Emulsions components

Emulsion components enter the stratum corneum and other epidermal layers at different rates. Most of the water evaporates, and a residue of emulsifiers, Hpids, and other nonvolatile constituents remains on the skin. Some of these materials and other product ingredients may permeate the skin others remain on the surface. If the blend of nonvolatiles materially reduces the evaporative loss of water from the skin, known as the transepidermal water loss (TEWL), the film is identified as occlusive. AppHcation of a layer of petrolatum to normal skin can reduce the TEWL, which is normally about 4—8 g/(m h), by as much as 50 to 75% for several hours. The evaporated water is to a large extent trapped under the occlusive layer hydrating or moisturizing the dead cells of the stratum corneum. The flexibiHty of isolated stratum corneum is dependent on the presence of water dry stratum corneum is britde and difficult to stretch or bend. Thus, any increase in the water content of skin is beHeved to improve the skin quaHty. 

Determination of drug potency in the presence of other emulsion components may require development of special analytical techniques for example, oils may interfere with standard reverse phase HPLC assays, requiring extraction techniques or the development of normal phase assays. Similarly, bioassays may give erroneous results when the drug is presented in an emulsion form. Hence, adequate controls and/or extraction techniques must be developed to give reliable values from the bioassay. 

It has to be clear that, once diluted and injected (or administered in ocular and other routes), the emulsion stability and fate are determined by three measurable parameters. The first is the partition coefficient of each emulsion component (including added drugs and agents) between the emulsion assembly and the medium. To some extent this partition coefficient is related to oil-water and/or octanol-water partition coefficients. For example, it was well demonstrated that per component of which logP is lower than 8, the stability upon intravenous (IV) injection is questionable [42,138], The other two parameters are kQff, a kinetic parameter which describes the desorption rate of an emulsion component from the assembly, and kc, the rate of clearance of the emulsion from the site of administration. This approach is useful to decide if and what application a drug delivery system will have a chance to perform well [89],... 

Characterization of such emulsions therefore often involves three phases the water phase, the oil phase, and the solids. Complete characterization of an emulsion could therefore involve detailed chemical and physical analysis of all of the emulsion components, as well as any bulk properties that might be of interest (viscosity, density, etc.). This level of detail is clearly beyond the scope of this discussion. For the purposes of this chapter, emulsion characterization will be defined as the quantification of the phases present, the determination of the nature and size distribution of... 

The characterization techniques that will be discussed here are used in field situations, on-line, and in the laboratory. In order to characterize an emulsion, it is necessary to determine the amount of each phase present, the nature of the dispersed and continuous phases, and the size distribution of the dispersed phase. The stability of an emulsion is another important property that can be monitored in a variety of ways, but most often, from a processing point of view, stability is measured in terms of the rate of phase separation over time. This phenomenological approach serves well in process situations in which emulsion formation and breaking problems can be very site specific. However, emulsion stability is ultimately related to the detailed chemistry and physics of the emulsion components and their interactions, and these details cannot be completely ignored. 

Figure 29. NIR spectrum of an oil-sand sample illustrating peaks due to clay minerals (C), oil (O), and water (W) phases. These spectra can be obtained via fiber optics therefore, this technique has the potential for on-line quantification of oil, water, and mineral emulsion components. Either fundamentals, first combinations, or first overtones can be used to quantify particular emulsion components. The method requires calibration with standards that can be difficult, given complex field emulsions.

Bottle (or beaker or jar) tests are commonly used to evaluate emulsifier and demulsifier performances. Samples of the emulsion components and the emulsifier to be tested, or of an existing emulsion and the demulsifier to be tested, are mixed in bottles, beakers or jars in a specified way, and then let them stand for a specified period of time. Depending on the process being tested or developed, other additives (e.g. diluents) may be added, the temperature may be varied or the samples may be centrifuged. After a defined period of time, the stabilized or destabilized emulsions are examined. In the stabilizing of emulsions, one looks for a stable. 

Finally, the presence of surfactant always raises the possibility of micelle formation in the primary continuous phase and the subsequent solubilization of the primary dispersed phase. Solubilization, therefore, represents a convenient mechanism for the transport of primary emulsion components to the secondary continuous phase. Such a solubilization process also represents a convenient mechanism for the transport of material. In the context of a critical application such as controlled drug delivery, in which the mechanism of delivery is diffusion-controlled, such breakdown mechanisms would be very detrimental to the action of the system since they could result in a rapid release of active solute with possibly dangerous effects. 

Influence of Emulsion Components on Rheoiogicai Properties and Dropiet Size... 

To analyze the influence of emulsion components on rheological properties and droplet size a statistical analysis of form... 

Epple M —) Maas M Felddtd Z Pettersson T Fischer K —> Diehl C Fluegel S Diehl C Gutberlet T Kolasihska M Hloucha M Kettler E Hoffmann H Song A Kappl M Zhang L Ketder E, Muller CB, Klemp R, Hloucha M, DOring T, von Rybinski W, Richtering W Polymer-Stabilized Emulsions Influence of Emulsion Components... 

Sagitani has described an alternative method for producing fine 0/W emulsions called surfactant-phase emulsification . Here, the addition of polyols like 1,3-butanediol to the usual emulsion components oil, water and surfactant is necessary. In the method, oil is added dropwise to an isotropic solution of concentrated surfactant in a water/polyol mixture. A clear gel eventually forms which is an oil-... 

Chem. Descrip. Montan acid wax and montan wax CAS 68476-03-9 8002-53-7 EINECS/ELINCS 270-664-6 232-313-5 Uses Solubilizer for dye bases emulsifying component for wax emulsions component for lubricating greases Features Hard wax... 

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