Emulsions globule size

For parenteral products specific consideration needs to be included for tonicity adjustment, emulsion globule size, ease of resuspension and sedimentation rate, particle size and particle size distribution, viscosity and syringeability, and crystal form changes. Full consideration should be included of the proposed instructions for dilution or reconstitution of products and of compatibility with the proposed solvents or diluents. This should include a demonstration that the proposed storage temperature and extremes of concentration are suitable. 

Fig. 7 Schematic representation of colloid mill and microphotographs showing emulsion globule size before and after milling. (Courtesy of Premier Mill Corp., Reading, Pennsylvania.)...

The coupled equations had been solved by numerical computation using an implicit finite difference technique [34]. While solving the above equations, the emulsion globule size J32 (sauter mean diameter) was calculated by using the following correlation [35] ... 

Very finely disperse solids, which are adsorbed at the liquid/liquid interfaces, forming films of particles around the disperse globules. Certain powders can very effectively stabilize against coalescence. The solid s particle size must be very small compared with the emulsion droplet size and must exhibit an appropriate angle of contact at the three-phase (oil/water/solid) boundary [141]. 

The process involves removal of materials less dense than water (such as oil) and suspended materials that are more dense than water by settling. The API separator does not separate substances in solution, nor does it break emulsions. The effectiveness of a separator depends on the temperature of the water, the density and size of the oil globules, and the amounts and characteristics of the suspended materials. The susceptibility to separation (STS) test is normally used as a guide to determine what portion of the influent to a separator is amenable to gravity separation [38]. In terms of globule size, an API separator is effective down to globule diameters of 0.015 cm (15 microns). 

Nakai and Le (1970) have used a different approach to the measurement of fat by light scattering. They dissolved both the fat and protein particles with acetic acid, measured the protein content by the absorbance at 280 nm, and then reformed a fat emulsion by adding a solution of urea and imidazole. The turbidity was measured at 400 nm and was found to be independent of the initial fat globule size distribution. 

Walstra, P. 1968. Estimating globule-size distribution of oil-in-water emulsions by spec-troturbidimetry. J. Coll. Interf. Sci. 27, 493-500. 

Figures 9 and 10 show the fat surface area and the relative width of the globule size distribution, respectively, of all the protein stabilized emulsions as a function of the number of passes at a power consumption of 40 W (11). As can be seen from Figures 9 and 10 an increase in number o7 passes does not noticably enhance the final fat surface area of the protein stabilized emulsions, but affects more the distribution width by a decrease and a final level off. The caseinates at both ionic strengths produce emulsions of the smallest surface area and the narrowest distribution widths. The WPC stabilized emulsions have larger surface areas and wider spread in globule size than emulsions stabilized...

Teramoto et al. [15] and Bunge and Noble [16] incorporated reaction reversibility in describing the transport process in the emulsion globule. Teramoto et al. [15,17,18] also developed models that accounted for diffusion in the emulsion drops and the drop-size distribution of the W/O emulsion. Kataoka and coworkers [19,20] developed the work of Teramoto et al. [15,17,18] by proposing a model with parameters that could be determined independently or through correlations in the literature. 

If k is significant, polydispersity of the emulsion globules will need to be considered since the Biot number is dependent on globule size. Correlations for k are available in the literature [33,41,74—80]. Distribution coefficient data should be experimentally determined for a given system. Data for some systems are available from the literaffire [21,38,42,81-83]. 

Emulsions - liquid dispersions usually of an oil phase and an aqueous phase - are a traditional pharmaceutical dosage form. Oil-inwater systems have enjoyed a renaissance as vehicles for the delivery of lipid-soluble dmgs (e.g. propofol). Their use as a dosage form necessitates an understanding of the factors governing the formulation and stability of oil-in-water (o/w) and water-in-oil (w/o) emulsions, multiple emulsions (w/o/w or o/w/o) and microemulsions, which occupy a position between swollen micelles and emulsions with very small globule sizes. Photomicrographs of o/w, w/o systems and multiple emulsions are shown in Fig. 7.10. It is also possible to formulate nonaqueous or anhydrous emulsions, that is oil-in-oil systems and even multiple oil-in-oil-in-oil systems. 

Figure 7.13 Variation of mean globule size in a mineral oil-in-water emulsion as a function of the HLB of the surfactant mixtures present at a level of 2.5%. Surfactants Brij 92-Brij 96 mixtures.

The average size of the emulsion globules as measured by size frequency analysis of microphotographs with the help of a catheto-meter was found to be 1.2 pm. (See Figures 1 and 2)... 

The simplest mode of LM operation available is a batch reactor. The LM emulsions containing enzymes or cells are kept agitated in a vessel by using impellers. Periodic samples of external aqueous phase can be taken to monitor the reaction rate it is much more difficult to monitor the conditions in the internal aqueous phase. Impeller speed becomes an important parameter in batch operation, as it determines the size of the emulsion globules and therefore influences the emulsion stability and the mass-transfer resistance (46). 

Figure 4-4 Reaction front progress inside emulsion globules of various sizes with same sauter mean diameter of0.065 cm. From Ref. [33] with permission.

Dg, effective diffusivity of metal ions in saturated zone of emulsion globules fj, volume fraction of emulsion globules of/th size... 

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