1. Pharmacy Practice 1 Dr. Muslim Suardi, MSi., Apt. Faculty of Pharmacy University of Andalas Emulsion

2. Emulsion “A thermodynamically unstable two- phase system consisting of at least two immiscible liquids, one of which is dispersed in the form of small droplets throughout the other, & an emulsifying agent” An emulsion is a thermodynamically unstable two-phase system consisting of at least two immiscible liquids, one of which is dispersed in the form of small droplets throughout the other, and an emulsifying agent. The dispersed liquid is known as the internal or discontinuous phase, whereas the dispersion medium is known as the external or continuous phase. Where 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. An o/w emulsion is generally formed if the aqueous phase constitutes > 45% of the total weight, and a hydrophilic emulsifier is used. Conversely, where water or aqueous solutions are dispersed in an oleaginous medium, the system is known as a water-in-oil (w/o) emulsion. W/O emulsions are generally formed if the aqueous phase constitutes < 45% of the total weight and an lipophilic emulsifier is used.

3. Phase of Emulsion Internal phase Internal phase Discontinuous phase: Dispersed liquid External phase External phase Continuous phase: Dispersion medium

4. Oil-in-Water Emulsion Dispersed phase: Oils, petroleum hydrocarbons, waxes Dispersed phase: Oils, petroleum hydrocarbons, waxes Continuous phase: water or an aqueous solution. O/W emulsion: generally formed if the aqueous phase constitutes > 45% of the total weight, & a hydrophilic emulsifier is used. O/W emulsion: generally formed if the aqueous phase constitutes > 45% of the total weight, & a hydrophilic emulsifier is used.

5. Water-in-Oil Emulsion Water or aqueous solutions are dispersed in an oleaginous medium. Water or aqueous solutions are dispersed in an oleaginous medium. Generally formed if the aqueous phase constitutes <45% of the total weight & an lipophilic emulsifier is used. Generally formed if the aqueous phase constitutes <45% of the total weight & an lipophilic emulsifier is used.

6. Usage of Emulsions Many routes of administration. Many routes of administration. Oral administration can be used, but patients generally object to the oily feel of emulsions in the mouth. Oral administration can be used, but patients generally object to the oily feel of emulsions in the mouth. Some times, emulsions are choosed to mask the taste of a very bitter drug or when the oral solubility or BA of a drug is to be dramatically increased Some times, emulsions are choosed to mask the taste of a very bitter drug or when the oral solubility or BA of a drug is to be dramatically increased

7. Topical Emulsions Creams: Have emollient properties. Have emollient properties. Can be o/w or w/o & are generally opaque, thick liquids or soft solids. Can be o/w or w/o & are generally opaque, thick liquids or soft solids. Emulsions are also the bases used in lotions, as are suspensions. Emulsions are also the bases used in lotions, as are suspensions.

8. Lotion Not an official term, but is most often used to describe fluid liquids intended for topical use. Not an official term, but is most often used to describe fluid liquids intended for topical use. Lotions have a lubricating effect. Lotions have a lubricating effect. Intended to be used in areas where the skin rubs against itself such as between the fingers, thighs, & under the arms. Intended to be used in areas where the skin rubs against itself such as between the fingers, thighs, & under the arms.

9. Usage of Emulsions Also used a ointment bases & IV-ly administered as part of parenteral nutrition therapy. Also used a ointment bases & IV-ly administered as part of parenteral nutrition therapy. Their formulation & uses in these roles will be covered in the appropriate chapters. Their formulation & uses in these roles will be covered in the appropriate chapters.

10. Consistency of Emulsions Varies from easily pourable liquids to semisolid creams. Varies from easily pourable liquids to semisolid creams. Consistency will depend upon: Consistency will depend upon: Internal phase volume to external phase volume ratio in which phase ingredients solidify what ingredients are solidifying

11. Vanishing Creams Stearic acid creams are o/w emulsions & have a semisolid consistency but are only 15% internal phase volume. Stearic acid creams are o/w emulsions & have a semisolid consistency but are only 15% internal phase volume. Many emulsions have internal phases that account for 40% - 50% of the total volume of the formulation. Many emulsions have internal phases that account for 40% - 50% of the total volume of the formulation. Any semisolid character with w/o emulsions generally is attributable to a semisolid external phase Any semisolid character with w/o emulsions generally is attributable to a semisolid external phase

12. W/O Emulsions Tend to be immiscible in water, not water washable, will not absorb water, are occlusive, & may be "greasy." Tend to be immiscible in water, not water washable, will not absorb water, are occlusive, & may be "greasy." This is primarily because oil is the external phase, & oil will repel any of the actions of water. This is primarily because oil is the external phase, & oil will repel any of the actions of water. Occlusiveness is because the oil will not allow water to evaporate from the surface of the skin. Occlusiveness is because the oil will not allow water to evaporate from the surface of the skin.

13. O/W Emulsions Miscible with water, are water washable, will absorb water, are nonocclusive, & are nongreasy. Miscible with water, are water washable, will absorb water, are nonocclusive, & are nongreasy. Water is the external phase & will readily associate with any of the actions of water Water is the external phase & will readily associate with any of the actions of water

14. Emulsions Instability By nature, physically unstable By nature, physically unstable Tend to separate into 2 distinct phases or layers over time. Tend to separate into 2 distinct phases or layers over time.

15. Instability Creaming: Creaming: Dispersed oil droplets merge & rise to the top of an o/w emulsion or settle to the bottom in w/o emulsions. Emulsion can be easily redispersed by shaking. Emulsion can be easily redispersed by shaking.

16. Instability Coalescence Coalescence Breaking or cracking: complete & irreversible separation & fusion of the dispersed phase. Phase inversion Phase inversion Change from w/o to o/w (or vice versa) may occur.

17. Emulsifying Agents Emulsions are stabilized by adding an emulsifier. Emulsions are stabilized by adding an emulsifier. Have a hydrophilic & a lipophilic part in their chemical structure. Have a hydrophilic & a lipophilic part in their chemical structure. All emulsifying agents concentrate at & are adsorbed onto the oil:water interface to provide a protective barrier around the dispersed droplets. All emulsifying agents concentrate at & are adsorbed onto the oil:water interface to provide a protective barrier around the dispersed droplets. In addition to this protective barrier, emulsifiers stabilize the emulsion by reducing the interfacial tension of the system. In addition to this protective barrier, emulsifiers stabilize the emulsion by reducing the interfacial tension of the system.

18. Emulsifying Agents Enhancing stability by imparting a charge on the droplet surface thus reducing the physical contact between the droplets & decreasing the potential for coalescence. Enhancing stability by imparting a charge on the droplet surface thus reducing the physical contact between the droplets & decreasing the potential for coalescence. Commonly used: tragacanth, Na lauryl sulfate, Na dioctyl sulfosuccinate, & polymers known as the Spans® & Tweens®. Commonly used: tragacanth, Na lauryl sulfate, Na dioctyl sulfosuccinate, & polymers known as the Spans® & Tweens®.

19. Emulsifyer Classification Chemical structure: synthetic, natural, finely dispersed solids, & auxiliary agents. Chemical structure: synthetic, natural, finely dispersed solids, & auxiliary agents. Mechanism of action: monomolecular, multimolecular, & solid particle films. Mechanism of action: monomolecular, multimolecular, & solid particle films.

20. Emulsifier Requirement Regardless of their classification, all emulsifiers must be chemically stable, inert & chemically non-reactive with other emulsion components, nontoxic & nonirritant. Regardless of their classification, all emulsifiers must be chemically stable, inert & chemically non-reactive with other emulsion components, nontoxic & nonirritant. They should also be reasonably odorless & not cost prohibitive They should also be reasonably odorless & not cost prohibitive

22. Synthetic Emulsifiers Cationic Cationic Anionic Anionic Nonionic Nonionic

23. Synthetic Emulsifiers Cationic & anionic surfactants are generally limited to use in topical, o/w emulsions. Cationic & anionic surfactants are generally limited to use in topical, o/w emulsions. Cationic: Cationic: Benzalkonium chloride Benzethonium chloride

24. Cationic Agents Quarternary ammonium salts Incompatible with organic anions Incompatible with organic anions Infrequently used as emulsifiers. Soaps are subject to hydrolysis & may be less desirable than the more stable detergents. Infrequently used as emulsifiers. Soaps are subject to hydrolysis & may be less desirable than the more stable detergents.

25. Anionic Alkali soaps: Alkali soaps: Na or K oleate Amine soaps Amine soaps TEA stearate; Detergents: Na lauryl sulfate, Na dioctyl sulfosuccinate, Na docusate).

26. Nonionic Sorbitan esters (Spans®) Sorbitan esters (Spans®) Polyoxyethylene derivatives of sorbitan esters (Tweens®) Polyoxyethylene derivatives of sorbitan esters (Tweens®) Glyceryl esters Glyceryl esters

27. Natural Emulsifier A variety of emulsifiers are natural products derived from plant/animal tissue. A variety of emulsifiers are natural products derived from plant/animal tissue. Most of the emulsifiers form hydrated lyophilic colloids (called hydrocolloids) that form multimolecular layers around emulsion droplets. Most of the emulsifiers form hydrated lyophilic colloids (called hydrocolloids) that form multimolecular layers around emulsion droplets.

28. Hydrocolloid Emulsifiers Have little/no effect on interfacial tension, but exert a protective colloid effect, reducing the potential for coalescence, by: Providing a protective sheath around the droplets Providing a protective sheath around the droplets Imparting a charge to the dispersed droplets (so that they repel each other) Imparting a charge to the dispersed droplets (so that they repel each other) Swelling to increase the viscosity of the system (so that droplets are less likely to merge) Swelling to increase the viscosity of the system (so that droplets are less likely to merge)

29. Classification of Hydrocolloid Emulsifiers Vegetable derivatives: acacia, tragacanth, agar, pectin, carrageenan, lecithin Vegetable derivatives: acacia, tragacanth, agar, pectin, carrageenan, lecithin Animal derivatives: gelatin, lanolin, cholesterol Animal derivatives: gelatin, lanolin, cholesterol Semi-synthetic agents: methylcellulose, CMC Semi-synthetic agents: methylcellulose, CMC Synthetic agents: Carbopols® Synthetic agents: Carbopols®

30. Naturally Plant Hydrocolloids Advantages: inexpensive, easy to handle, & nontoxic. Advantages: inexpensive, easy to handle, & nontoxic. Disadvantages: require relatively large quantities to be effective as emulsifiers, subject to microbial growth & thus their formulations require a preservative. Disadvantages: require relatively large quantities to be effective as emulsifiers, subject to microbial growth & thus their formulations require a preservative. Vegetable derivatives are generally limited to use as o/w emulsifiers. Vegetable derivatives are generally limited to use as o/w emulsifiers.

31. The Animal Derivatives General form w/o emulsions. General form w/o emulsions. Lecithin & cholesterol form a monomolecular layer around the emulsion droplet instead of the typically multimolecular layers. Lecithin & cholesterol form a monomolecular layer around the emulsion droplet instead of the typically multimolecular layers. Cholesterol is a major constituent of wool alcohols & it gives lanolin the capacity to absorb water & form a w/o emulsion. Cholesterol is a major constituent of wool alcohols & it gives lanolin the capacity to absorb water & form a w/o emulsion.

32. Lecithin A phospholipid derived from egg yolk A phospholipid derived from egg yolk Produces o/w emulsions because of its strong hydrophilic character. Produces o/w emulsions because of its strong hydrophilic character. Animal derivatives are more likely to cause allergic reactions & are subject to microbial growth & rancidity. Animal derivatives are more likely to cause allergic reactions & are subject to microbial growth & rancidity. Advantage: in their ability to support formation of w/o emulsions Advantage: in their ability to support formation of w/o emulsions

33. Semi-synthetic Agents Stronger emulsifiers, nontoxic, & less subject to microbial growth. Stronger emulsifiers, nontoxic, & less subject to microbial growth. Synthetic hydrocolloids: strongest emulsifiers, nontoxic, not support microbial growth. Synthetic hydrocolloids: strongest emulsifiers, nontoxic, not support microbial growth. Cost may be prohibitive. Cost may be prohibitive. Generally limited to use as o/w emulsifiers. Generally limited to use as o/w emulsifiers.

34. Natural Emulsifiers Derived from plant or animal tissue. Derived from plant or animal tissue. Most of them form hydrated lyophilic colloids (called hydrocolloids) that form multimolecular layers around emulsion droplets. Most of them form hydrated lyophilic colloids (called hydrocolloids) that form multimolecular layers around emulsion droplets.

35. Hydrocolloid Emulsifiers Little/no effect on interfacial tension, but exert a protective colloid effect, reducing the potential for coalescence, by: Little/no effect on interfacial tension, but exert a protective colloid effect, reducing the potential for coalescence, by: Providing a protective sheath around the droplets Providing a protective sheath around the droplets Imparting a charge to the dispersed droplets (so that they repel each other) Imparting a charge to the dispersed droplets (so that they repel each other) Swelling to increase the viscosity of the system (so that droplets are less likely to merge) Swelling to increase the viscosity of the system (so that droplets are less likely to merge)

36. Hydrocolloid Emulsifiers Classification Vegetable derivatives: acacia, tragacanth, agar, pectin, carrageenan, lecithin Vegetable derivatives: acacia, tragacanth, agar, pectin, carrageenan, lecithin Animal derivatives: gelatin, lanolin, cholesterol Animal derivatives: gelatin, lanolin, cholesterol Semi-synthetic agents: Methylcellulose, CMC Semi-synthetic agents: Methylcellulose, CMC Synthetic agents, e.g., Carbopols® Synthetic agents, e.g., Carbopols®

37. Plant Hydrocolloids Advantages Advantages Inexpensive, easy to handle, & nontoxic. Disadvantages Disadvantages Require relatively large quantities to be effective as emulsifiers Subject to microbial growth, require a preservative. Subject to microbial growth, require a preservative. Generally limited to use as o/w emulsifiers.

38. Animal Derivatives Animal Derivatives General form w/o emulsions. General form w/o emulsions. Lecithin & cholesterol form a monomolecular layer around the emulsion droplet instead of the typically multimolecular layers. Lecithin & cholesterol form a monomolecular layer around the emulsion droplet instead of the typically multimolecular layers. Cholesterol: a major constituent of wool alcohols & it gives lanolin the capacity to absorb water & form a w/o emulsion. Cholesterol: a major constituent of wool alcohols & it gives lanolin the capacity to absorb water & form a w/o emulsion.

39. Lecithin A phospholipid derived from egg yolk A phospholipid derived from egg yolk Produces o/w emulsions because of its strong hydrophilic character. Produces o/w emulsions because of its strong hydrophilic character. Animal derivatives are more likely to cause allergic reactions & are subject to microbial growth & rancidity. Animal derivatives are more likely to cause allergic reactions & are subject to microbial growth & rancidity. Advantage: ability to support formation of w/o emulsions. Advantage: ability to support formation of w/o emulsions.

40. Semi-synthetic Agents Stronger emulsifiers, nontoxic, & less subject to microbial growth. Stronger emulsifiers, nontoxic, & less subject to microbial growth. Synthetic hydrocolloids are the strongest emulsifiers, nontoxic, & not support microbial growth. Synthetic hydrocolloids are the strongest emulsifiers, nontoxic, & not support microbial growth. Cost may be prohibitive. Cost may be prohibitive. These synthetic agents are generally limited to use as o/w emulsifiers These synthetic agents are generally limited to use as o/w emulsifiers

41. Finely Dispersed Solid Particle Emulsifiers Finely Divided Solid Particle Emulsifiers Finely Divided Solid Particle Emulsifiers Form a particulate layer around dispersed particles. Form a particulate layer around dispersed particles. Most will swell in the dispersion medium to increase viscosity & reduce the interaction between dispersed droplets. Most will swell in the dispersion medium to increase viscosity & reduce the interaction between dispersed droplets.

42. Finely Dispersed Solid Particle Emulsifiers Most commonly they support the formation of o/w emulsions, but some may support w/o emulsions. Most commonly they support the formation of o/w emulsions, but some may support w/o emulsions. Include: bentonite, veegum, hectorite, Mg(OH)2, Al(OH)3 & Mg trisilicate. Include: bentonite, veegum, hectorite, Mg(OH)2, Al(OH)3 & Mg trisilicate.

43. Auxilarry Fatty acids: stearic acid, Fatty alcohols: stearyl or cetyl alcohol Fatty esters: glyceryl monostearate Serve to stabilize emulsions through their ability to thicken the emulsion. Have only weak emulsifying properties, always used in combination with other emulsifiers.

44. HLB System Hydrophile-lipophile Balance System Hydrophile-lipophile Balance System A system was developed to assist in making systemic decisions about the amounts & types of surfactants needed in stable products. A system was developed to assist in making systemic decisions about the amounts & types of surfactants needed in stable products. Has an arbitrary scale of 1 - 18. Has an arbitrary scale of 1 - 18. HLB numbers are experimentally determined for the different emulsifiers HLB numbers are experimentally determined for the different emulsifiers

45. HLB System If an emulsifier has a low HLB number, there is a low number of hydrophilic groups on the molecule and it will have more of a lipophilic character. If an emulsifier has a low HLB number, there is a low number of hydrophilic groups on the molecule and it will have more of a lipophilic character. Ex: Spans® generally have low HLB numbers & they are also oil soluble. They will cause the oil phase to predominate & form an w/o emulsion. Ex: Spans® generally have low HLB numbers & they are also oil soluble. They will cause the oil phase to predominate & form an w/o emulsion.

46. HLB System The higher HLB number would indicate that the emulsifier has a large number of hydrophilic groups on the molecule The higher HLB number would indicate that the emulsifier has a large number of hydrophilic groups on the molecule More hydrophilic in character. More hydrophilic in character. Tweens® have higher HLB numbers & also water soluble. Tweens® have higher HLB numbers & also water soluble. They will cause the water phase to predominate & form an o/w emulsion. They will cause the water phase to predominate & form an o/w emulsion. The higher HLB number would indicate that the emulsifier has a large number of hydrophilic groups on the molecule and therefore should be more hydrophilic in character. The Tweens ® have higher HLB numbers and they are also water soluble. Because of their water soluble character, Tweens ® will cause the water phase to predominate and form an o/w emulsion.

47. HLB System Combinations of emulsifiers can produce more stable emulsions than using a single emulsifier with the same HLB number. The HLB value of a combination of emulsifiers can be calculated as follows: Combinations of emulsifiers can produce more stable emulsions than using a single emulsifier with the same HLB number. The HLB value of a combination of emulsifiers can be calculated as follows:

48. Excercises What is the HLB value of a surfactant system composed of 20 g Span 20 (HLB = 8.6) + 5 g Tween 21 (HLB = 13.3)?

49. Methods of Emulsion Preparation Commercially, emulsions are prepared in large volume mixing tanks & refined & stabilized by passage through a colloid mill or homogenizer. Commercially, emulsions are prepared in large volume mixing tanks & refined & stabilized by passage through a colloid mill or homogenizer. Extemporaneous production is more concerned with small scale methods. Extemporaneous production is more concerned with small scale methods.

50. Methods of Emulsion Preparation Several methods are generally available to the pharmacist. Each method requires that energy be put into the system in some form. Several methods are generally available to the pharmacist. Each method requires that energy be put into the system in some form. The energy is supplied in a variety of ways: trituration, homogenization, agitation, & heat. The energy is supplied in a variety of ways: trituration, homogenization, agitation, & heat.

51. Continental Method Dry Gum, or 4:2:1 Method Dry Gum, or 4:2:1 Method Used to prepare the initial or primary emulsion from oil, water, & a hydrocolloid or "gum" type emulsifier (usually acacia). Used to prepare the initial or primary emulsion from oil, water, & a hydrocolloid or "gum" type emulsifier (usually acacia). The primary emulsion, or emulsion nucleus, is formed from 4:2:1 parts of oil:water:emulsifier. 4 parts oil & 1 part emulsifier represent their total amounts for the final emulsion. The primary emulsion, or emulsion nucleus, is formed from 4:2:1 parts of oil:water:emulsifier. 4 parts oil & 1 part emulsifier represent their total amounts for the final emulsion.

52. Continental Method In a mortar, the 1 part gum is levigated with the 4 parts oil until the powder is thoroughly wetted In a mortar, the 1 part gum is levigated with the 4 parts oil until the powder is thoroughly wetted 2 parts water are added all at once, & the mixture is vigorously continually triturated until the primary emulsion formed is creamy white & produces a "crackling" sound as it is triturated, usually 3-4 min 2 parts water are added all at once, & the mixture is vigorously continually triturated until the primary emulsion formed is creamy white & produces a "crackling" sound as it is triturated, usually 3-4 min

53. Continental Method Additional water or aqueous solutions may be incorporated after the primary emulsion is formed. Additional water or aqueous solutions may be incorporated after the primary emulsion is formed. Solid substances: active ingredients, preservatives, color, flavors. Generally dissolved & added as a solution to the primary emulsion. Solid substances: active ingredients, preservatives, color, flavors. Generally dissolved & added as a solution to the primary emulsion. Oil soluble substance: in small amounts, may be incorporated directly into the primary emulsion. Oil soluble substance: in small amounts, may be incorporated directly into the primary emulsion.

54. Continental Method Any substance which might reduce the physical stability of the emulsion, such as alcohol (which may precipitate the gum) should be added as near to the end of the process as possible to avoid breaking the emulsion. Any substance which might reduce the physical stability of the emulsion, such as alcohol (which may precipitate the gum) should be added as near to the end of the process as possible to avoid breaking the emulsion. When all agents have been incorporated, the emulsion should be transferred to a calibrated vessel, brought to final volume with water, then homogenized or blended to ensure uniform distribution of ingredients. When all agents have been incorporated, the emulsion should be transferred to a calibrated vessel, brought to final volume with water, then homogenized or blended to ensure uniform distribution of ingredients.

55. English (Wet Gum) Method Proportions of oil, water, & emulsifier are the same (4:2:1), but the order & techniques of mixing are different. Proportions of oil, water, & emulsifier are the same (4:2:1), but the order & techniques of mixing are different. The 1 part gum is triturated with 2 parts water to form a mucilage; then the 4 parts oil is added slowly, in portions, while triturating. The 1 part gum is triturated with 2 parts water to form a mucilage; then the 4 parts oil is added slowly, in portions, while triturating.

56. English (Wet Gum) Method After all the oil is added, the mixture is triturated for several min to form the primary emulsion. Then other ingredients may be added as in the continental method. After all the oil is added, the mixture is triturated for several min to form the primary emulsion. Then other ingredients may be added as in the continental method. It is more difficult to perform successfully, especially with more viscous oils, but may result in a more stable emulsion. It is more difficult to perform successfully, especially with more viscous oils, but may result in a more stable emulsion.

57. Bottle (Forbes) Method May be used to prepare emulsions of volatile oils, or oleaginous substances of very low viscosities. May be used to prepare emulsions of volatile oils, or oleaginous substances of very low viscosities. It is not suitable for very viscous oils since they cannot be sufficiently agitated in a bottle. It is not suitable for very viscous oils since they cannot be sufficiently agitated in a bottle. This method is a variation of the dry gum method. This method is a variation of the dry gum method.

58. Bottle (Forbes) Method One part powdered acacia (or other gum) is placed in a dry bottle & four parts oil are added. One part powdered acacia (or other gum) is placed in a dry bottle & four parts oil are added. The bottle is capped & thoroughly shaken. The bottle is capped & thoroughly shaken. The required volume of water is added all at once, the mixture is shaken thoroughly until the primary emulsion forms. The required volume of water is added all at once, the mixture is shaken thoroughly until the primary emulsion forms.

59. Bottle (Forbes) Method It is important to minimize the initial amount of time the gum and oil are mixed. The gum will tend to imbibe the oil, and will become more waterproof. It is important to minimize the initial amount of time the gum and oil are mixed. The gum will tend to imbibe the oil, and will become more waterproof.

60. Bottle (Forbes) Method It is also effective in preparing an olive oil & lime water emulsion, which is self-emulsifying. It is also effective in preparing an olive oil & lime water emulsion, which is self-emulsifying. In the case of lime water & olive oil, equal parts of lime water & olive oil are added to the bottle & shaken. No emulsifying agent is used, but one is formed "in situ" following a chemical interaction between the components. What emulsifying agent is formed? In the case of lime water & olive oil, equal parts of lime water & olive oil are added to the bottle & shaken. No emulsifying agent is used, but one is formed "in situ" following a chemical interaction between the components. What emulsifying agent is formed?

61. Beaker Method When synthetic or non-gum emulsifiers are used, the proportions given in the previous methods become meaningless. When synthetic or non-gum emulsifiers are used, the proportions given in the previous methods become meaningless. Most appropriate method for preparing emulsions from surfactants or other non-gum emulsifiers is to begin by dividing components into water soluble & oil soluble components Most appropriate method for preparing emulsions from surfactants or other non-gum emulsifiers is to begin by dividing components into water soluble & oil soluble components

62. Beaker Method All oil soluble components are dissolved in the oily phase in one beaker & all water soluble components are dissolved in the water in a separate beaker. All oil soluble components are dissolved in the oily phase in one beaker & all water soluble components are dissolved in the water in a separate beaker. Oleaginous components are melted & both phases are heated to ±70°C over a water bath. Oleaginous components are melted & both phases are heated to ±70°C over a water bath.

63. Beaker Method The internal phase is then added to the external phase with stirring until reaches room temperature. The internal phase is then added to the external phase with stirring until reaches room temperature. The mixing of such emulsions can be carried out in a beaker, mortar, or blender; or, in the case of creams & ointments, in the jar in which they will be dispensed. The mixing of such emulsions can be carried out in a beaker, mortar, or blender; or, in the case of creams & ointments, in the jar in which they will be dispensed.

64. Auxiliary Methods Instead of, or in addition to, any of the preceding methods, the pharmacist can usually prepare an excellent emulsion using an electric mixer or blender. Instead of, or in addition to, any of the preceding methods, the pharmacist can usually prepare an excellent emulsion using an electric mixer or blender.

65. Auxiliary Methods An emulsion prepared by other methods can also usually be improved by passing it through a hand homogenizer, which forces the emulsion through a very small orifice, reducing the dispersed droplet size to about 5 µm or less. An emulsion prepared by other methods can also usually be improved by passing it through a hand homogenizer, which forces the emulsion through a very small orifice, reducing the dispersed droplet size to about 5 µm or less.

66. HLB Values Commercial NameChemical NameHLB Value PEG 400 MonolauratePolyoxyethylene monolaurate13.1 Sodium lauryl SO4 40 Span® 20Sorbitan monolaurate8.6 Span® 60Sorbitan monostearate4.7 Span® 85Sorbitan trioleate1.8 TEA oleate 12 Tween® 20 Polyoxyethylene sorbitan monolaurate 16.7 Tween® 65Polyoxyethylene sorbitan tristearate 10.5