PPF 633: Pharmaceutical Product Formulation EMULSIONSINTROUCTION:An emulsion is a thermodynamically unstable two phase system consisting of at leasttwo immiscible liquids, one of which is dispersed in the form of small droplets throughout the other and stabilized by an emulsifying agent. The dispersed liquid is the internal or discontinuous phase, whereas the dispersion medium is the external or continuous phase.-reluctance to mix has to be overcome-occur naturally, eg. milk-thermodynamically unstable solution-3 phases: aqueous phase, lipophilic phase, emulsifier-dispersed as droplets not particlesOilWaterTwo phase system: completely immiscibleOilE / A (Emulsifying Agent)WaterEmulsifying Agent: Stabilize the O / W phase. Note – mechanism of action1. Dispersed phase1
2. Continuous phase or dispersion medium A stable emulsion is dependent on proper blend of the aqueous phase, the oily phase and the emulsifiersWe can prepare an emulsionby shaking together or blending two immiscible liquids. This breaks one liquid into droplets of colloidal size, which then disperse throughout the other liquid. Oil spills in the ocean may be difficult to clean up, partly because wave action can cause the oil and water to form an emulsion. In many emulsions, however, the dispersed phase tends to coalesce, form large drops, and separate. Therefore, emulsions are usually stabilized by an emulsifying agent, a substance that inhibits the coalescence of the dispersed liquid. For example, a little soap will stabilize an emulsion of kerosene in water. Milk is an emulsion of butterfat in water, with the protein casein as the emulsifying agent. Mayonnaise is an emulsion of oil in vinegar, with egg yolk components as the emulsifying agents.Note: Phase volume ratioExplainO/W or W/OEmulsiona. With oilthe dispersephase and waterthe continuousphaseOil in water emulsion (O/W)b. With waterthe dispersephase and oilthe continuousphaseWater in oil emulsion (W/O)c. Multiple emulsions: W/O/W and O/W/OWhere oils, petroleum hydrocarbons, and / or waxes are the dispersed phase, and water or an aqueous solution is the continuous phase, the system is called an oil-in-water (o/w) emulsion.O/W emulsionis generally formed if the aqueous phase constitutes > 45% of the total weight, and a hydrophilic emulsifieris used.2
if water is >45% than W/OO/W emulsionsare miscible with water, are water washable, will absorb water, are non-occlusive, and are non-greasy. Here water is the external phase and will readily associate with any of the actions of waterConversely, where water or aqueous solutions are dispersed in an oleaginous medium, the systemis known as water-in-oil (w/o) emulsion.W/O emulsionsare generally formed if the aqueous phase constitutes < 45% of the total weight and a lipophilic emulsifieris used.
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- Fall '17
- Emulsion, HLB