Micelles analytical applications

Oxine (5) fonns complexes of analytical applicability with various metal ions. A RP-HPLC-FLD method (Xex = 370 nm, Xg = 516 nm) was proposed for simultaneous determination of Al(III) and Mg(II), using a Cjg column. Various details of the method are noteworthy Optimization of the method showed that for both ions it is best to have also precolumn and in-column complex formation, caused by the presence of 5 in the injection loop and in the carrier solution FLD detection is preferable to simple UVD because it avoids the background of 5 and interference of various ions forming nonfluorescent chromogenic complexes, e.g. Ca(II) and Zn(II) the intensity of the fluorescence can be increased by micelle formation on addition of SDS and neutralized Af,Af-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid (6). The LOD (SNR = 3) were 0.74 (xM (18 ppb) Mg(n) and 0.60 (xM (16 ppb) Al(III) the latter was attributed in part to residual impurities in the purified water -... 

In THE PAST DECADE, IMPROVEMENTS IN infrared spectroscopic instrumentation have contributed to significant advances in the traditional analytical applications of the technique. Progress in the application of Fourier transform infrared spectroscopy to physiochemical studies of colloidal assemblies and interfaces has been more uneven, however. While much Fourier transform infrared spectroscopic work has been generated about the structure of lipid bilayers and vesicles, considerably less is available on the subjects of micelles, liquid crystals, or other structures adopted by synthetic surfactants in water. In the area of interfacial chemistry, much of the infrared spectroscopic work, both on the adsorption of polymers or proteins and on the adsorption of surfactants forming so called "self-assembled" mono- and multilayers, has transpired only in the last five years or so. 

Micelles and other organized surfactant aggregates are increasingly utilized in analytical applications (1.)- They interact with reagents and alter spectroscopic and electrochemical properties which, in turn, often results in increased sensitivities. Organized assemblies have also been employed in separation processes. Gas, liquid and thin layer micellar chromatographic techniques have been developed (2). 

In early July 1980, a session devoted to the analytical applications of micelles was given as part of the International Symposium on Solution Behavior of Surfactants (in Potsdam, NY). It was a huge success, often... 

Monomers of die type Aa B. are used in step-growth polymerization to produce a variety of polymer architectures, including stars, dendrimers, and hyperbranched polymers.26 28 The unique architecture imparts properties distinctly different from linear polymers of similar compositions. These materials are finding applications in areas such as resin modification, micelles and encapsulation, liquid crystals, pharmaceuticals, catalysis, electroluminescent devices, and analytical chemistry. 

As mentioned earlier, reversed micelles have different properties from normal micelles. These properties have the potential to favorably affect the sensitivity and other analytical aspects of CL reactions. Thus, reversed micelles have been used to prolong the duration of the observed CL of various oxalate ester (or acid)-hydrogen peroxide-sensitizer reaction systems for application as chemical light sources [62],... 

Many pharmaceutical preparations contain multiple components with a wide array of physico-chemical properties. Although CZE is a very effective means of separation for ionic species, an additional selectivity factor is required to discriminate neutral analytes in CE. Terabe first introduced the concept of micellar electrokinetic capillary chromatography (MEKC) in which ionic surfactants were included in the running buffer at a concentration above the critical micelle concentration (CMC) [17], Micelles, which have hydrophobic interiors and anionic exteriors, serve as a pseudostation-ary phase, which is pumped electrophoretically. Separations are based on the differential association of analytes with the micelle. Interactions between the analyte and micelles may be due to any one or a combination of the following electrostatic interactions, hydrogen bonding, and/or hydro-phobic interactions. The applicability of MEKC is limited in some cases to small molecules and peptides due to the physical size of macromolecules... 

Lastly, it may be possible to recover some analytes from the micellar/surfactant media by distillation. Several patent reports claim that materials (mostly essential or edible oils) can be recovered from highly concentrated micelles in this manner (520.521). The abstracts are too vague to judge the relative merit of this procedure or whether it is applicable to actual separation science problems. Further work is obviously required in this area. 

The functionalization of the reverse micelles will create a novel application in bioseparation processes in the analytical and medical sciences. It is therefore important to reveal the recognition mechanism of proteins at the liquid-liquid interface in reversed micellar solutions. DNA is also successfully extracted in a few hours by reversed micelles formed by cationic surfactants in isooctane. The driving force of the DNA transfer is the electrostatic interaction between the cationic surfactants and the negatively charged DNA. Another important factor is the hydrophobicity of the cationic surfactants. Doublechain type cationic surfactants are found to be one of the best surfactants ensuring the efficient extraction of DNA. These results have shown that reverse micellar solutions will become a useful tool not only for protein separation, but also for DNA separation. 

A crucial parameter-free test of the theory is provided by its application to micelle formation from ionic surfactants in dilute solution [47]. There, if we accept that the Poisson-Boltzmann equation provides a sufficiently reasonable description of electrostatic interactions, the surface free energy of an aggregate of radius R and aggregation number N can be calculated horn the electrostatic free energy analytically. The whole surface free energy can be decomposed into two terms, one electrostatic, and another due to short-range molecular interactions that, from dimensional considerations, must be proportional to area per surfactant molecule, i.e. 

Basically, MEKC is an EKC application with the micelle as the designated carrier. A surfactant at a concentration above the CMC is added to the running buffer and initiates micelle formation. Because the separation principle has already been dealt with and the flow scheme in Fig. 3 is an illustrative summary notated for MEKC, it is clear that a neutral analyte residing in the hydrophobic interior of a micelle (depicted as a sphere in Fig. 3) will be transported with the micelle s velocity (Wmc)- The free analyte will migrate with the electro-osmotic flow velocity... 

In this section, we will present the most significant and recent literature data concerning the UV-visible absorption and luminescence spectroscopies of a variety of phenothiazine derivatives and BPHTs (Figs. 1-5). We will also describe the photophysical and photochemical properties as well as the characteristics of organized media or molecular complexes formed between a number of phenothiazine derivatives or BPHTs and either micelles or CDs. Finally, we will examine several analytical methods which have been developed to determine phenothiazines in biological samples and pharmaceutical formulations, due to biomedical interest, and other recent applications of phenothiazines and BPHTs in various fields. 

Spreadsheet Summary In the final exercise in Chapter 15 of Applications of Microsoft Excel in Analytical Chemistry, xnict] a.r electroki-netic capillary chromatography is used to determine the critical micelle concentration (CMC) of a surfactant. An equation is developed to relate the retention factor to the CMC. Measured retention times are then used to determine the CMC from a regression analysis. 

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