非离子表面活性剂Tween-20胶束体系流体室温燐光法测定色氨酸

提出了一种以非离子表面活性剂Tween 2 0为胶束介质、I-作重原子微扰剂、Na2 SO3 为除氧剂的胶束增稳室温光测定色氨酸的方法。详细研究了各种实验条件的影响。线性范围 8.0× 1 0 -8～ 8.0× 1 0 -6mol L ,检出限达 1 .4×1 0 -9mol L。直接用于大米、花生、大豆及竹笋中色氨酸的测定 ,相对标准偏差2 4%～ 3.3% ,与荧光法比较 ,相对误差 - 3.1 %～ 4.2 %。     

Study on osmotic pressure of non-ionic and ionic surfactant solutions in the micellar and microemulsion regions

To investigate the osmotic pressure of non-ionic and ionic surfactant solutions in the micellar and microemulsion regions, a potential of mean force including hard-core repulsion, van der Waals attraction and electric double layer repulsion is proposed to describe the interactions between micelles and between microemulsions. Both van der Waals attraction and electric double layer repulsion are represented using Yukawa tails. The explicit analytical expression of osmotic pressure derived from the first-order mean spherical approximation is implemented by accounting for the Donnan membrane effect. The proposed theory has been applied to micelle solutions of the non-ionic surfactant, n-dodecyl hexaoxyethylene monoether, the cationic surfactant, cetylpyridinium chloride, the anionic surfactant, sodium dodecyl sulfate, and spherical oil-in-water microemulsion system. Successful comparison is made between the proposed theory and the experimental osmotic pressure data for the studied surfactant solutions. Theoretical results show that the long-range electric double layer repulsion dramatically influences the osmotic pressure of both cationic and anionic surfactant solutions in the micellar region. The regressed model parameters such as effective micelle diameter, the mean aggregation number and effective micellar charge are in good agreement with those from static light scattering studies in the literature.     

Phase separation in non-ionic surfactant Triton X-100 solutions in the presence of phenol

The influence of concentration conditions and acidity on the phase separation in non-ionic surfactants Triton X-100 solutions in the presence of phenol was investigated. It was shown that the addition of small amounts of phenol results in the decrease of the cloud point temperature of Triton X-100 solutions. On the other hand, the addition of phenol into the investigated system resulted in the decrease of the hydration values of surfactant-rich phases and the increase of their hydrophobicity. The extraction degree and distribution coefficient of phenol between the water and the surfactant-rich phases were studied. On the basis of data obtained the molar parts of water, phenol and Triton X-100 in the non-ionic surfactant-rich phases formed at different concentration conditions were calculated. Possibilities of the application of phenol-induced micellar extraction for microcomponents preconcentration were estimated.     

Determination of antihyperglycemic drugs in nanomolar concentration levels by micellar electrokinetic chromatography with non-ionic surfactant

A method for the separation of six selected antihyperglycemic (antidiabetic) drugs (tolbutamide, gliclazide, glimepiride, glibenclamide, repaglinide, and glipizide) was developed with use of micellar electrokinetic chromatography. Two non-ionic poly(ethylene glycol)-based surfactants Genapol X-080 and Triton X-114 (reduced) were studied as neutral pseudostationary phases. High alkaline pH 10.0 was used to obtain negative charges of separated antidiabetic drugs and non-ionic surfactants were employed for selectivity alteration. Both non-ionic surfactants provided good selectivity at concentration 0.2% (v/v) in sodium borate buffer and the separation of six drugs was obtained within 5 min. An on-line preconcentration method based on reversed electrode polarity switching was employed for the determination of antihyperglycemic drugs in blood serum after acetonitrile protein precipitation. The limits of detection ranged from 20.8 nmol L⁻¹ for tolbutamide to 6.5 nmol L⁻¹ for glibenclamide, respectively.     

Fluorometric determination of uranium and tungsten with o-hydroxyhydroquinonephthalein in the presence of non-ionic surfactant

Complex formation between uranium or tungsten and o-hydroxyhydroquinonephthalein (Qnph) in various micellar surfactant media has been investigated fluorometrically, and determination of uranium and tungsten based on the difference between the relative fluorescence intensities of Qnph and the metal complex at 535 nm, with excitation at 400 nm in the presence of poly(vinyl) alcohol as a non-ionic surfactant. The calibration curves were linear up to 1.0 mu/ml uranium and 0.9, mu/ml tungsten. The relative standard deviations (5 replicates) were 2.6% for tungsten and 3.0% for uranium, and recovery tests gave relatively good results (97-104%).     

Electrochemical behavior of anthraquinone in aqueous solution in presence of a non-ionic surfactant

Cyclic voltammetric behavior of anthraquinone in aqueous medium has been studied in presence of a non-ionic surfactant, Triton X-100 (TX-100) using sodium salt of anthraquinone-2-sulphonic acid (AQS) as the electro-active species. When cathodic potential is applied, the anthraquinone (AQ) group of AQS is reduced to its dianion. In the reverse scan, the oxidation of AQ²⁻ gives AQ. The electrochemical behavior shows a profound influence from the dissolved state of TX-100 in aqueous media. Spectrophotometric results indicate interaction between AQ and TX-100. A CEC (chemical–electrochemical–chemical) mechanism with the electrochemical reaction coupled with preceding interaction of AQS with TX-100 and following protonation reaction of reduced AQ has been proposed.     

Spectrophotometric determination of tungsten based on molybdotungsten isopolyanions in presence of non-ionic surfactant

Simple and sensitive method was developed for the spectrophotometric determination of tungsten. The method was based on the formation of the colour associate of molybdotungsten isopolyanion (IPA) with organic dye malachite green and solubilization in the solution of non-ionic surface-active substance (SAS). Recommended procedure permits tungsten determination in the linear range 10⁻⁶ to 10⁻⁵ mol l⁻¹ with ε=7.1×10⁴ mol⁻¹ l cm⁻¹. More than 100-fold excess of molybdenum do not interfere. The proposed method was applied to the determination of tungsten in cobalt-molybdenum catalyst and in stainless steel with satisfactory results.     

Electrochemical nitration of naphthalene in the presence of nitrite ion in aqueous non-ionic surfactant solutions

The nitration of naphthalene (NapH) at a Pt electrode in aqueous NaNO₂ solutions both in the absence and presence of a non-ionic surfactant, Brij®35 (polyoxyethylene (23) dodecanol), has been studied. The electrochemical behaviour of the reactants NapH and NaNO₂ and a mixture of the two was investigated by cyclic voltammetry (CV) to determine the optimal electrolysis conditions. The peak current of NapH decreases with increasing NaNO₂ concentration, indicating that the oxidation product of the NO₂⁻ ion interacts with the NapH radical cation (NapH⁺). Controlled potential electrolysis (CPE) was carried out and the products were analysed by HPLC. The main products detected in the micellar medium were 1-nitronaphthalene, 2-nitronaphthalene, 1,2-naphthoquinone, and 1,4-naphthoquinone. In the absence of Brij 35, the naphthoquinones were produced but no nitration products were obtained. In both cases, unknown products are inferred by mass balance, which are believed to be derived from the oxidation of 1,1′-binaphthyl (BinapH) formed by NapH⁺ coupling in both micellar and aqueous media. A mechanism of nitration by the attack of NO₂ to NapH⁺ is proposed. The higher selectivity for formation of 2-nitronaphthalene in comparison to non-aqueous homogeneous media is attributed to the effect of the micellar microenvironment.     

Kinetic- and catalytic-spectrophotometric determination of iron by pyrogallolphthalein and potassium perdisulphate in non-ionic surfactant micellar medium

Summary A simple and highly sensitive spectrophotometric determination of iron with pyrogallolphthalein in a micellar medium of non-ionic surfactant is proposed. This method is based on the kinetic-catalytic action of iron(III) upon the decomposition reaction between pyrogallolphthalein and potassium perdisulphate at pH 2.4–2.9 in the presence of Triton X 100 as a non-ionic surfactant. The calibration graph is linear over the range 10–600 ng iron(III) per 10 ml in spectrophotometry (apparent molar absorption coefficient for decomposition was 1.25×10^–6 l per mole per cm at 385 nm). The method was applied to assay and recovery tests for artificial waste water with satisfactory results (recovery 97.6%–103.5%).

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Kinetische und katalytisch-spektralphotometrische Eisenbestimmung mit Hilfe von Pyrogallolphthalein und Kaliumperdisulfat in Gegenwart eines nichtionischen Tensids

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Application of xanthene derivatives in analytical chemistry. Part LXXV. Part LXXIV see ref. [1]     

Temperature dependence of the non-Newtonian viscosity of elongated micellar solutions

We report in this work new results of the study on the non-Newtonian viscosity of aqueous micellar solutions of cetyltrimethylammonium bromide (CTAB) in the presence of potassium bromide (KBr), in the concentration range where the elongated micelles overlap. The experiments have been performed as a function of the surfactant concentration, temperature and shear rate by use of a Couette-viscosimeter.In the non-Newtonian range, at relatively low surfactant concentration (0.25 M/l), our results show that the flow curves obtained at different temperatures converge to a single liner curve with a characteristic slope varying with the surfactant concentration. These same data can be superposed on a master curve when appropriate reduced variables are used. The shape of the flow curves obtained at different temperatures for a sufficiently high surfactant concentration is similar to that obtained for monodisperse polymer solutions at different molecular weights. The slope obtained of about –1 is also predicted by Graessley's model in the theory of microviscoelasticity based on the concept of entanglement for polymer solutions. However, at surfactant concentration higher than 0.25 M/l our results show an unusual behavior. Above some critical shear rate it is possible to obtain an increase of the apparent viscosity with temperature. One possible explanation of this effect can be found in the increase of the entanglement with concentration coupled with the temperature and direct now effects on scission and recombination rate of the micelles.     

Temperature dependence of the thermodynamics and kinetics of micellar solutions

We predict theoretically the thermodynamics and relaxation kinetics of solutions of cylindrical branched micelles. Using a recently developed theory in combination with the experimental data, we explain the unusual, inverted temperature dependence of the phase separation observed in wormlike micelles and dilute microemulsions. We extend the model to treat the temperature dependence of the relaxation kinetics and explain the observations.     

Controlling the properties of HDPE in the presence of low-molecular-mass additives of various types

To develop materials with new mechanical and improved rheological properties on the basis of common polyolefins, ultrahigh-molecular-weight PE and HDPE of medium molecular masses, the polymers have been modified with low-molecular-mass additives: crystalline organic disulfides (dithiaalkanes), liquid oligomer phenylmethylsiloxane, and oligooxypropylene glycol. It has been shown that the studied disulfide additives at low concentrations (up to 10% of the mass of PE) have no significant effect on the content and quality of the crystalline phase of HDPE. (The degree of crystallinity, enthalpy, and melting temperature change weakly.) In this case the plasticity of the modified PE improves: the tensile modulus and dynamic modulus decrease, whereas the elongation at break increases. In the presence of organic disulfides, the effective viscosity of the PE melt decreases. Unlike oligomeric phenylmethylsiloxane and oligooxypropylene glycol, dithiaalkanes are inert to the components of metallocomplex catalysts. Thus, the modification of PE with the aforementioned additives may be performed via their addition to the final polymer or in the course of the synthesis of the polymer.     

Temperature dependence of viscosity for sucrose laurate/water micellar systems

The viscous behavior of sucrose laurate aqueous systems of high hydrophilic-lipophilic balance up to a 50% (wt) surfactant concentration at temperatures between 5°C and 60°C has been studied. Systems up to a 45% (wt) surfactant concentration show Newtonian behavior. The influence of temperature was studied using the activated diffusive relaxation model described by Goodwin. A maximum specific viscosity that appears at lower temperature as sucrose laurate concentration increases can be observed. These results are related to the micellar growth of the sucrose laurate aggregates as temperature rises. More concentrated systems show complex viscous response. Thus, a limit viscosity at low shear rates and a shear-thinning behavior after a critical shear rate are observed. Limit viscosity decreases and critical shear rate increases as temperature rises. This behavior is related to the threshold micelle concentration for entanglement of rod-like micelles.Nomenclature A Parameter of the equation that relatesE and temperature - B Pre-exponential factor of the Arrhenius equation - C Sucrose ester concentration (kg · m^–3) - CMC Critical micelle concentration - E Activation energy for long-range diffusive motion (Goodwin model) - E _a Activation energy of the viscous flow (Arrhenius equation) - E ₀ Parameter of the equation that relatesE and temperature - HLB Hydrophilic/lipophilic balance of the sucrose ester - J Constant that depends on the aqueous phase viscosity and mean micellar radius - k Boltzmann's constant - k ₁ Parameter of the Goodwin equation - k ₂ Parameter of the Goodwin equation - q _rel Contribution of the hydrodynamic interactions - R _e External radius of the sensor system - R _i Inner radius of the sensor system - T Temperature - T _max Temperature at the maximum viscosity - Newtonian viscosity - _i Intrinsic viscosity - _rel Relative viscosity = _solution/_water - _red Reduced viscosity = _sp/C - _sp Specific viscosity = _rel – 1 - ₀ Zero-shear-rate viscosity     

Spectrophotometric and derivative spectrophotometric determination of palladium(II) using pyridopyridazine dithione in the presence of non-ionic surfactant

Pyridopyridazine dithione (PPD) was synthesized as a new sensitive and selective reagent for spectrophotometric and derivative spectrophotometric determination of palladium(II). In aqueous and micellar medium, PPD forms 1:4 complexes having molar absorptivities of 4.68 × 10⁴ and 5.74 × 10⁴lmol^–1 cm^–1 at 570 and 615 nm, respectively. Beer's law was obeyed up to 2.2 and 2.5 g ml^–1 with detection limits of 0.2 and 0.1g ml^–1. The relative standard deviations for 1.23g ml^–1 were 2.6 and 1.3%, in the absence and presence of Triton X-100. In fourth-derivative mode, the regression equation, linear range, detection limit and RSD for 0.075 g ml^–1 wereD ₄ = 4.3C + 1.5 × 10^–3, 0.013 – 0.23 g ml^–1, 3.7 ng ml–1 and 0.78%, respectively. The ionization constants of the reagent and stability constants of the complexes were evaluated. The method is free from interference by most common metal ions and anions. The method was applied for determination of palladium in activated charcoal.     

Second CMC in surfactant micellar systems

Experimental reports of surfactant systems displaying a second critical micelle concentration (second CMC) have been surveyed. It turns out that surfactant micelles usually show a growth behavior with some typical features. (i) Micelles grow weakly at low surfactant concentrations but may switch to a much stronger growth behavior at higher concentrations. The second CMC is defined as the point of transition from weakly to strongly growing micelles. (ii) Micelles are found to be non-spherically shaped below the second CMC. (iii) At the second CMC micelles are found to be much smaller, with aggregation numbers typically 100–200, than expected for flexible micelles. (iv) Micelles of intermediate size are present in a narrow concentration regime close to the second CMC. (v) Micelles grow much stronger above the second CMC than expected from a sphere-to-rod transition. The conventional spherocylindrical micelle model predicts a smooth growth behavior that contradicts the appearance of a second CMC. Modifying the model by means of including swollen end caps neither account for the presence of micelles with intermediate size, nor the strong growth behavior above the second CMC. Taking into account micelle flexibility is not consistent with the rather low micelle aggregation numbers observed at the second CMC. On the other hand, a recently proposed alternative theoretical approach, the general micelle model, have been demonstrated to take into account basically all features that are typical of experimentally observed micellar growth behaviors.     

On the theory of surfactant mobility in micellar systems

Specific features of surfactant diffusion in micellar systems are described in terms of mobility, i.e., the limiting velocity of a particle under the action of a unit force. Micellar solutions of nonionic and ionic surfactants are analyzed. A relation is established between average surfactant mobility and the mobilities of individual particles. Although micelles have a lower mobility than monomers have, the average mobility of surfactants is shown to increase rather than decrease upon micellization. In parallel, formulas describing diffusion coefficients are derived, with part of the formulas having been available in the literature.     

Microwave-enhanced electrochemical processes in micellar surfactant media

High intensity microwave radiation effects are demonstrated for electron transfer processes at 25 or 50-μm diameter platinum electrodes immersed in micellar sodium dodecylsulfate (SDS) solutions. First, a solution containing 2 mM Fe(CN)₆³⁻ and 2 mM Fe(CN)₆⁴⁻ in aqueous 0.1 M NaCl with and without SDS is employed to calibrate the electrode temperature and mass transport conditions. Addition of 0.1 M SDS has only a small effect on the microwave enhanced voltammetry for the Fe(CN)₆^3-/4− system. Next, two highly water-insoluble redox systems are studied. A solution of 1 mM tert-butylferrocene in aqueous 0.1 M NaCl containing 0.1 M SDS is shown to give no current response in the absence of microwaves. In the presence of focused microwaves at a platinum disc electrode, a strong current for the one electron oxidation of tert-butylferrocene is detected presumably due to localized disruption of the micellar solution. Concentrations of tert-butylferrocene down to the micromolar level are detected. α-Tocopherol, a lipophilic vitamin and antioxidant, is soluble in aqueous 0.1 M SDS/0.1 M NaCl. In the presence of microwave radiation, a strong and concentration dependent anodic current response consistent with the two-electron oxidation of α-tocopherol is observed. A heptode array of seven individual 50 μm diameter platinum microelectrodes placed in ca. 720 μm distance of each other is shown to allow microwave enhanced currents to be increased sevenfold with each electrode exhibiting the same microwave effect.     

Salting-out surfactant extraction of porphyrins and metalloporphyrin from aqueous non-ionic surfactant solutions

A number of cloud point temperature-depressing electrolytes have been investigated for the separation of a non-ionic surfactant (Triton X-100) from aqueous solutions and the corresponding extraction of the organic solutes into the smaller volume surfactant-rich phase using the salting-out method. High extraction efficiencies and preconcentration factors were obtained at room temperature for the extraction of several hydrophilic and hydrophobic metal-free porphyrins (uroporphyrin, coproporphyrin, protoporphyrin and hematoporphyrin) and one metalloporphyrin (iron-protoporphyrin) that were dissolved in the aqueous non-ionic surfactant solutions. Possible mechanisms responsible for the efficient extraction of these important biological molecules into the surfactant-rich layer are discussed.     

The interaction of electrolytes with non-ionic surfactant micelles

The effect of NaCl and HCl on two non-ionic surfactant micelles was studied using several techniques, including conductivity and ion-selective electrodes. Both surfactants exhibit opposite behaviour. When Tween 20 is titrated with HCl the conductivity notably increases in comparison with water, whereas that of Triton X-100 solutions do not change with respect to water until a certain HCl concentration is reached, when it increases. The hydrogen ion activity is lower in Triton X-100 solutions and higher in Tween 20 solutions than in pure water. Chloride ion activity is higher in Tween 20 solutions than in water, whereas in Triton X-100 the activity does not significantly differ from that in water. The activity of sodium ion is lower in Tween 20 solutions than in water, whereas that in Triton X-100 solutions does not differ from the titration of water. These phenomena are explained by the changes in conformation of the non-ionic headgroups, which capture water, and in some cases ions, modifying the activity of ions in the intermicellar solution.