Term
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Definition
| one part dispersed in another part. |
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Term
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Definition
| Solids-solid, liq-solid, solid-liq, gas-liq |
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Term
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Definition
| to collect (a gas, liquid, or dissolved substance) in condensed form on a surface |
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Term
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Definition
| can be gas-liq (liquid aerosol) or gas-solid (solid aerosol). but not gas-gas because all gases are soluble |
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Term
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Definition
| liq-gas (foam), liq-liq (emulsion), liq-solid (solid) |
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Term
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Definition
| sol-gas (solid foam), sol-liq (gel), sol-sol. |
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Term
| disperse systems classes: molecule |
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Definition
| size: < 1nm. ex: oxygen molecules |
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Term
| disperse systems classes: colloidal & disperson |
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Definition
| .5um to 1.0 um. ex: colloidal Ag sols, milk |
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Term
| disperse systems classes: coarse dispersion suspensions |
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Definition
| size: >.5 um. RBC, pharmaceutical emulsions. |
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Term
| kinetic properties of colloids: |
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Definition
| brownian motion, duffusion, osmotic pressure, sedimentation, viscostiy. |
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Term
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Definition
| model fo movement of a particle that is under the influence of random or stochastic mechanism. ex: diffusion, brownian motion |
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Term
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Definition
| erratic motion observed with particles up to 5um. bombardment of the particles of the dispersion medium is responsible for the broanian motion. velocity of the particle increases with decrease particle size. |
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Term
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Definition
| particle diffuse spontaneously from a region of higher concentratino to one of lower concentration until the concentration of the system is uniform through out. direct result of brownian movement. |
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Term
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Definition
| when particles can't diffuse through the system because of the presence of a semi-permeable membrane, the solvent molecule will move from the lower concentration of the solute to the higher concentration: II = cRT |
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Term
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Definition
diffusion: movement of solute together with solvent.
osmosis: movement of solvent molecules |
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Term
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Definition
| important factor of disperse systems. it is possible to manipulate the density of the dispersion medium by adding nonionic substances. |
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Term
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Definition
rheo = flow. logos = science.
rheology describes the flow of liquids and the deformation of solids. involved in: mixing, flow of materials, packaging into containers, removal prior to use. |
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Term
| classification of materials according to the types of flow: |
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Definition
| newtonian systems (water, ethanol, benzene)(measured in poise) or non-newtonian systems (colloidal solutions, emulsions, suspensions, ointments) |
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Term
| 3 classes of non-newtonian flow |
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Definition
| plastic, pseudoplastic, dilatant |
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Term
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Definition
| presence of yield value. associated with the presence of flocculated particles in concentrated suspensions. more flocculated, the higher the yield value |
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Term
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Definition
| natural and synthetic gums. ex: methylcellulose, sodium alginate. aka the shear-thinning systems. are polymers in solution |
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Term
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Definition
certain suspensions with a high percentage of dispersed solids exhibit an increase in the resistance to flow with increasing rates of shear.
dilatant = increase volume. aka shear-thickening systems. high concentration of small, deflocculated particles. |
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Term
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Definition
| the magnitude of the force acting perpendicular to the unit length of a line in the surface. in gamma. the tension that exists between a liquid and the atmosphere in known as the surface tension. the tension that exists at the interface between two immiscible liquids is known as the interface tension. |
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Term
| factors that affect surface tension |
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Definition
| 1. increase temp (decrease surface tension) 2. add surface active agents (decrease surface tension) |
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Term
| surface-actice agents, aka surfactants |
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Definition
| molecule that preferentially absorb at an interface (see: solid/liquie froth flotation, liq/gas foams, or liq/liq emulsions). significantly alter interfacial free energy (work needed to create or expand interface/unit area). surface free energy of interface minimized by reducing interfacial area. amphiphillic nature- adsorb at interfaces. |
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Term
| surface active agent aggregation |
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Definition
| increase concentration = aggregation occurs. the aggregates are called "micelles" when it contains 50 or more monomers. the concentration at which micelles form is called CRITCAL MICELLE CONCENTRATION (CMC). surface tension decreases and then remains constant after CMC. |
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Term
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Definition
| below CMC only unimers are present. above CMC there are micelles in equilibrium with unimers. |
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Term
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Definition
| amphipathic. tail is hydrophobic (little affinity for bulk solvent. usually hydrocarbon chain. linear or branched) head is hydrophilic (strong affinity for bulk solvent. can be neutral or charged). |
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Term
| various supramolecule aggregates |
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Definition
| unimers, spherical, cylindrical, bilayer lamella, reverse micelles, inverted hexagonal. form in this order and water content decreases |
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Term
| hydrophilic-lyophilic balance |
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Definition
| the HLB of a surfactant reflects its partitioning behavior between a polar (water) and nonpolar (oil) medium. strongly hydrophilic: HLB --> 40. strongly lyophilic surfactant: HLB --> 1. HLB dependant upon characteristics of polar and nonpolar groups. |
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Term
| 3 classifications of sruface active agents |
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Definition
| anionic, cationic, nonionic. based on HLB values and uses. depending on the number and nature of the polar and nonpolar groups present, the amphiphile may be predominantly hydrophillic or lipophillic or reasonably well balanced. |
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Term
| HLB scale and classification |
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Definition
| 1-3 = most antifoaming agents. 3-6 = w/o emulsifying afents. 7-9 = wetting and spreading agents. 8-16 = o/w emulsifying agents. 13-15 = detergents. 16-18 solublizing agent. |
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Term
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Definition
| consists of particulate matter (dispersed phase) distributed through a continuous or dispersion medium. classification based on size: molecular dispersion, colloidal dispersions, and coarse dispersions. |
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Term
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Definition
| less that 1.0 nm. ex: oxygen molecules, glucose, ordinary ions. particles invisible to microscope, undergo rapid diffusion. pass thru ultrafilter and semipermeable membrane. |
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Term
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Definition
| 1.0 nm to .5 um. ex: colloidal silver sols, natural and synthetic polymers, sponge cake, fog, butterfly wings. particles visible in electron microscope. do not pass semipermeable membrane, diffuse very slowly. |
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Term
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Definition
| greater than .5 um. ex: grains of sand, emulsions, suspensions, RBC. visible under microscope. do not dialize thru semipermeable membrane. particles do not diffuse. |
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Term
| application of colloids: hydrogels and micorparticles |
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Definition
| liposomes, micelles, nanoparticles, nanocrystals, hydrogels (wound healing, tissue angering, sustained-release delivery) and microparticles (carriers for vaccines and anticancer drugs, target drug delivery, improve immunization by mucosal administration) |
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Term
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Definition
| microscopic spherical vesicles that form when phospholipids are hydrated. arrange themselves in cheets (heads up and tails down). sheets join tail to tail to form bilayer membrane. have been evaluated as delivery system for drugs, vitamins, and cosmetic materials. |
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Term
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Definition
| partiles of one susbtance are spread out, or dispersed, in another susbtance. spread-out partivles are in small clumps which are bigger than a solution but smaller than a suspension. |
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Term
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Definition
| process where solvent and other small molecules can pass thru a membrane. similar to osmosis but the holes in the membrane are larger. even hydrated ions can pass thru. in hemodialysis an isotonic solution is used to prevent loss of important electrolytes and glucose |
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Term
| type of colloidal systems |
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Definition
lyophilic: colloidal particles interact with dispersion medium simply by dissolving the material in solvents lyophobic: colloid particle has little attraction for the dispersed medium. meed special methors to prepare (dispersion of condensation method)
association: amphiphilic molecules (surfactants) aggregate to form supermolecular structure |
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Term
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Definition
| solvent loving, owing to their affinity for the dipsersion medium, such materials form colloidal dispersions. can be hydrophilic (acacia or gelatin) or lipophilic (rubber or polystyrene). |
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Term
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Definition
| little attraction for solvents (solvent hating). generally composed of inorganic particles dispersed in water. necessary to use special methods to prepare. ex: gold, silver, sulfur. |
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Term
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Definition
| dispersion methods (core particles are reduced in size of colloids). condensation methods (are cuased to aggregate into particles of colloidal size range). ultrasonic generators (frequencies in excess of 20,000). productin of an electrical arc. vapor condensation (forms colloids). and milling and grinding (mills are less efficient) |
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Term
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Definition
| referred to as association colloids since they are aggregates of surfactant molecules and are colloidal in size. upon addition of surfactant to water, the overall concentration rises until 2 limits are reached: maximum solubility fo the monomer in water and saturation of the interface. can self assemble to shield hydrophobic parts |
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Term
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Definition
| if concentration is sufficiently high, surfactants can form aggregates in aqueous solution (ie: micelles). typically spheroidal particles of 2.5-6 nm in diameter. onset of micellization observed by sudden change in measured properties of solution at characteristic surfactatnt concentration, ie CMC |
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Term
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Definition
| when a strong beam of light is passed through a colloidal sol, a visible cone resulting from scattering by the colloidal particles, is formed. can determine the molecular weight. obtain info on the diffusion coefficient, shape and size of colloidal particles. |
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Term
| kinetics-diffusion 3 main rules |
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Definition
1. the velocity of molecules increases with decreasing particle size.
2. the velocity of the molecules increases with increasing temp
3. the velocity of molecules decrease with increasing of the medium viscosity. |
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Term
| stability of colloid systems |
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Definition
| thermodynamicall unstable. stabilized only by the presence of electric charges (a small amount of electrolyte). a large amount of electrolytes leads to coagulation and sedimentation |
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Term
| sedimentation and solubility |
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Definition
sedimentation may result in "salting out" with sufficient salt. from highest to lowest precipitation power: citrate, tartrate, sulfate, acetate, cloride, nitrate, bromide, iodide.
alcohol and acetone can decrease the solubility of hydrophilic sol |
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Term
| stable system--phase seperation: 2 ways |
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Definition
1. stable to flocculation to coagulation to sedimentation to phase seperationg.
2. stable to sedimentation to flocculation to coagulation to phase separation. |
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Term
| pharmaceutical important of emulsions |
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Definition
| lipid emulsions provide an alternative formulation form for the following drugs: sparingly soluble, hydorgphic, and iolizable drugs. |
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Term
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Definition
| provides a solubilized drug for oral, parenteral and intraarticular administration. enhances drug absorption and bioavailability, increase therapeutic efficacy, eliminate adverse injection site reactions, clinically accepted and successfully marketed. |
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Term
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Definition
| conventional prep for iv administration in non-aqeous solvent cause pain on injection and thrombophlebitis. diazepam emulsion, no pain or thrombophlebitis is experienced |
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Term
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Definition
| anti-tumor agents. indicated for ovarian, breast, and non0small cell lung cancer. difficultly in formulating i.v. dosage form due to poor aqeuous solibility. causes allergic reaction upon injection. precipitation on aqeous dilution |
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Term
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Definition
| a thermodynamicall unstable system consisting of at least 2 immiscible liquid phases, one of which is dispersed as globules (dispersed phase) in the other liquid phase (continuous phase). stabilized by presence of an emulsifying agent. either phase may range in consistency from a mobile liquid to semisolid. thus, emulsified systems range from lotions to ointments and creams. |
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Term
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Definition
| shear rates are necessary for dispersion of the internal phase into fine droplets. the shear forces are opposed by forces operating to resis distortion and subsequent breakup of the droplet. surfacactants help greatly by lowering interfacial tension, the primary reversible component resisting droplet distortion. they also may play an important role in determining whether and oil-in-water (o/w) or water-in-oil (w/o) emulsion |
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Term
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Definition
| O/W. when the oil phase is dispersed as globules throughout an aqeous continuous phase, the system is refered to as o/w. medicinal emulsions for oral administration of water-insoluble liquids.. require use of an o/w emulsifying agent. (acacia, gelating) |
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Term
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Definition
| w/o. when the oil phase serves as the continuous phase, the emulsion is spoken of as a w/o product. used almost exclusively for external application. |
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Term
| methods of analysis: Dye method |
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Definition
| water-soluble dye is dusted on the surface of the emulsion. if water is external phase (ie: o/w) dye will dissolved. if w/o particles of dye will be clumped. |
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Term
| methods of analysis: dilution of continuous medium |
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Definition
| if emulsion mixes freely with the water, it is of the o/w type |
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Term
| methods of analysis: electrical conductance method |
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Definition
| a current will pass through the emulsion and can be made to deflect a voltemeter or cause light in o/w where external phase is water. if oil is continuous phase, the emulsiong fails to carry the current. |
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Term
| i.v. pharmaceutical applications of emulsion |
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Definition
| when the emulsion is administered intravenously, the droplets are normally rapidly taken up by the wells the reticuloendothelial system (macrophages of theliver). rate of clearance by the macrophages increases as the droplet size becomes larger, or the surface area charge (+ or -) increases. |
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Term
| theories of emulsification |
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Definition
| it should be capable of explaining: the stability of the product and the type of emulsion formed. |
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Term
| cohesive and adhesive forces in emulsification |
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Definition
failure of 2 immiscible liquids to remain mixed is explained by the cohesive force betwen the molecules of each spearate liquid is greater than the adhesive force between the two liquids.
when one liquid is broken into small particles, the interfacial area of the globules consistitutes a surface that is enormous compared with the surface area of the original liquid. |
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Term
| 3 groups of emulsifying agents |
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Definition
1. surface active agents - are adsorbed at oil-water interfaces to form monomolecular films and reduce interfacial tension
2- hydrophillic colloids- form multi-molucelar film around the dispersed droplets of oil in an o/w emulsion.
3. finely divided solid particles - are adsorbed at the interface between two immiscible liquid phases and form a film of particles around the dispersed globules. the common factor is formation of a film (monomolecular, multi-molecular, or particulate) |
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Term
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Definition
| surface-active agents, or amphiphiles, reduce interfacial tension because of their adsorption at the oil-water interface to form monomolecular films. significance is the fact that the dispersed droplets are surrounded by a coherent monolayer that helps to prevent coalescence between two droplets as they approach one another. also promting stability is the presence of a surface charge, which will cause repulsion between adjacent particles. |
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Term
| multi-molecular adsorption and film formation |
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Definition
| hydrated lyophilic colloids have been used for many years as emulsifying agents. they differ from the synthetic surface-active ageents in that 1. they do not cause appreciable lowering of interfacial tension and 2. they form a multi rather than monomolecular film at the interface |
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Term
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Definition
| the type of emulsion that is produced (o/w or w/o) depends primarily on the property of the emulsifyin agent. HLB is referred to as the poar non-polar nature of the emulsifier. In general, o/w emulsions are formed when the HLB of the emulsifier is within the range of about 9 to 12. w/o is 3 to 6. |
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Term
| physical stability of emulsion |
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Definition
| in the light of these considerations, the instability of pharmaceutical emulsions may be classified: floc and creaming, coalexcence and breaking, miscellaneous physical and chemical changes, phase inversion |
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Term
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Definition
| they appear as clear transparent solutions. may not be thermodynamically stable. somewhere between thermodynamically stable solubilized solutions and ordinary emulsions (unstable). droplets of oil in water or droplets of water in oil. |
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Term
| micor-emulsion formulation |
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Definition
| emulsifying adjunct or co-surfactant is used in prep of microemulsions. the surfactant and co-surfactant molecules form an adsorbed film on the micro-emulsion particles to prevent coalescence. |
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