable → No phase separation. 2) Sufficient flow properties → to be easily poured from container. 3) Must be easily spread over the affected area of skin (in case of external use). 4) Must be have pleasing, good odour and correct feel (in case of external use). Tests to identify the type of emulsion: 1- Conductivity Method 2- Phase Dilution Method 3- Dye Method 4- Fluorescence Method 5- Wetting of Filter Paper Method  1- Conductivity Method Principle: Most oils are poor conductors while aqueous systems are good conductors for electricity. Light bulb + an external electric source + 2 electrodes immersed in the emulsion. Result: ► When the light bulb glows → the emulsion is of the O/W type (since the water outer phase conducts electricity). ► When the light bulb not glow → emulsion W/O, the oil being the continuous phase, is a poor conductor of electricity.  2- Phase Dilution Method: Principle: The emulsion is readily diluted by the liquid which constitutes the continuous phase. Emulsion + few drops of water Result: Emulsion + few drops of water → miscible and homogenous → O/W type. Emulsion + few drops of water → immiscible → W/O type.  3- Dye Method: Principle: A addition of a colored dye soluble in one component, but insoluble in the other. Water soluble dye: amaranth (red), and brilliant blue. Oil soluble dye: red Sudan III. Emulsion + dye Result: If the color spreads through the whole emulsion → the phase in which the dye is soluble is the continuous one.  4- Fluorescence Method Principle: Many oils fluoresce under UV light. Drop of the emulsion → examination under fluorescent light microscope. Results: If the whole field fluoresces → the emulsion is W/O. If only a few fluorescent dots → the emulsion is O/W.  5- Wetting of Filter Paper Method Principle: It depends on the respective abilities of oil and water to wet filter paper. A drop of the emulsion is placed on a piece of filter paper. Results: If the liquid spreads rapidly → leaving a small crop at the center, the emulsion is O/W. If no spreading occurs → the emulsion is W/O. An ideal emulsifying agent must possess the following properties: 1- It should have surface activity → to be concentrated at the interface between oil and water. 2- It should be rapidly adsorbed at the interface and form a coherent film capable of preventing coalescence. 3- It should result in the formation of an electrical potential at the droplet surface to ensure repulsion between approaching droplets. 4- It should increase the viscosity of the emulsion. 5- It should be effective in a fairly low concentration.