Methods of Emulsification

In aU methods there is Hquid flow with unbounded and strongly confined flow. In the unbounded flow, any droplets are surrounded by a large amount of flowing liquid (the confining walls of the apparatus are far away from most droplets), while the forces can be either frictional (mostly viscous) or inertial. Viscous forces cause shear stresses to act on the interface between the droplets and the continuous phase (primarily in the direction of the interface). The shear stresses can be generated by either laminar flow (LV) or turbulent flow (TV) this depends on the Reynolds number R,  

For laminar flow R 1000, whereas for turbulent flow Rg 2000. Thus, whether the regime is linear or turbulent depends on the scale of the apparatus, the flow rate, and the liquid viscosity [9-12]. 

If the turbulent eddies are much larger than the droplets they exert shear stresses on the droplets however, if the turbulent eddies are much smaller than the droplets then inertial forces will cause disruption (turbulent/inertial). 

In bounded flow other relationships hold for example, if the smallest dimension of the part of the apparatus in which the droplets are disrapted (e.g., a slit) is comparable to the droplet size, the flow will always be laminar. A different regime prevails, however, if the droplets are injected directly through a narrow capillary into the continuous phase (injection regime), namely membrane emulsification. 

Within each regime, one essential variable is the intensity of the forces which are acting the viscous stress during laminar flow Cyiseous is given by. 

A different regime prevails if the droplets are directly injected through a narrow capillary into the continuous phase (injection regime), e.g. membrane emulsification. 

The intensity in turbulent flow [9, 10] is expressed by the power density s (the amount of energy dissipated per unit volume per unit time (for laminar flow = rjG ). 

The most important regimes are laminar/viscous (LV), turbulent/viscous (TV) and turbulent/inertial (TI). 

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Prepare a liposome suspension, containing MPB—PE, at a total lipid concentration of 5 mg/ml in 0.05 M sodium phosphate, 0.15 M NaCl, pH 7.2. Activation of DPPE with SMPB is described in Section 2. A suggested lipid composition for vesicle formation is PC cholesterol PG MPB—PE mixed at a molar ratio of 8 10 1 1. The presence of relatively high levels of cholesterol in the liposomal recipe dramatically enhances the conjugation efficiency of the component MPB—PE groups (Martin et al., 1990). Any method of emulsification to create liposomes of the desired size and morphology may be used (Section 1). 

Quasi-elastic light scattering is an excellent technique for studying the formation and stability of submicrometer emulsions. Improvements in the methods of quasi-elastic light scattering data acquisition and analysis that enable full particle-size distribution studies of sub-micrometer emulsion systems are discussed. Using several oil/water emulsion systems as examples, we demonstrate the ability of these techniques to determine the effect of emulsifier concentration on the particle-size distribution produced by an inversion method of emulsification. Some of the benefits of obtaining the full distribution are also discussed. 

Influence of the Method of Emulsification. Miniemulsions prepared by the second method are more stable than those prepared with the preemulsification method. 

The Table IV gives 2 examples of the influence of the method of emulsification on the stability of miniemulsions prepared with the same amounts of lipopeptide (LP) and cetyl alcohol (C15OH). When the oil is styrene the stability of the miniemulsion increases from 60 to 240 days. When the oil is vaseline oil, the stability of the miniemulsion increases from 20 to 70 days. 

The emulsification of the monomer is not usually of primary importance in emulsion polymerization, although it has been shown (Ugelstad et al., 1973 Ugelstad and Hansen, 1979) that if the size of the emulsion droi ets ran, by the use of special methods of emulsification, be reduced considerably below that which would normally be attained, the emulsion... 

The difficulty of obtaining ready access of alkali to the mass of fats in soap manufacture has led to the introduction of various methods of emulsification reaction. Among these mention must be made of the Monsavon process. In this the chemical reaction is accelerated by passing the mixture of fats and alkali through a colloid mill the homogenized solution is subsequently heated to 100°C. to start the hydrolysis. The soap produced in this way contains a little free alkali, usually of the order 0.2%. 

Traditional methods of emulsification include high-pressure homogenizers, rotor-stator systems, and ultrasound homogenizers [110, 111], The first two examples employ high mechanical shear rates to produce small droplets of the... 

Many studies have been reported about the methods of emulsification of hydrocarbons, such as emulsification by surface-active agents, by mechanical agitation, or by biological methods. For the most favorable configurations between oil droplets and cells for growth, the biologically active emulsion of hydrocarbon was proposed. Munk (1969) indicated that the larger the amount of lipid a cell contained, the faster it incorporated hydrocarbon. Mimura et al. (1970) studied the characteristic phenomena of emulsification in hydrocarbon fermentation, and... 

With any given pair of immiscible liquids, two types of emulsions are possible. One is that in which water is the external, and oil, the inteimal phase, known as oil-in-water emulsion, or water outside emulsion (o/w). The other type, with oil as external, and water as the internal phase, is known as water-in-oil emulsion, or oil outside emulsion (W/O). If an emulsion contains 50% water or other aqueous solution, and 50% oil or oil-like substance, it is possible to produce an o/w or a W/O emulsion, which will show the same percent composition but, nevertheless, be two entirely different emulsions. This all depends on the method of emulsification, the emulsifying agent, the soluble materials in the water phase, and the fineness of particles. 

In this technique, a transition in the affinity is obtained by changing the water volume fraction, instead of changing the temperature. By successively adding water into oil, initially water droplets are formed in a continuous oil phase. Increasing the water volume fraction changes the spontaneous curvature of the surfactant from initially stabilizing a w/o microemulsion to an o/w microemulsion at the inversion locus. This transition is referred to as PIC. PIC method of emulsification involves... 

The linewidths of P-NMR can be used to character ize the motional properties of phospholipids. In emul sions, the linewidths are affected by the aqueous phase pH, size of dispersion states of particles, and methods of emulsification. The hydrophilic head-group motions of emulsified egg-yolk PC and lyso PC are examined by P-NMR to evaluate their phospholipid states and stability. The results suggest that the head-group motions of phospholipids are related to emulsion sta bility (68, 69). 

TABLE 11.1. Some Typical Mechanical Methods of Emulsification... 

In later experiments (14), these microscopic particles were separated and measured, and their formation in monodisperse polystyrene latexes was studied as a function of the method of emulsification in all cases, their weight percent was small. 

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