Dynamic light scattering method

Xiang, T.-X. Anderson, B. D., Development of a combined NMR paramagnetic ion-induced line-broadening dynamic light scattering method for permeability measurements across lipid bilayer membranes, J. Pharm. Sci. 84, 1308-1315 (1995). 

Standard static and dynamic light scattering methods assume that there is very little multiple scattering by the particles, that is, the dispersion has to be sufficiently dilute so that the photons are scattered only once as they pass through the sample. Is there a way to look inside a dispersion that is cloudy or milky, such as a foam, and to extract information on the local structure and its kinetics and relaxation Or, is it possible to tailor a dispersion so that... 

The relation between the catalytic and aggregation properties of the copolymers was shown using the dynamic light scattering method. Hydro-dynamic radius distributions obtained by processing light scattering data showed that at temperatures below 35 °C the copolymers existed in the form... 

Dynamic light scattering methods were used to study reverse micelle and microemulsion phases formed in liquid and supercritical alkane continuous phases. 

Dynamic Light Scattering Methods Dynamic light scattering (DLS) is now used on a routine basis for the analysis ofparticle sizes in the submicrometer range. It provides an estimation of the average size and its distribution within a measuring time of a few minutes. 

Size of the liposomes should be between 100 and 200 nm for best circulation times in vivo, this can be checked by a dynamic light scattering method. The size dependency has to do with accumulation in the liver, ability to extravasate into tissues, and any possible immune reactions. 

These macroscopic viscosity measurements have been confirmed at the molecular level. For example, dynamic light-scattering methods show an average hydrodynamic diameter (D J of about 370 A for a 50/50 copolymer of NVP/SPE in low salt (<2%) and a of about 390 A in high-salt (20% NaCl) concentrations (18). Moreover, in solutions of water or low concentrations of salt, solvent quality (as measured by second virial coefficient, A2) decreases with increasing levels of SPE. LALLS measurements for NVP/SPE 80/20 and 10/90 copolymers in 2% NaCl solution yielded molecular weights of 1.1 X 10 and 1.4 x 10 g mol respectively. The same compositions yielded second virial coefficients of 9.0 X 10 and 0.6 X 10 , respectively. In this case, a higher virial coefficient means better solution quality. 

In the Dynamic Light Scattering method (also known as Photon Correlation Spectroscopy), one measures the diffusion of macromolecular chains in solution. The diffusion coefficient is related to the molar mass. The method suffers a number of difficulties. Raw experimental data do not lend themselves to immediate interpretation and must be fitted using a model MMD. Furthermore, D5mamic LS cannot be used to choose between a unimodal MMD and bimodal MMD. In fact data are fitted using a model MMD and the number of parameters to be fitted increases quickly, going from unimodal to bimodal (a bimodal MMD requires finding the best fit of six parameters). 

The dynamic light scattering method cannot be applied for emulsions since these cannot be prepared in a monodisperse form. However, by measuring the adsorbed layer thickness on a model monodisperse hydrophobic particle such as polystyrene, one can make the assumption that the layer thickness is similar to that obtained on an emulsion droplet. 

Earlier we have demonstrated the ability of MR to increase surface activity of lysozyme [4], We used phosphate buffer with pH 7.4,1 = 0.05 M as a solvent, that is corresponds to the conditions of lysozyme catalytic activity determination in the presence of MR [1], However using dynamic light scattering method we have shown that there were associates (or aggregates) of some lysozyme molecules in solution at this pH value. To avoid this effect we changed the pH value from 7.4 to 6.0. 

The average particle size as well as the particle size distribution of the prepared lattices was investigated under reaction state concentration using a novel dynamic light scattering method. Table 1 summarizes relevant data of the prepared products. Furthermore, the composition of the monomer feed as well as the composition of the polymer is given in Table 1. The polymer composition has been calculated from elemental analysis data. 

All the gel moduli can be defined by a combination of the static and dynamic light scattering methods. 

As can be seen in the particle-size measurements (cf. Figure 14.4) and cryo-TEM images (cf. Figure 14.5), the mean particle sizes for Stober- and alkali-silicate sols vary around 21 and 40 nm, respectively, independent of the pH value. The smaller particles of the Stober-sol show a narrow distribution. As shown in Figure 14.5, the fumed silica consists of aggregates built by flame fusion of smaller spherical primary particles. Their real size cannot be measured exactly by the dynamic light scattering method... 

Size and size distribution Dynamic light scattering method Gel Permeation Chromatography Size Exclusion Chromatography... 

Chain length Dynamic light scattering method... 

Table 2 values obtained from the dynamic light-scattering method and deduced from the... 

Close to the phase transitions point (such as the weak first-order isotropic to nematic transition or the second-order nematic to smectic transition), the order of the low-temperature phase occurs transiently in the finite small size of fluctuations, which is called cybotactic clusters. When the correlation length of the fluctuation increases towards the transition point, the relaxation time diverges. For example, near the nematic-smectic phase transition point, it can be seen that the correlation length becomes longer towards the transition point by X-ray diffraction experiments (Fig. 10.21). In addition, the increase of the relaxation time of the fluctuations can be measured using dynamic light scattering method, which wiU be introduced in detail in Sect. 10.4.3.2. 

Classical light scattering method Dynamic light scattering method National Bmcau of Standards, USA (now National Institute of Standard and Technology, NIST)... 

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