Light scattering technique interpretation

Light scattering technique was used in determining the oil solubilization rate. Debye s equation ( ) was used in the interpretation. The basic principle involves the measurement of the surfactant aggregate size during the solubilization. As the oil goes into the surfactant micelle, the increased size will be reflected by the turbidity of the solution. 

Dynamic light scattering (DLS) techniques measure the fluctuations in the scattered light intensity caused by the random Brownian motion of the dispersed particles. The use of a theoretical model of particle Brownian motion enables us to extract particle size from DLS data. Other dynamic light scattering techniques such as electrophoretic light scattering (ELS) study collective particle motions. Theoretical interpretation of ELS data leads to other particle properties such as electrophoretic mobility fi and zeta potential f. These techniques will be discussed in more detail in subsequent sections. 

In a series of papers using light-scattering techniques, Prins and coworkers " have interpreted their data in terms of spinodal... 

Besides pcs, other light scattering techniques including Brillouin scattering and Fabry-Perot interferometry described in previous sections have been applied to probe the dynamics of polymers at higher frequencies than the more conventional techniques. Interpretations of the results from these techniques are still subjects of controversy and are not discussed here. 

A number of experimental techniques by measurements of physical properties (interfacial tension, surface tension, osmotic pressure, conductivity, density change) applicable in aqueous systems suffer frequently from insufficient sensitivity at low CMC values in hydrocarbon solvents. Some surfactants in hydrocarbon solvents do not give an identifiable CMC the conventional properties of the hydrocarbon solvent solutions of surfactant compounds can be interpreted as a continuous aggregation from which the apparent aggregation number can be calculated. Other, quite successful, techniques (light scattering, solubilization, fluorescence indicator) were applied to a number of CMCs, e.g., alkylammonium salts, carboxylates, sulfonates and sodium bis(2-ethylhexyl)succinate (AOT) in hydrocarbon solvents, see Table 3.1 (Eicke, 1980 Kertes, 1977 Kertes and Gutman, 1976 Luisi and Straub, 1984 Preston, 1948). 

Electron microscopy (5,40,52,63, 64), on the other hand, can provide direct information on the domain structure under favorable conditions, such as when the domains are crystalline. When the samples exhibit a semicrystalline superstructure, small-angle light scattering and polarized microscopy have been used in addition to electron microscopy to study the spherulitic structure. These methods are complemented by differential scanning calorimetry, and various techniques for studying dynamic mechanical behavior which can be interpreted to give additional, if somewhat less direct, information on domain structure. 

We shall not pursue this approach here because it does not help us much in finding a molecular interpretation, certainly not for U°. Even in the absence of waves (solidified liquids), U° is substantial. Rather, this interpretation deals with a contribution to y than with y itself. However, we recall that the capillary wave connection had already occurred in the technique for measuring surface tensions from surface light scattering, see Mandelstam s equation [1.10.1], from which an explicit formula for y may be derived. 

One technique for doing this is to count the particles microscopically. In addition to particle size limitation, this is an extraordinarily tedious procedure. Light scattering can be also used for the kinetic study of aggregation, but experimental turbidities must be interpreted in terms of the number and size of the scattering particles. 

Drug Substance (DS) Specific Surface Area (SSA) has been estimated by permeabilimetry, gas adsorption, laser light scattering and Mercury Intrusion Porosimetry (MIP). Because of the simplifying and different assumptions made, none of these experimental methods can provide the absolute SSA value and a perfect agreement between the values obtained by each technique is not found However, differences in theoretical assumptions made for each technique and observed results have been useful for understanding and interpreting the texture of the powder studied. 

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