Emulsions phase separation

Microspheres were prepared from carboxymethyl chitosan and alginate by emulsion phase separation. The encapsulated bovine serum albumin was... 

Hollow and porous polymer capsules of micrometer size have been fabricated by using emulsion polymerization or through interfacial polymerization strategies [79,83-84, 88-90], Micron-size, hollow cross-linked polymer capsules were prepared by suspension polymerization of emulsion droplets with polystyrene dissolved in an aqueous solution of poly(vinyl alcohol) [88], while latex capsules with a multihollow structure were processed by seeded emulsion polymerization [89], Ceramic hollow capsules have also been prepared by emulsion/phase-separation procedures [14,91-96] For example, hollow silica capsules with diameters of 1-100 micrometers were obtained by interfacial reactions conducted in oil/water emulsions [91],... 

Figure 8. Preparation mechanisms of PLGA nanospheres by the emulsion-phase separation method in an oil system.

Emulsions Phase separation, pH, viscosity, microbial bioburden, mean size and distribution of dispersed globules. 

Emulsion phase separation. Water-soluble drugs are fabricated in the form of microcapsules by this method. An aqueous phase containing dissolved drug and an organic phase containing polymer are emulsified. Then polymer is phase separated using the techniques such as temperature change, addition of salts, etc. A nonsolvent then is used to harden the microspheres. 

BSA-loaded microspheres prepared from carboxy methylated chitosan and alginate with emulsion phase separation and cross-linked with Ca ions... 

Gas sampling probe, shown in Fig. 30c, applied to sample gas from bubble and emulsion phases separately. Reactor 0.1 m i.d. 0.7 m FBC bed material sand, fuel coal... 

Capron, L, Costeux, S. Eljabourov, M. (2001).Water in Water Emulsions Phase Separation and Rheology of Biopolymer Solutions. Rheol. Acta, 40,441-456. 

Capron I, Costeux S, Djabourov M. 2001. Water in water emulsions Phase separation and rheology of biopolymer solutions. Rheolog Acta 40 441-456. 

Capron, I., Costeux, S., and Djabourov, M. 2001. Water in water emulsion Phase separation and rheology in biopolymer solutions. Rheol. Acta 40 441 56. 

If two pure, immiscible liquids, such as benzene and water, are vigorously shaken together, they will form a dispersion, but it is doubtful that one phase or the other will be uniquely continuous or dispersed. On stopping the agitation, phase separation occurs so quickly that it is questionable whether the term emulsion really should be applied to the system. A surfactant component is generally needed to obtain a stable or reasonably stable emulsion. Thus, if a little soap is added to the benzene-water system, the result on shaking is a true emulsion that separates out only very slowly. Theories of... 

Solvent Extraction. Solvent extraction has widespread appHcation for uranium recovery from ores. In contrast to ion exchange, which is a batch process, solvent extraction can be operated in a continuous countercurrent-fiow manner. However, solvent extraction has a large disadvantage, owing to incomplete phase separation because of solubihty and the formation of emulsions. These effects, as well as solvent losses, result in financial losses and a potential pollution problem inherent in the disposal of spent leach solutions. For leach solutions with a concentration greater than 1 g U/L, solvent extraction is preferred. For low grade solutions with <1 g U/L and carbonate leach solutions, ion exchange is preferred (23). Solvent extraction has not proven economically useful for carbonate solutions. 

Emulsification is essential for the development of all types of skin- and hair-care preparations and a variety of makeup products. Emulsions (qv) are fine dispersions of one Hquid or semisoHd ia a second Hquid (the contiauous phase) with which the first substance is not miscible. Generally, one of the phases is water and the other phase is an oily substance oil-ia-water emulsions are identified as o/w water-ia-oil emulsions as w/o. When oil and water are mixed by shaking or stirring ia the absence of a surface-active agent, the two phases separate rapidly to minimize the iaterfacial energy. Maintenance of the dispersion of small droplets of the internal phase, a requirement for emulsification, is practical only by including at least one surface-active emulsifier ia the oil-and-water blend. 

The stability of an emulsion mud is an important factor that has to be closely monitored while drilling. Poor stability results in coalescence of the dispersed phase, and the emulsion will separate into two distinct layers. Presence of oil in the emulsion mud filtrate is an indication of emulsion instability. 

The initial HC1 wash results in an emulsion and up to 2 hr may be required for phase separation. At that point, any remaining emulsion should be separated and added to 100 mL of chloroform and 100 mL of LON HC1 solution. The chloroform layer is then combined with the other organic phases. 

Chloropromazine (8—34 wt% loading) has been microencapsulated in PCL-cellulose propionate blends by the emulsion solvent evaporation method (61). Phase separation for some ratios of the two polymers was detectable by SEM. The release rate from microcapsules in the size range of 180-250 pm in vitro (Fig. 11) was directly proportional to the PCL content of the blend, the half-life (50% drug release)... 

Monflier et al. (1997) have suggested Pd catalysed hydrocarboxylation of higher alpha olefins in which chemically modified P-cyclodextrin (especially dimethyl P-cyclodextrin) is u.sed in water in preference to a co-solvent like methanol, acetone, acetic acid, acetonitrile, etc. Here, quantitative recycling of the aqueous phase is possible due to easy phase separation without emulsions. A similar strategy has been adopted by Monflier et al. (1998) for biphasic hydrogenations for water-in.soluble aldehydes like undecenal using a water-soluble Ru/triphenylphosphine trisulphonate complex with a. suitably modified p-cyclodextrin. 

An important problem in emulsified organic-aqueous systems is that of scale-up, which is concerned with the realization of stable emulsions and the separation of phases after the reaction. The use of biphasic membrane systems that contain the enzyme and keep the two phases separated is likely to solve this problem. In the case of 5-naproxen an ee of 92% has been demonstrated without any decay in activity over a period of two weeks of continuous operation. A number of examples of biocatalytic membrane reactors have been provided by Giorno and Drioli (2000) and include the conversion of fumaric acid to L-aspartic acid, L-aspartic acid to L-alanine, and cortexolone to hydrocortisone and prednisolone. 

Drain the aqueous acetonitrile (lower) phase into a 500-mL round-bottom flask, and save the separatory funnel for extraction. Extract the hexane-fat mixture by transferring the mixture back to the polypropylene centrifuge bottle and adding 100 mL of acetonitrile-water (4 1, v/v) solution. Balance the duplicate centrifuge bottles, and cap and shake the bottles for 10 min on the shaker. Centrifuge the second extract at 11 000 rpm for 15 min. Decant this second extract into the 250-mL separatory funnel as before. After phase separation, combine the aqueous extracts in the 500-mL round-bottom flask, and discard the top hexane-fat layer. Add 10 drops of Dow Coming Antifoam B emulsion and 3 mL of 10% aqueous Igepal CO-660 (nonionic surfactant) to the flask. 

After heating at 40° C, liquid anhydrous milk fat (1 v) and the different protein solutions (10 v) were premixed using a polytron (PT 3000, Kinematica) and emulsified with a homogenizer (ALMO, Legrand, France) at about 40°C in order to obtain oil-in-water emulsions. After separation from the aqueous phase by centrifugation for 5 min at lOOOg, milk fat droplets stabilized by different proteins were washed twice with a phos-... 

Changes in the natures of individual phases of or phase separation within a formulation are reasons to discontinue use of a product. Phase separation may result from emulsion breakage, clearly an acute instability. More often it appears more subtly as bleeding—the formation of visible droplets of an emulsion s internal phase in the continuum of the semisolid. This problem is the result of slow rearrangement and contraction of internal structure. Eventually, here and there, globules of what is often clear liquid internal phase are squeezed out of the matrix. Warm storage temperatures can induce or accelerate structural crenulation such as this thus,... 

The viscosity of an emulsion can be of crucial importance for its stability, especially the viscosity of the external phase. A high viscosity reduces creaming and also lessens the tendency of particles to coalescence and produce phase separation. Examples of the widely used viscosity-imparting agents are alginates, bentonite, carboxymethylcellulose, polyvinyl pyrrolidone, hydroxypropylcellulose, and carbomer. 

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