Volume and heat capacity of model non-aqueous self-assembly systems

Blends of immiscible polymers are often stabilized by block copolymers which can form non-aqueous micelles and microemulsions in the liquid polymers. The phase diagrans, apparent volumes and apparent heat capacities of model non-aqueous binary and ternary systems were studied in order to investigate the conditions under which such self-assembly systems could form. 1,2-Hexanediol, which can cosolubilize hexane and ethyleneglycol, forms inverse micelles in hexane and weak microaggregates in ethyleneglycol. Genapol X-060, a commercial alcoholic surfactant containing on the average an aliphatic chain of 13 carbons and 6 oxyethylenes (C₁₃E₆), forms microaggregates in poly(ethyleneglycol) 400. These self-assembly systems are strengthen in the presence of a third component which has an affinity for the inner phase.Presented at the Symposium, 76^th CSC Congress, Sherbrooke, Quebec, May 30–June 3, 1993, honoring Professor Donald Patterson on the occasion of his 65^th birthday.     

The effect of H2S concentration on the corrosion behavior of API 5L X-70 steel

This work presents electrochemical data measured during the corrosion of API 5L X-70 pipeline steel immersed in aqueous environments containing dissolved H₂S. Three different electrolyte were used: a 3 wt% NaCl solution containing 100, 650 and 2,550 ppm of H₂S respectively. The corrosion of steel is described by means of electrochemical impedance spectroscopy. The electrochemical data obtained from the steel monitoring are presented in terms of Nyquist plots. The influence of the total H₂S concentration as well as the effect of temperature on the corrosion of API 5L X-70 steel were also studied. In the presence of H₂S the R_ct values decrease as the H₂S concentration increases.     

Hydrolysis of cephanone in the micelles with different charges

The hydrolysis of cephanone in water and micelles with different charges was studied by UV-vis absorption spectroscopy. The change of pH with the hydrolysis of cephanone was determined. The mechanism of the hydrolysis and the effect of the acidity of the media on the hydrolysis were studied. The results show that the hydrolysis rate of cephanone increases with the acidity. Compared with water, SDS micelles accelerate this hydrolysis, whereas CTAB and Triton X-100 micelles suppress it. The effects of the micelles with different charges on the hydrolysis are explained by the proton concentration of the micro-environment where cephanone exists and by the charge density of the polar group of the cephanone molecules.     

利用Triton X-100合成介孔二氧化硅及其形貌研究

以非离子型表面活性剂Triton X-100为模板剂,正硅酸乙酯为硅源,合成了介孔二氧化硅分子筛.利用XRD、N2吸附—脱附、SEM、以及TG-DTA对样品进行了表征,结果表明合成的材料具有有序介孔结构、高比表面积及高孔容。同时比较了不同条件下所得产物的形貌结构,并分析了它们的形成机理。     

Determination of Utratrace Silver Using Surfactant As Sensitizer by Catalytic Near Field Laser Thermal Lens Spectrometry

Thermal lens spectrometry (TLS) is an excellent tool for trace analysis1. TLS allows the detection of absorbances of 10-7～10-8, concentration of ≈ 10-11 mol稬-1 and the analysis of 10-15 L volumes with ≈10-2 absorbing molecules2. Kinetic analysis is playing an increasingly important part in modern analytical chemistry. Therefore, TLS shows much promise in combination with kinetic analysis. However, there are few data on TLS applications in kinetic analysis method so far3～4. A ne…     

Kinetics of the surface tension of micellar solutions: Comparison of different experimental techniques

The kinetics of the surface tension of micellar solutions of nonionic surfactant Triton X-100 is measured experimentally by means of three different techniques: oscillating jet, maximum bubble pressure and inclined plate. They allow to study the micellization kinetics at various time scales (from a few milliseconds to a few seconds) in fairly large concentration region up to 50 times CMC. The experimental data are satisfactorily explained by a theoretical model accounting for the kinetics of micellization, diffusion of surfactant species and expansion of the bubble interface. By this model are computed the characteristic times of diffusion and micellization, which are of comparable magnitude (about 5 to 200 ms), and the Gibbs' elasticity. The micellization time constant corresponds to the slow relaxation process known to coincide with the disintegration of micelles. Comparing our data with other data from literature one can conclude that more realistic information for the micellization kinetics is obtained by the maximum bubble pressure and the oscillating jet method. The inclined plate seems too slow to measure the relaxation processes in micellar solutions of this surfactant.     

Determination of pyrithione in natural waters by cathodic stripping voltammetry

A method was developed to determine the biocide pyrithione in natural waters. The method is based on cathodic stripping voltammetry (CSV) in the presence of Triton-X-100, which is used to separate the peak from interfering thiol compounds. Optimised conditions include a Triton-X-100 concentration of 4 ppm and a pH adjusted to 9 using ammonia buffer. The adsorption potential for pyrithione was −0.10 V and the peak occurred at −0.2 to −0.3 V. Detection was by differential-pulse CSV. The detection limit in UV-digested seawater was 1.5 nM for a deposition time of 60 s. In principle, this limit of detection could be lowered by extending the adsorption time, but in practice this may not be possible due to interferences by other organic compounds (surfactants and thiol compounds) in natural waters.     

Reduction of soluble colloidal MnO<Subscript>2</Subscript> by <Emphasis Type="SmallCaps">DL</Emphasis>-malic acid in the absence and presence of nonionic TritonX-100

Kinetics of oxidation of DL-malic acid by water soluble colloidal MnO₂ (prepared from potassium permanganate and sodium thiosulfate solutions) have been studied spectrophotometrically in the absence and presence of nonionic Triton X-100 surfactant. The reaction is autocatalytic and manganese(II) (reduction product of the colloidal MnO₂) may be the autocatalyst. The order of the reaction is first in colloidal [MnO₂] as well as in [malic acid] both in the absence and presence of the surfactant. The reaction has acid-dependent and acid-independent paths and, in the former case, the order is fractional in [H⁺]. The effect of externally added manganese(II) is complex. The results show that the rate constant increases as the manganese(II) concentration is increased. It is not possible to predict the exact dependence of the rate constants on manganese(II) concentration, which has a series of reactions with other reactants. In the presence of TX-100, the observed effect on k is catalytic up to a certain [TX-100]; thereafter, an inhibitory effect follows. The catalytic effect is explained in terms of the mathematical model proposed by Tuncay et al. (in Colloids Surf A Physicochem Eng Aspects 149:279 3). Activation parameters associated with the observed rate constants (k_obs/k) have also been evaluated and discussed.     

Cloud point extraction equilibrium of lanthanum(III), europium(III) and lutetium(III) using di(2-ethylhexyl)phosphoric acid and Triton X-100

The cloud point extraction behaviors of lanthanoids(III) (Ln(III) = La(III), Eu(III) and Lu(III)) with and without di(2-ethylhexyl)phosphoric acid (HDEHP) using Triton X-100 were investigated. It was suggested that the extraction of Ln(III) into the surfactant-rich phase without added chelating agent was caused by the impurities contained in Triton X-100. The extraction percentage more than 91% for all Ln(III) metals was obtained using 3.0 × 10⁻⁵ mol dm⁻³ HDEHP and 2.0% (v/v) Triton X-100. From the equilibrium analysis, it was clarified that Ln(III) was extracted as Ln(DEHP)₃ into the surfactant-rich phase. The extraction constant of Ln(III) with HDEHP and 2.0% (v/v) Triton X-100 were also obtained.     

Dialysis-Chelex method for determination of exchangeable copper in human plasma

A method based on dialysis in the presence of histidine, and subsequent copper adsorption and preconcentration using Chelex-100 resin, has been developed for selective extraction of exchangeable copper from blood plasma. The method was verified by comparative analysis using two different instrumental techniques, ICP–MS and AAS. The results obtained were in excellent agreement. Accurate quantification of the exchangeable copper and the firmly bound copper was achieved. The method was further validated by analysis of a lyophilised human serum certified reference material.