Anionic Microemulsions Research Articles

Wäßrige und nichtwäßrige Mikroemulsionen/ Aqaueous and Non-Aqueous Microemulsions

The aim of our work was to test the influence of the non-aqueous liquids formamid, ethyleneglycol, 1,2-propyleneglycol, 1,3-butyleneglycol and glycerol and the influence of anionic, cationic and non-ionic surfactants on the phase region of the microemulsions. In the triangle diagrams the existence regions of the anionic microemulsions with sodium dodecyl sulfate become larger by use of non-aqueous liquids formamid, ethyleneglycol, 1,2-propyleneglycol and glycerol in combination with p-xylene and n-pentanol

Squalene epoxide cyclase and microemulsion

Squalene epoxide cyclase was extracted from microsomal preparations of rat liver using anionic, cationic and non-ionic microemulsions. The anionic microemulsion was the best with respect to protein solubilisation, extracted cyclase activity and stability of this activity over time. The activity assay showed cyclase activity to be higher in anionic microemulsion than in buffer in the presence of surfactant. Calcium chloride in the anionic microemulsion had a stabilising effect and less total protein seemed to be extracted.

Model for microemulsions: III. Interfacial tension and droplet size correlation with phase behavior of mixed surfactants

We have developed a model for microemulsions which relates surfactant structure to microemulsion droplet size, interracial tension, and phase behavior. The concept of curvature parameter, developed to describe microemulsion phase behavior (M. L. Robbins and J. Bock, J. Colloid Interface Sci. 124, 462 (1988)), is expanded to cover interfacial tension, droplet size, and phase behavior correlations. The curvature parameter is made up of contributions from the thickness and volumes of surfactant polar heads and hydrocarbon chains at the water/oil interface. A set of equations is developed interrelating water and oil uptakes, droplet interfacial tensions, and droplet sizes via the curvature parameter and applied to equilibrated microemulsions prepared with mixtures of ethoxylated dinonyl phenol and the monoethanol amine salt of dodecyl o-xylene sulfonic acid in 1 1 decane/aqueous NaCl of varying salinity. The model predicts that droplet interfacial tensions should vary inversely with water and oil uptakes and that the square root of droplet tensions should vary linearly with the curvature parameters. Curvature parameters calculated from water and oil uptakes were found to plot linearly against salinity (see previous reference), suggesting that the square root of interracial tension should also plot linearly against salinity. Measured bulk interfacial tensions when plotted as √γ vs salinity gave linear plots as opposed to the conventional semilogarithmic plots which are highly curved. Measured bulk interfacial tensions varied inversely with water and oil uptakes and correlated very well with calculated droplet interfacial tensions using a sifigle empirical constant. Based on limited data, this constant appears to be universal for the systems tested. The current paper extends testing of theoretical correlations to include microemulsion droplet size. Droplet sizes in lower- (water-continuous) and upper- (oil-continuous) phase anionic microemulsions were measured as a function of aqueous salinity using dynamic (laser) light scattering on microemulsions prepared with the surfactant combination of monoethanol ammonium dodecyl ortho-xylene sulfonate/tertiary amyl alcohol (C 12 ∗XS-MEA/TAA) in 1 1 oil/aqueous NaC1. The model predicts that micro-emulsion droplet size should be inversely proportional to the square root of the interfacial tension (√γ), which is in turn inversely related to water and oil uptakes ( V w V s and V o V s . The value of the proportionality constant depends on the thickness and compressibility of the surfactant layer at the water/oil interface. Using the length of the C 12 ∗XS-MEA molecule measured from molecular model projections, droplet sizes calculated from water and oil uptakes agree very well with those determined by dynamic light scattering experiments, lending further support to the model.

Some observations on the effect of pressure on a five-component anionic microemulsion

Etude de l'influence de la pression sur une microemulsion du type: solution saline (NaCl)/cyclohexane/dodecylsulfate de sodium/butanol-1

Enzymes and microemulsions. Activity and kinetic properties of liver alcohol dehydrogenase in ionic water-in-oil microemulsions.

The activity and the kinetic properties of horse liver alcohol dehydrogenase have been studied in water-in-oil microemulsions containing sodium dodecyl sulfate (SDS) or hexadecyl trimethylammonium bromide (CTAB), 1-butanol or 1-pentanol or 1-hexanol or t-butanol, water and cyclohexane alone or with octane. In the anionic microemulsions (i.e. containing sodium dodecyl sulfate), the enzyme quickly lost its activity, but was efficiently protected by the coenzyme and some adenine nucleotides. In the cationic microemulsions (i.e. containing hexadecyl trimethylammonium bromide), the enzyme activity was more stable and with higher alcohols was stable for at least 20 min. The Michaelis constant of NAD+ calculated with respect to the water content was nearly constant and higher than in water. The maximum velocity in anionic microemulsions depends on the water content whereas in cationic microemulsions, the maximum velocity did not show a clear dependence on the water content and was close to the maximum velocity found in water. The pH dependence of Km and Vmax in these microemulsions was similar to that observed in water. The kinetic data for a hydrophobic substrate, cinnamyl alcohol, showed that this alcohol partitions between the pseudo-phases and thus the apparent Michaelis constant and the concentration at which substrate-excess inhibition appeared were increased. The catalytic properties of the enzyme in microemulsions were illustrated by the preparative reduction of cinnamaldehyde with cofactor recycling. The rate determination of NAD+ reduction and of 1-butanol/cinnamaldehyde redox reaction showed that at low water content (2.8%), the NAD+ reduction rate was close to zero whereas the redox reaction rate was about half of the rate at higher water content. Probably at low water content the coenzyme binding-dissociation rates are reduced much more than the binding-dissociation rates of the substrates and the rates of the ternary complex interconversion. The cationic microemulsions seemed to be very favorable medium for enzyme activity, the tetraalkyl ammonium surfactant causing less denaturation than the anionic detergent dodecyl sulfate.

Cholesterol oxidase in microemulsion: Enzymatic activity on a substrate of low water solubility and inactivation by hydrogen peroxide

Cholesterol oxidase from Nocardia erythropolis, Pseudomonas, and Streptomyces species was active in microemulsion in which cholesterol is well solubilized. The activity was stable in nonionic microemulsions whereas in cationic and anionic microemulsions the activity decreased with time. The coupled activity test using horseradish peroxidase which is very stable in microemulsion, was modified. The activity at very low water concentration in nonionic microemulsions increased with the water content. The kinetic constants were determined: the Michaelis constant is in the range 10 to 28 m m in the microemulsions, compared to 10 to 28 μ m in buffer. The maximum velocity was reduced by a factor of 3 to 5 compared to that in buffer. Neither substrate excess nor product inhibition was detected. The preparative oxidation of cholesterol revealed the inactivation of the cholesterol oxidase by hydrogen peroxide. In contrast to glucose oxidase, hydrogen peroxide inactivated cholesterol oxidase in the absence of substrate. Catalase provides protection during the cholesterol oxidation. Microemulsions are very good media in which to perform enzyme catalyzed reactions with substrates of low water solubility. Their use for the reproducible determination of cholesterol should be examined.

サスペンション及びエマルションに関する研究 ＬＸＸＸ 高分子マイクロエマルションからの陽極酸化アルミニウム板上への化学析出

サスペンション及びエマルションに関する研究 ＬＸＸＸ 高分子マイクロエマルションからの陽極酸化アルミニウム板上への化学析出

Dimer cation formation in anionic microemulsion media. Duroquinone-sensitized photooxidation of 2,6-dimethylnaphthalene and tetrathiafulvalene

Dimer cation formation in anionic microemulsion media. Duroquinone-sensitized photooxidation of 2,6-dimethylnaphthalene and tetrathiafulvalene