Micell mixed

Separation of antibiotics and cephalosporins can be achieved successfully by CZE because most of them are ionic species. As an alternative to CZE, antibiotics and cephalosporins have been separated by MEEKC. The separation of cephalosporins in different systems (micelles, mixed micelles, and microemulsions) was investigated. The best separation was achieved in microemulsions (Fig. 4). Figure 4 shows that cephalosporins have better affinity to ME in the ME systems than in the MC systems. The affinity of cephalosporins in the ME systems decreases with decrease in the migration time. The MEEKC was also particularly suitable for neutral cephalosporins that could not be separated by CZE or MEKC (14) (see Fig. 5). The method provided good reproducibility and rapid separation with high efficiency. 

The purpose of this paper is to develop realistic specific models of mixed micellization which (i) can describe properties of ionic/nonionic surfactant mixtures and effects of salt (ii) lead to tractable calculations and (iii) can be used for extracting information on micelle mixing and monomer concentrations from the limited experimental data which are usually... 

NaAOT + Cd(AOT)2 mixtures, isooctane-H20 reversed micelles Size-quantized CdS particles generated in situ in reversed micelles Mixed surfactants favored the formation of monodispersed CdS low [H20] minimized CdS photocorrosion 615... 

Nagarajan, R. 1986. Micellization, mixed micellization and solubilization The role of interfacial interactions. Adv. Coll. Interf. Sci26 205-264. 

In this paper, a molecular thermodynamic approach is developed to predict the structural and compositional characteristics of microemulsions. The theory can be applied not only to oil-in-water and water-in-cil droplet-type microemulsions but also to bicontinuous microemulsions. This treatment constitutes an extension of our earlier approaches to micelles, mixed micelles, and solubilization but also takes into account the self-association of alcohol in the oil phase and the excluded-volume interactions among the droplets. Illustrative results are presented for an anionic surfactant (SDS) pentanol cyclohexane water NaCl system. Microstructur al features including the droplet radius, the thickness of the surfactant layer at the interface, the number of molecules of various species in a droplet, the size and composition dispersions of the droplets, and the distribution of the surfactant, oil, alcohol, and water molecules in the various microdomains are calculated. Further, the model allows the identification of the transition from a two-phase droplet-type microemulsion system to a three-phase microemulsion system involving a bicontinuous microemulsion. The persistence length of the bicontinuous microemulsion is also predicted by the model. Finally, the model permits the calculation of the interfacial tension between a microemulsion and the coexisting phase. 

In this paper, a predictive molecular thermodynamic approach is developed to calculate the structural and compositional characteristics of microemulsions. The theory applies not only to oil-in-water and water-in-oil droplet-type microemulsions but also to bicontinuous microemulsions. The treatment is an extension of our earlier theories for micelles, mixed micelles, and solubilization but also takes into account the self-association of alcohol in oil and the volume-excluded interactions among... 

The micellar solution is described using the pseudophase model (1,8,9,10), which implies that the cmc corresponds to a maximum concentration of monomers in the bulk solution above which a second phase (the micelle phase) appears. This is a very crude model which has been discussed extensively in the literature. We use it merely because it is the only one tractable in the complex media we are dealing with (ions + micelles + mixed solvent). We may write in water,... 

Mehnert implicates micelles, mixed micelles, liposomes, and drug-nanoparticles, depending on composition, as possible structures resulting from SLN preparation methods, apart from the main particulate carrier. He calls for control samples such as a liposome formulation prepared under identical conditions [40], Often, liposphere preparation procedures include a washing step with phosphate-buffered saline (PBS) to remove unencapsulated drug which possibly partly removes by-products as well. 

Therefore, micelle-forming surfactant molecules (e.g., SDS) will be present in three different forms, namely, on the lipid surface, as micelles, and as monomeric surfactant molecules in solution. Lecithin will form liposomes, which have also been detected in nanoemulsions for parenteral nutrition [77], Mixed micelles have to be considered in glycocholate/lecithin-stabilized and -related systems. Micelles, mixed micelles, and liposomes are known to solubilize drugs, and are therefore attractive alternative drug-incorporation sites (especially with respect to the low incorporation capacity of lipid crystals). 

In Fig. 16, experimental results of the time-dependent intensity after mixing proteated and deuterated PS-PB micelles in DMF under KZAC conditions [101] are shown. As can be seen the intensity decreases with time, directly showing that the micelles mix and kinetic processes are active. By analyzing the evolution of the scattered intensity and appropriate modeling, the mechanism and pathways can be determined from these experiments. In the following section, the technicalities will be described in more detail. 

TABLE 9 Enthalpies Associated with the Transfer of OG from Water into Aggregates, AHd (Micelles, Mixed Micelles, and Other Bilayers), at 27°C and 70°C... 

As noted in the reactive surfactant systems, mixing reduced the time needed to reach the value of nanoparticle uptake. Figure 17.6 shows that for the nonreactive system, a decrease in the nanoparticle concentration with time was observed followed by a plateau after around Ih of mixing at 300rpm. The decrease in nanoparticle concentration resulted from bulk precipitation of particles with sizes exceeding the stabilization capacity of the reverse micelles. Mixing improves the rate of aggregation of these particles, and hence they leave the colloidal suspension in shorter period. 

Figure 6. Because the solubility of cholesterol in aqueous systems is low, its absorption depends on the formation of detergent structures (mixed micelles) in the small intestine. Initially, when dietary fat enters the stomach and passes into the small intestine, it takes the form of relatively large lipid droplets (shown in grey). Bile acids (shown in black) reduce the surface tension in the hpid droplets, leading to the formation of smaller structures (mixed micelles). Mixed micelles consist of an outer sheU of bile acids, monoacylglycerols, phospholipids and lysolecithin, and an inner core of digestion products of fats such as fatty acids, monoacylglycerols, cholesterol (of which 90% infreeform), andfat-soluble micronutrients.

Kwak M, Musser AJ, Lee J, Herrmann A (2010) DNA-functionalised blend micelles mix and fix polymeric hybrid nanostructures. Chem Commun 46 4935-4937... 

The thermodynamic equilibria of amphiphilic molecules in solution involve four fundamental processes (1) dissolution of amphiphiles into solution (2) aggregation of dissolved amphiphiles (3) adsorption of dissolved amphiphiles at an interface and (4) spreading of amphiphiles from their bulk phase directly to the interface (Fig. 1.1). All but the last of these processes are presented and discussed throughout this book from the thermodynamic standpoint (especially from that of Gibbs s phase rule), and the type of thermodynamic treatment that should be adopted for each is clarified. These discussions are conducted from a theoretical point of view centered on dilute aqueous solutions the solutions dealt with are mostly those of the ionic surfactants with which the author s studies have been concerned. The theoretical treatment of ionic surfactants can easily be adapted to nonionic surfactants. The author has also concentrated on recent applications of micelles, such as solubilization into micelles, mixed micelle formation, micellar catalysis, the protochemical mechanisms of the micellar systems, and the interaction between amphiphiles and polymers. Fortunately, almost all of these subjects have been his primary research interests, and therefore this book covers, in many respects, the fundamental treatment of colloidal systems. 

Table 1 Kinetic parameters of MGDG synthase in mixed micelles. Mixed micelles were prepared as described by [5]. MGDG synthase activity was determined with various diacylglycerol molecular species as the varied substrate. Diacylglycerol concentration was expressed as mole fraction, i.e. [diacylglycerol]/([CHAPS] + [PG] -i- [diacylglycerol]). The Vmax and app Km values were respectively calculated from the IfV intercept and the 1/[substrate], expressed as mole fraction, intercept axes of double reciprocal plots. Diacylglycerol concentration within a micelle was also expressed as the number of diacylglycerol molecules per micelle, assuming that each 90 kDa-mixed micelle contains about 140 molecules of CHAPS, PG and diacylglycerol.

Muller and Johnson [28] studied the effect of organic additives on sodium 12,12,12-trifluorododecyl sulfate micelles. Mixed solvents used in the study included aqueous urea, glycine, glycerol, acetamide, methanol, ethanol, acetone. 

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