Emulsion specific adsorption

When the electrostatic stabilization of the emulsion is considered, the electrolytes (monovalent and divalent) added to the mixture are the major destabilizing species. The zeta potential of the emulsion particles is a function of the concentration and type of electrolytes present. Two types of emulsion particle-electrolyte (ions) interaction are proposed non-specific and specific adsorption.f H non-specific adsorption the ions are bound to the emulsion particle only by electrical double-layer interactions with the charged surface. As the electrolyte concentration is increased, the zeta potential asymptotes to zero. As the electrostatic repulsion decreases, a point can be found where the attractive van der Waals force is equal to the repulsive electrostatic force and flocculation of the emulsion occurs (Fig. 9A). This point is called the critical flocculation concentration (CFC). 

Sensitizers as well as desensitizers form a reversal oxidoreduction system with silver halides, according to both pH and pAg of the photographic emulsion. But besides the specific influence of the emulsion, the efficiency of a sensitizing dye depends on many other factors such as its adsorption, its spectral absorption, the energetic transfer yield, the dye aggregate to the silver halide, and finally on its desensitizing property in... 

In cases, of acute emulsion-problems substances like-anion exchangers alumina or silicagel are used specifically to resolve the problem by adsorption of the emulsifying agents. In fact, it would be advisable to employ the technique of column chromatography for the effective separation of the analyte as compared to an extraction process. 

This broad class of hydrolases constitutes a special category of enzymes which bind to and conduct their catalytic functions at the interface between the aqueous solution and the surface of membranes, vesicles, or emulsions. In order to explain the kinetics of lipolysis, one must determine the rates and affinities that govern enzyme adsorption to the interface of insoluble lipid structures -. One must also account for the special properties of the lipid surface as well as for the ability of enzymes to scooC along the lipid surface. See specific enzyme Micelle Interfacial Catalysis... 

By comparing interfacial inactivation rates in a stirred-cell (low and controlled area of exchange) and an emulsion system (high interfacial area), these authors have shown that the use of an emulsion system can be exploited to obtain high solute interphase mass-transfer rates since the rate of specific interfacial inactivation remains low. However, in this system, the presence of an epoxide substrate at high concentration in the organic phase increases the rate of interfacial inactivation. Addition of a sacrificial protein to the system, which can prevent adsorption of the catalytic enzyme at the interface, could provide a method to reduce the rate of interfacial inactivation. 

Non-dairy creams (cream alternatives) are O/W emulsions stabilized by milk proteins. A relatively thick adsorption layer provides stability, mostly by steric stabilization and partly by electrostatic stabilization [829]. Figure 13.3 shows an example of a soybean-oil and milk-protein emulsion stabilized by fat globules and protein membranes. Stabilizers, such as hydrocolloid polysaccharides, are added to increase the continuous phase viscosity and reduce the extent of creaming. They must be stable enough to have a useful shelf-life but de-stabilize in a specific way when they are... 

Absorption. The possible color of the last mentioned emulsion needs further explanation. Up till now, we have implicitly assumed that light is only scattered, not absorbed. If absorption occurs, we should use the complex refractive index h = n — in, where ri determines the adsorption (i = yj — 1). The relations now become more complicated, n is related to the specific extinction y according to y Ann /X. The absorbency as determined... 

A non-equilibrium state of the adsorption layer of bubbles or drops initiates adsorption processes in foams and emulsions. Transport of surface active substances in foams and emulsions can additionally be complicated by this dynamic adsorption layer. Specifically, water purification from surfactant or their fractionation are strongly influenced by a dynamic state of the adsorption layer (Section 8.8.3). 

EDM with experiments using l.d.c. emulsions and s.d.e. may result in (1) the quantification of emulsion film stability, namely, the establishment of the coalescence time dependence on the physicochemical specificity of the adsorption layer of a surfactant (polymer), its structure, and the droplet dimensions. This quantification can form a basis for the optimization of emul-sifier and demulsiner selection and synthesis for emulsion technology applications, instead of the current empirical level applied in this area and (2) the elaboration of a commercial device for coalescencetime measurement, which in combination with EDM will represent a useful approach to the optimization of emulsion technology with respect to stabilization and destabilizatioa... 

There is some controversy as to whether adsorption occurs in emulsion counting of Na2 C03 (Wigfield, 1976). Our results agree with those of that author in that we have not seen effects that could be attributed to adsorption. Furthermore we have never had ciny problems with low count rates when using counting mixtures of the recommended ccanpositions even with the highest specific activity Na2 C0j we used (59.5 mCi/mmol). The maximum specific activity theoretically possible for Na2 C03 at 100% isotopic abundance is 64 mCi/mmol (Wilson, 1966). 

Table 4 shows that, as in the TRS 10-410 series, the specific refraction of each PDM-334 microemulsion increases following adsorption. All post-adsorption microemulsions therefore again have higher oil to brine ratios than the initial microemulsions. The interfacial tension behavior is also similar to that observed with the TRS 10-410 micro emulsions (Figure 3) all values are decreased and all values are increased as a result of adsorption. Again the y values for the n-butanol microemulsion both before and after adsorption lie above the y curves. 

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