Emulsification solvent extraction

Other recent applications of emulsion formulation involve mucosal gene and vaccine delivery [185-187] and the preparation of polymeric microspheres by the w/o emulsification solvent extraction technique [188],... 

Yeh MK, Coombes AG, Jenkins PG, Davis SS. A novel emulsification-solvent extraction technique for production of protein loaded biodegradable microparticles for vaccine and drug delivery. Journal of Controlled Release. 1995 33 437-445. 

Figure 11.1 Schematic of water-inoil-in-water (W1/OAV2) emulsification solvent extraction/ evaporation method.

State compared to in the dissolved state [58]. Properties of the drug such as its hydro-phihcity or hydrophobicity and whether it is easily denatured are usually key determinants of which emulsification solvent extraction/evaporation method to use for a particular drug. 

The porosity (ie, pore size and amount of pores) of microparticles is also an important characteristic to take into consideration when fabricating microparticles because it plays an essential role in controlling the release of payloads. The porosity and morphology of particles are usually determined by scanning electron microscopy (SEM). For the emulsification solvent extraction/evaporation method of fabrication, the rate of solvent extraction, which depends on the flow in the stirred vessel the droplet size the temperature and the dispersed phase hold-up in the 0/W emulsion have an effect on porosity [87]. The porosity usually increases with a decrease in solvent extraction rate. The porosity of microparticles results in initial burst release due to pore diffusion [78,88]. Mao et al. studied the influence of different W/O/W emulsification solvent extraction/evaporation process parameters on internal and external porosity of PLGA microparticles [78]. The surface morphology of the microparticles can be influenced by the type of polymer, internal aqueous phase voliune (Wi), volume of continuous phase (W2), polymer concentration, homogenization speed, and equipment used for the primary emulsion [78,79]. 

The solvent extraction of chlorinated pesticide residues from soil is often achieved by using mixtures of solvents such as hexane-isopropanol or hexane acetone, but can be unsatisfactory owing to the emulsification problems [2, 3] or, with hexane-isopropanol, poor recovery [2, 4], Acetone extraction of soil is efficient [4, 5] but problems can arise from large amounts of coextracted material unless an efficient clean-up technique [6] is used prior to analysis by gas chromatography. 

The number average diameter of microspheres obtained from polymers synthesized, by emulsification of polymer solutions followed by solvent extraction and/or solvent evaporation methods, can be controlled by choosing the appropriate conditions at which particles are produced. However, by this method particles with 15 p,m and with D D > 1.9 are produced. Spray drying did not provide poly(L-Lc) particles with regular spherical shape. Direct synthesis of poly(L-Lc) microspheres by ring-opening polymerization with stepwise monomer addition can be used as a method of choice for the production of microspheres with diameters controlled to ca. 6 p.m and with diameter polydispersity parameter < 1.20. 

In addition to the above, it is predicted that impinging streams can also be used for some other processes, such as solvent extraction, emulsification etc., to yield good performances. 

Solvent extraction Podbielniak extraction Membrane solvent extraction Coupled transport Minimum emulsification and associated entrainment loss Enhanced selectivity and concentration... 

The pharmaceutical field is among those most widely exploiting ultrasonic emulsification (mainly for the preparation of emulsion-based drugs). Thus, US emulsification has been recently used to prepare biodegradable nanoparticles that can in turn be used to obtain drug-loaded biodegradable microspheres. The method involves ultrasonic emulsification in a continuous flow system to obtain suspended nanoparticles, followed by collection of the particles, solvent extraction and evaporation [49]. 

Increasing levels of emulsification significantly depleted protein from the fat globule in the mix. The adsorbed protein content in the mix (mg m of fat surface area) correlated with major characteristic analyses describing the fat structure in ice cream (fat agglomerate size, fat agglomeration index, solvent extractable fat Fig. 6). Thus, the measurement of protein load in the mix can be used to predict ice-cream-fat stability and related structure. Structural analyses indicated enhanced interaction between fat and air as protein adsorption decreased. It was also observed that the fat content in the dripped portion collected from a meltdown test correlated well with other indices of fat destabilization. 

The ioxilan carbonate particles were prepared as a contrast medium by solvent extract/ evaporation method. The preparation involved emulsification of a methylene chloride solution of the carbonate, removal of solvent, and washing and sizing the particles. The iodine content of the particles was 45%. The average diameter of the ioxilan carbonate particles was 1.1 pm, 95%of them ranging from 0.6 and 2.0 jam. Electron microscopy showed the particle surface to be smooth, and the particles showed practically no aggregation when mixed with rat plasma. The LDgo value for the ioxilan carbonate particles was 1.4 g I/kg for... 

Immiscible-liquid solvent extraction is a well-established practice for recovery, concentration, and purification of organophilic solutes (e.g., antibiotics, amino acids, vitamins) present in aqueous process streams such as fermentation broths or plant or animal tissue extracts [88]. The process is, however, frequently rendered difficult or impossible by problems of emulsification, loss of entrained solvent, and contamination by particulate impurities in the feed. Integrated membrane separation with liquid/liquid extraction is iUustrated in Fig. 9.7. 

The tendency toward Pu(IV) polymerization is of considerable practical importance in process operations involving plutonium solutions. Dilution of an acidic plutonium solution with water can result in polymerization in localized regions of low acidity, so plutonium solutions should be diluted instead vdth acid solutions. Polymerization can result from leaks of steam or water into plutonium solutions or by overheating during evaporation. Polymer formation can clog transfer lines, interfere with ion-exchange separations, cause emulsification in solvent extraction and excessive foaming in evaporation, and can result in localized accumulation of plutonium that may create a criticality hazard [CS]. 

The effect of enzymic modification on the foaming and emulsification properties of fish proteins has been studied in several laboratories (8, 14, 28). Hermansson et al. (8) observed that solvent-extracted FPC modified with an alkaline bacterial protease yielded a whipped foam volume approximately 70% greater than untreated FPC. However, the stability of the foam from the enzyme-modified FPC was about 50% less than that of the untreated FPC. The foam volume of the enzyme-modified FPC was essentially equal to that of egg white, but the foam stability of the FPC hydrolysate was substantially less. 

For the short-mix process, the oil temperature is raised to 80—90°C (175—195°F) before the addition of the caustic soda. A break between the neutral oil and soapstock takes place immediately, reducing the losses due to emulsification. The contact time between the caustic and oil is reduced to a 30-sec maximum, which helps to reduce the saponification losses. Because it is standard in Europe to degum solvent-extracted oils and to condition the oils with phosphoric acid before refining, the excess caustic treatment can be eliminated or reduced substantially. The oil is finally washed with demineralized water to help remove the traces of soap remaining in the oil and dried with processes similar to the systems used for the long-mix caustic refining process. 

Contacting of immiscible liquids, e.g. in solvent extraction processes Emulsification processes to produce stable products ... 

Ereitas S., Rudolf B., Merkle H.R, and Gander B. Flow through ultrasonic emulsification combined with static micromixing for aseptic production of microspheres by solvent extraction. Eur. J. Pharm. Biopharm. 61(3) (2005) 181-187. 

They differ from solvent extraction in their fire safety due to absence of solvent, in the possibility to extract aimed components directly from complicated pulps, in the absence of organic phase emulsification, in the reduction of extractant losses, and in the simplicity of equipment. 

The most common technique used for the preparation of PLGA nanoparticles is the emulsification-solvent evaporation technique. This technique allows the encapsulation of hydrophobic drugs and consists of dissolving the polymer and the compound in an organic solvent. The emulsion oil (O) in water (W) is prepared by adding water to a polymer solution. The nanosized droplets are induced by sonication or homogenization. The solvent is then evaporated or extracted and the nanoparticles collected after centrifugation [69,70]. 

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