Micellar Solutions Of Anionic Surfactants Research Articles

ПРОТОЛІТИЧНІ РІВНОВАГИ3-(ТРИФЛУОРОАЦЕТИЛ)ІМІДАЗО[1,2-a]ПІРИМІДИНУ В МІЦЕЛЯРНИХ РОЗЧИНАХ АНІОННОЇ ТА ЦВІТЕР-ІОННОЇ ПАР

Мета роботи. Дослідження протолітичних властивостей та спектральних характеристик протигрибкової субстанції 3-(трифлуороацетил)імідазо[1,2-a]піримідину в міцелярних розчинах аніонної та цвітер-іонної поверхнево-активних речовин.
 Матеріали та методи дослідження. У роботі використано стандартну спектрофотометричну методику з потенціометричним контролем рН водної фази.
 Результати і обговорення. У водних розчинах 3-(трифлуоро­ацетил)імідазо[1,2-a]піримідину існують дві протолітичні рівноваги: в лужних розчинах спостерігається молекулярна депротонована форма R; форма HR+ існує в діапазоні рН від 7 до 4, дикатіон H2R2+ існує у середовищі з рН < 1.
 У роботі досліджено кислотно-основні властивості та спектральні характеристики 3-(трифлуороацетил)імідазо[1,2-a]піримідину у міцелярних розчинах поверхнево-активних речовин (ПАР): аніонної ПАР – натрій н-додецилсульфаті (н-C12H25OSO3Na, ККМ ~ 8´10–3 М) та цвітер-іонної ПАР – цетилдиметиламонійпропансульфонаті (C16H33N(CH3)2(CH2)3SO3-, ККМ ~ 5´10–5 М).
 Розраховано константи ступінчастої дисоціації речовини у воді та «уявні» («apparent») константи ступінчастої дисоціації в міцелярних системах.
 Результати показали, що в міцелярних розчинах аніонної ПАР константи дисоціації збільшуються порівняно з водними розчинами через додатковий внесок електростатичної складової міцелярної поверхні, якою зв’язується субстрат. У міцелярних розчинах цвітер-іонної ПАР значення констант дисоціації досліджуваної речовини незначно змінюються порівняно з водними розчинами, що свідчить про низький розподіл речовини між водною фазою та міцелярною псевдофазою, унаслідок нейтральної поверхні міцел цвітер-іонної ПАР.
 Висновки. Досліджено кислотно-основні та спектральні характеристики вперше синтезованої субстанції 3-(трифлуороацетил)імідазо[1,2-a]піриміди­ну протигрибкової дії у воді та у міцелярних розчинах аніонної та цвітер-іонної ПАР. Розраховано константи ступінчастої дисоціації речовини у всіх досліджуваних системах.

Fluorimetric assay of flumequine using sensitized terbium fluorescence in organized media

The effects of second ligands, micellar surfactant solutions, and microemulsions on the sensitized fluorescence signal from a chelate of Tb3+ with flumequine (FL) were studied. The presence of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline in a microemulsified medium of the “oil in water” type produced a six-fold increase in the sensitized fluorescence signal from the binary chelate of Tb3+ and FL. 1,10-Phenanthroline as a second ligand and micellar solutions of anionic surfactants increased emissions by a factor of 4.4 at pH 7.0. The latter system was used to develop a fluorimetric assay for flumequine operating over the concentration range 2.6 × 10−9to 0.26 × 10−6g/ml, R 2 = 0.997, with a detection limit of 1.3 × 10−9g/ml.

Anionic Surfactant-Based Extraction of Polycyclic Aromatic Hydrocarbons from Sediment

Polycyclic aromatic hydrocarbons (PAHs) including phenathrene, fluoranthene, and pyrene in sediment were extracted with aqueous micellar solutions of anionic surfactants. The surfactants examined were sodium dodecyl sulfate, sodium oleate, and sodium di(2-ethylhexyl) sulfosuccinate. The extraction yields of PAHs increased with increasing the surfactant concentration and the extraction time. They reached constant values (ca. 30%), which agreed with results obtained by the 1-butanol extraction method. The present results suggest the usefulness of surfactant-based extraction for evaluating the bioavailability of organic pollutants in sediments.

Photolysis of 1,2-dihydroquinolines in micellar solutions of anionic and cationic surfactants

The kinetics of the photolysis of substituted 1,2-dihydroquinolines (DHQ) in micellar solutions was studied by steady-state and flash photolysis. The photolysis mechanism depends dramatically on the location of DHQ molecules in micelles, which is governed by the surfactant nature. In micellar solutions of the anionic surfactant sodium dodecyl sulfate (SDS), where the DHQ molecules are located in the Stern layer, the intermediate species decay kinetics follows a first-order law. When DHQ is in neutral form (pH 4–12), the rate constant of the intermediate carbocation decay increases from 25 to 198 s−1 with an increasing concentration of DHQ in micelles. The positive micellar catalysis is caused by the acceleration of the final product formation with the DHQ molecule via proton abstraction from the intermediate cation. The formation of several types of intermediate species—carbocations in the aqueous phase and aminyl radicals in micelles—is observed in micellar solutions of the cationic surfactant cetyltrimethylammonium bromide (CTAB) due to the preferential location of DHQ molecules in the micellar core. The carbocation decays via a pseudofirst-order reaction with a rate constant close to that in the aqueous solution. The lifetime of the DHQ aminyl radicals in the micellar solutions is longer by several orders of magnitude than the lifetime observed for homogeneous solutions of hydrocarbons and alcohols.

Fluorimetric determination of tetracyclines with the europium chelate of 1,10-phenanthroline in micellar solutions of anionic surfactants

The fluorescence of europium(III) in micellar solutions of surfactants sensitized by tetracycline derivatives was studied. It was found that the fluorescence intensity in the system Eu3+-tetracycline derivatives increases in the presence of 1,10-phenanthroline by a factor of 3–4. In micellar solutions of sodium dodecylbenzene sulfonate, the signal additionally enhances by a factor of 2.5. A procedure was developed for determining tetracycline and three its derivatives in blood plasma.

Selective counterion condensation in ionic micellar solutions

Small-angle neutron scattering experiments have been carried out on micellar solutions of cationic surfactants of cetyltrimethylammonium bromide (CTABr) and chloride (CTACl) in the presence of varying concentrations of salts KBr and KCl. In these systems, while the size of micelles strongly increases with the addition of KBr, the effect of addition of KCl in comparison is much less pronounced. It is found that in equimolar surfactant to salt micellar solutions of CTABr/KCl and CTACl/KBr, the micellar sizes are larger in CTACl/KBr than those in CTABr/KCl. The measurements have been done for different equimolar surfactant to salt concentrations and at different temperatures. We explain these results in terms of selective counterion condensation on the micelles. That is, while the condensation of Cl- counterions on the CTABr micelles in CTABr/KCl takes place around the condensed Br- counterions of CTABr, the Cl- counterions of CTACl in CTACl/KBr are replaced by Br- counterions of the salt. Similar results have also been obtained on micellar solutions of anionic surfactants of sodium dodecyl sulfate and lithium dodecyl sulfate in the presence of salts LiBr and NaBr, respectively.

Influence of the structure of amphiphilic anions on the Krafft temperature of micellar solutions of anionic surfactants

The influence of the structure of surfactants on the Krafft temperature Tk was studied for aqueous solutions of anionic surfactants containing the sulfate and sulfonate head groups, the hydrophilic (H) and lipophilic (L) fragments in amphiphilic anions, and various polar and C8—C18 hydrocarbon groups. The best statistical quality was obtained for the model with separate account of the effect of the H and L structural fragments on the Tk value.

Ordered micelle structuring in thin films formed from anionic surfactant solutions: II. Model development

We observed the phenomenon of the stratification of thinning liquid films with both micellar solutions of anionic surfactants and solutions containing latex particles. To explain this phenomenon, we suggest that the stratification is a layer-by-layer decrease of the thickness of an ordered micellar (or latex) structure inside the film. To interpret the available experimental data for stratifying films from micellar solutions of sodium dodecyl sulfate (NaDS), a simple cell model is suggested. It permits calculation of the disjoining pressure contribution which is due to the presence of micellar structure inside the film. The micelles interact via screened electrostatic repulsion forming an ordered structure due to the restricted volume of the film. The calculated excess energy per unit area of the film exhibits a number of minima corresponding to the metastable states with micellar layers inside the film. The values of the film thickness at the metastable states were predicted by the model and agreed with the experiment.