Micellar determination

The binding behaviour of benzene can be extrapolated to many other aromatic compounds such as naphthalene and benzene derivativesInterestingly, a large number of probe molecules contain aromatic rings and many of them will prefer the outer regions of micelles, whereas in bilayer systems, the same molecules prefer the interior of the aggregate ". Qearly these probes cannot be used to determine polarity of the micellar interior or the extent of water penetration therein . 

Unfortunately, more detailed kinetic studies aimed at the determination of the second-order rate constants in the micellar pseudophase have not been published. 

Vogt, C. Conradi, S. Rhode, E. Determination of Caffeine and Other Purine Compounds in Pood and Pharmaceuticals by Micellar Electrokinetic Chromatography, /. Chem. Educ. 1997, 74, 1126-1130. 

These effects appearance is explained by the nature of hydrophobic interactions and the stixrctural organization of micellar solutions. The host-guest phenomena determine the increase of the selectivity of analytical reactions in the surf actant-based organized systems. 

In this study we examined the influence of concentration conditions, acidity of solutions, and electrolytes inclusions on the liophilic properties of the surfactant-rich phases of polyethoxylated alkylphenols OP-7 and OP-10 at the cloud point temperature. The liophilic properties of micellar phases formed under different conditions were determined by the estimation of effective hydration values and solvatation free energy of methylene and carboxyl groups at cloud-point extraction of aliphatic acids. It was demonstrated that micellar phases formed from the low concentrated aqueous solutions of the surfactant have more hydrophobic properties than the phases resulting from highly concentrated solutions. The influence of media acidity on the liophilic properties of the surfactant phases was also exposed. 

POLYCYCLIC AROMATIC HYDROCARBONS LUMINESCENCE DETERMINATION USING MICELLAR SOLUTIONS... 

The aim of this work is the development of pyrene determination in gasoline and contaminated soils. For this purpose we used room temperature phosphorescence (RTP) in micellar solutions of sodium dodecylsulphate (SDS). For pyrene extraction from contaminated soils hexane was used. Then exttacts earned in glass and dried. After that remains was dissolved in SDS solution in the presence of sodium sulphite as deoxygenation agent and thallium (I) nitrate as heavy atom . For pyrene RTP excitation 337 nm wavelength was used. To check the accuracy of the procedures proposed for pyrene determining by RTP, the pyrene concentrations in the same gasoline samples were also measured by GC-MS. 

For fluorescence PAH determination in tap water acid-induced cloud point extraction was used. This kind of extraction based on the phase separation into two isotropic liquid phases a concentrated phase containing most of the surfactant (surfactant-rich phase), where the solubilised solutes are exttacted, and an aqueous phase containing a surfactant concenttation closes to the critical micellar concentration. 

Hydrophobicity inflkence. Despite of the diphilic character of the NS-rich phase the efficiency of micellar extraction raises with general substrate hydrophobicity increase. The hydrophobicity of ligand is the main factor, which determines the cloud point extraction of complexes. 

Strkcttire inflkence. The specificity of interphase transfer in the micellar-extraction systems is the independent and cooperative influence of the substrate molecular structure - the first-order molecular connectivity indexes) and hydrophobicity (log P - the distribution coefficient value in the water-octanole system) on its distribution between the water and the surfactant-rich phases. The possibility of substrates distribution and their D-values prediction in the cloud point extraction systems using regressions, which consider the log P and values was shown. Here the specificity of the micellar extraction is determined by the appearance of the host-guest phenomenon at molecular level and the high level of stmctural organization of the micellar phase itself. 

On the basis of data obtained the possibility of substrates distribution and their D-values prediction using the regressions which consider the hydrophobicity and stmcture of amines was investigated. The hydrophobicity of amines was estimated by the distribution coefficient value in the water-octanole system (Ig P). The molecular structure of aromatic amines was characterized by the first-order molecular connectivity indexes ( x)- H was shown the independent and cooperative influence of the Ig P and parameters of amines on their distribution. Evidently, this fact demonstrates the host-guest phenomenon which is inherent to the organized media. The obtained in the research data were used for optimization of the conditions of micellar-extraction preconcentrating of metal ions with amines into the NS-rich phase with the following determination by atomic-absorption method. 

USING OF THE MICELLAR MEDIUM, BASIC DYES AND PRECONCENTRATION ON THE POLYURETHANE FOAMS FOR THE DETERMINATION OF PHOSPHORUS AND ARSENIC... 

DETERMINATION OF 1-OCTANOL - WATER AND MICELLAR PSEUDOPHASE - WATER PARTITION COEFFICIENTS OF BENZODIAZEPINES... 

Distribution of benzodiazepines in system micellar pseudophase - water was investigated in micellar solutions of sodium dodecylsulfate. The protonization constants of benzodiazepines were determined by the UV-spectophotometry. Values of protonization constants increase with increasing of sodium dodecylsulfate concentration. The binding constants of two protolytic forms of benzodiazepines with a micellar pseudo-phase and P, values were evaluated from obtained dependence. 

The aqueous micellai solutions of some surfactants exhibit the cloud point, or turbidity, phenomenon when the solution is heated or cooled above or below a certain temperature. Then the phase sepai ation into two isotropic liquid phases occurs a concentrated phase containing most of the surfactant and an aqueous phase containing a surfactant concentration close to the critical micellar concentration. The anionic surfactant solutions show this phenomenon in acid media without any temperature modifications. The aim of the present work is to explore the analytical possibilities of acid-induced cloud point extraction in the extraction and preconcentration of polycyclic ai omatic hydrocai bons (PAHs) from water solutions. The combination of extraction, preconcentration and luminescence detection of PAHs in one step under their trace determination in objects mentioned allows to exclude the use of lai ge volumes of expensive, high-purity and toxic organic solvents and replace the known time and solvent consuming procedures by more simple and convenient methods. 

J. V. Posluszny and R. Weinberger, Determination of dmg substances in biological fluids by direct injection multidimensional liquid cliromatography with a micellar cleanup and reversed-phase cliromatography , Awa/. Chem. 60 1953-1958(1988). 

J. V. Posluszny, R. Weinherger and E. Woolf, Optimization of multidimensional Mgh-perfomiance liquid clnomatography for the determination of drugs in plasma by direct injection, micellar cleanup and photodiode array detection , ]. Chromatogr. 507 267 - 276(1990). 

The interfacial activity is determined by the sterical properties of the molecule. At the interface the spatial demand A0 of the hydrophobic part of the molecule is higher because of the second chain of the internal sulfonate compared with the terminal sulfonate. Thus, the surface concentration of the surfactant molecules is lower. That means that the hydrocarbon chains are laterally oriented and therefore cover the interface between the solution surface and air more completely. Because the ratio of the spatial demand of the head group to the volume of the alkyl chain governs the radius of the micellar surface, it... 

In recent years micellar solutions of sodium dodecyl sulfate are being used increasingly in analytical determinations, chemical reactions, and catalysis. 

The effects of pH on electrokinetic velocities in micellar electrokinetic chromatography was studied by using sodium dodecyl sulfate solutions [179]. Micellar electrokinetic capillary chromatography with a sodium dodecyl sulfate pseudostationary phase has been used to determine the partition constants for nitrophenols, thiazolylazo dyes, and metal chelate compounds [180]. A similar technique was used to separate hydroquinone and some of its ether derivatives. This analysis is suitable for the determination of hydroquinone in skin-toning creams [181]. The ingredients of antipyretic analgesic preparations have also been determined by this technique [182], The addition of sodium dodecyl sulfate improves the peak shapes and resolution in chiral separations by micellar electrokinetic chromatography [183]. 

Micellar HPLC with micellar mobile phases containing sodium dodecyl sulfate, with and without different alcohols, has been used to determine diuretics in pharmaceuticals [185]. 

Watanabe, T. et al.. Separation and determination of monascus yellow pigments for food by micellar electrokinetic chromatography. Anal. Sci.,13, 571, 1997. 

Chou, S.S. et al., Determination of synthetic colors in soft drinks and confectioneries by micellar electrokinetic capillary chromatography, J Food ScL, 67, 1314, 2002. 

Thompson, C.O. and Trenerry, V.C., Determination of synthetic colours in confectionery by micellar electrokinetic capillary chromatography, J. Chromatogr. A, 704, 195, 1995. 

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