Spectrophotometric determination of sodium dodecyl sulfate with preconcentration by reversed micelles of triton N-42

Micellar preconcentration has been proposed to improve the procedure of spectrophotometric determination of sodium dodecyl sulfate (SDS). It involves quantitative extraction by reversed micelles of Triton N-42 in n-decane and the subsequent formation of an ion associate with methylene blue and azure A upon destruction of the micellar solution by diluting it with a mixture of chloroform and n-decane in the presence of small concentrations of a dye solution. The absence of losses of 10^?7?10^?5 M SDS upon from 5-to 50-fold preconcentration is confirmed by the standard addition method (RSD = 4–5%); the determination limit of SDS equals 5 × 10^?8 M.     

Kinetics of dissolution of silver nanoparticles inside triton N-42 reversed micelles

Our spectrophotometric study of the kinetics of dissolution of silver nanoparticles by nitric acid inside inverted micelles of Triton N-42 (a nonionic surfactant) verified the universal character of the mechanism for this type of process, which includes the interaction of surface metal atoms with an oxidizer in two routes: either with (autocatalysis) or without newly formed ionic species of the oxidized metal. Effective rate constants for both routes are independent of the value of solubilization capacity (V _s /V _o is the ratio of the volume of the dispersed aqueous phase to the volume of the micellar solution); the solubilization capacity is useful to control the micelle and particle sizes: k ₁ = 0.018±0.003, 0.010±0.003, and 0.012±0.003 s⁻¹ and k ₂ = 2.5±0.8, 1.5±1.1, and 1.4±0.4 L/(mol s) for 100 V _s /V _o = 1, 2, and 3%, respectively.     

Spectrofluorimetric determination of niobium with morin enhanced by cetyltrimethylammonium bromide micelles

The effect of surfactants on the fluorescence of the niobium—morin system is described. Cationic surfactants strongly enhanced the intensity (e.g., cetyltrimethylammonium bromide (CTAB) gives an 80-fold increase), while anionic and non-ionic surfactants are without effect. The formation of 1:1 and 1:3 (Nb:morin) complexes is demonstrated spectrophotometrically. The conditional stability constants for these complexes in CTAB micelles are β₁ = (1.14 ± 0.01) × 10⁴ l mol^?1 amd β₃ = (5.66 ± 0.02 × 10¹⁰ l³ mol^?3. The micellar-enhanced fluorimetric method has a 1 μg l^?1 detection limit, and is highly selective. The r.s.d. for the determination of 50 μg l^?1 Nb is 3.5%.     

Flow-injection spectrophotometric determination of molybdenum and vanadium with carminic acid in the presence of cetyltrimethylammonium bromide

The color-forming reactions of molybdenum(VI) and vanadium(IV) with carminic acid (CA) in the presence of cetyltrimethylammonium bromide (CTAB) were used in the flow-injection determination of these metals. The micellar medium enhances the spectrophotometric features of the Mo(VI)-CA and V(IV)-CA binary complexes, and the higher solubility of these complexes when the CTAB concentration is above critical micelle concentration permits the easy application of flow-injection systems. Under the optimum conditions, linear calibration graphs were obtained from 0.76 to 28.8 g/ml for molybdenum and from 0.30 to 9.1 g/ml for vanadium. The detection limits were 0.33 and 0.16 g/ml for molybdenum and vanadium, respectively. The selectivity of the method was investigated and the procedure was successfully applied to the determination of molybdenum in steels and pharmaceuticals and of vanadium in petroleum products.     

Substoichiometric determination of mercury with cetyltrimethylammonium bromide

A radiometric method based on substoichiometric isotope dilution analysis has been developed for the determination of mercury using cetyltrimethylammonium bromide (CTAB) as the substoichiometric reagent. The method is based on the extraction of mercury as an ionassociation complex of tetraiodomercurate(II) ion with a substoichiometric amount of CTAB in benzene. The calibration graph was found to be linear in the range 0–10 μg Hg (II) in the aqueous phase of 10 ml volume. A detection limit of 0.06 μg·ml⁻¹ could be achieved by the proposed method. The relative standard deviation of the method was found to be 3.0% and the method has been successfully applied to study the determination of mercury in various synthetic mixtures.     

Effect of dioctyl sulfide on the kinetics of oxidative dissolution of gold nanoparticles in triton N-42 reverse micelles

The effect of additions of hydrophobic dioctyl sulfide (L) on the kinetics of dissolution of gold nanoparticles in the interaction with a dispersed aqueous hydrochloric solution of H₂O₂ in Triton N-42 reverse micelles (decane was the dispersion medium) was studied spectrophotometrically. The process consists of a two-stage oxidation Au⁰ → AuCl₂⁻ → AuCl₄⁻ at the surface of gold particles; the first stage occurs in two ways: a spontaneous reaction and an autocatalytic reaction involving AuCl₄⁻ ions. With small additions of L (c _L < c _Au), only spontaneous oxidation of Au(0) to Au(I) takes place because Au(I) is completely bound in an inert complex AuLCl. When unbound L is exhausted, the newly formed AuLCl is accumulated in micellar shells, changes the properties of the medium inside the micelles, and affects the rate constant of the autocatalytic reaction, which increases with increasing c _L. At high concentrations of L, the coagulation of particles occurs instead of their dissolution, because of the deterioration of the protective properties of micellar shells as a result of the ingression and accumulation of dioctyl sulfide molecules on account of selective adsorption on gold particles. The rate constants of all stages of dissolution and coagulation are determined.     

用磷酸二异辛酯/正辛醇反胶束从面包酵母粗提液中萃取谷胱甘肽

采用磷酸二异辛酯（P204）/正辛醇反胶束液从面包酵母粗提液中萃取还原型谷胱甘肽(GSH),研究了各种因素对萃取率的影响以及水相pH值和P204浓度与GSH萃取率关系的数学模型。正交实验确定,GSH的最佳萃取条件是水相pH值2.0,K+浓度0.1 mol•L-1,萃取时间15 min,P204浓度0.16 mol•L-1,GSH单次的萃取率为33.1%,2次萃取率达到49.7%。     

Extraction by reversed micelles of the intrecellular enzyme xylose reductase

Applied Biochemistry and Biotechnology - Xylose reductase enzyme (EC 1.1.1.21) produced by Candidaguilliermondii in sugarcane bagasse was extracted by reversed micelles of N-benzyl-N-dodecyl-N-bis...     

The preparation of gold nanoparticles in triton N-42 reverse micelles after preliminary concentration from acid sulfate-chloride solutions

The distribution of Au(III) between an acid (3 mol/l HCl) aqueous phase and a micellar Triton N-42 solution in n-decane was studied as a function of the concentration of Na₂SO₄ (0–3.55 mol/l). The high distribution coefficients (200–500) allow 50-fold absolute concentration to be performed at a 90% extraction. Au⁰ nanoparticles were obtained by the injection solubilization of a reducing agent (hydrazine) into micellar extracts. At low solubilization capacities (≤1 vol %) and high reducing agent concentrations (≥0.2 mol/l) in Triton N-42 micelles, stable systems of Au⁰ nanoparticles suitable for the spectrophotometric determination of gold were obtained. At high solubilization capacities and low hydrazine concentrations, reduction was accompanied by coagulation and sedimentation processes. These processes were studied by spectrophotometry and the static and dynamic light scattering methods.     

Interaction of quinapril anion with cationic surfactant micelles of cetyltrimethylammonium bromide

In this study, the interaction of the anion of quinapril (QUIN), angiotensin converting enzyme (ACE) inhibitor, with cationic surfactant cetyltrimethylammonium bromide (CTAB) was investigated. The effect of cationic micelles on the spectroscopic and acid-base properties of QUIN was studied at pH 8. The binding of QUIN anion to CTAB micelles implied a shift in drug acidity constant (pK(a)(water)-pK(a)(micelle)=1.39) proving the great affinity of negatively charged QUIN ion for the positively charged CTAB micelle surface. The strong dependence of the partition coefficient K(x) on QUIN concentration, obtained by using pseudo-phase model, is consistent with an adsorption-like phenomenon. From the dependence of differential absorbance at lambda=272 nm on CTAB concentration, by using mathematical model that treats the solubilization of QUIN anion as its binding to specific sites in the micelles (Langmuir adsorption isotherm), the binding constant K(b)=(2.3+/-0.4)x10(3) mol(-1)dm(3) was obtained. QUIN-CTAB binding constant was also calculated from micellar liquid chromatography (MLC) and this method was found to be not accurate enough for its determination.     

Simultaneous electrochemical determination of three sunscreens using cetyltrimethylammonium bromide

This paper proposes a methodology based on electrochemical reduction for the simultaneous determination of three sunscreen agents, namely 4-methylbenzylidene camphor (MBC), benzophenone-3 (BENZO) and 2-ethylhexyl-4-methoxycinnamate (EHMC) by differential-pulse polarography (DPP). The highest peak currents and optimal separation of reduction peaks were obtained by using a supporting electrolyte consisted of Britton-Robinson buffer-methanol (8:2) solution at pH 4.0 and cationic surfactant 3.0 x 10(-4)mol L(-1) cetyltrimethylammonium bromide (CTAB). The methodology was validated using four commercial sunscreen preparation as a sample and the results showed high recovery rates. The efficiency of the proposed methodology was demonstrated by comparing the results obtained by DPP with those obtained by the high-performance liquid chromatography (HPLC) method.     

Properties of water in triton N-42 reverse micelles during the solubilization of HCl solutions according to FT-IR and photon correlation spectroscopy

FT-IR and photon correlation spectroscopy methods are used to study the distribution of free (bulk) and bound (hydration) water in Triton N-42 reverse micelles under the conditions of injection solubilization of hydrochloric acid solutions. The amount of each type of water is calculated depending on the solubilization capacity (V _s/V _o) and HCl concentration in the aqueous pseudophase. According to the IR spectroscopy data, the distribution of water is largely determined by the solubilization capacity of the micellar solution, while the fraction of bulk water exceeds significantly the value calculated by the geometric approach based on the photon correlation spectroscopy data. The difference shows that there is bulk water in the surface layer formed by oxyethyl groups of Triton N-42 molecules in spherocylindrical micelles.     

Control of the catalytic effect of cetyltrimethylammonium bromide micelles by the addition of background electrolyte and nonionic surfactant

The variation of the microscopic properties (surface potential, micropolarity, etc.) of the interface of cetyltrimethylammonium bromide micelles upon the addition of a background electrolyte or the nonionic surfactant Triton X-100 decreases the rates of ion-molecular reactions, namely, alkaline hydrolysis of carboxylic acid esters and tetracoordinate phosphorus acid esters, and results in the shift of acid-base equilibria. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1933–1940, October, 2007.     

Spectrophotometric determination of germanium with Catechol Violet and cetyltrimethylammonium bromide

A ternary complex between germanium, Catechol Violet (CV) and cetyltrimethylanunoniuni bromide is proposed for the determination of germanium. The stoichiometric ratio Ge:CV is 1:2. Beer's law is obeyed from 0.1 to 1.0 ppm of Ge. The method is highly selective. Interference from Sn(IV), Fe(III), Bi(III), Cr(VI), Mo(VI), V(V) and Sb(III) in mg amounts is eliminated by extracting the germanium into carbon tetrachloride from 9M HC1 and then stripping into water before the photometric determination.     

Spectrophotometric determination of thorium with Xylenol Orange and cetyltrimethylammonium bromide

The thorium-Xylenol Orange reaction sensitized by cetyltrimethylammonium bromide ( = 5.51 x 10(4) l.mole(-1).cm(-1)) is accompanied by a bathochromic shift from 570 to 600 nm. The system is more selective than the binary system, because the reaction pH is lowered from 4.0 to 2.5; Beer's law is obeyed for 0.04-4.00 ppm of thorium.     

Extraction of uranium with 2,3-dihydroxynaphthalene and cetyltrimethylammonium bromide, and its fluorimetric determination in silicate rocks

A novel procedure for the extraction of uranium has been described. UO₂ ²⁺ forms a 1:3 anionic complex with 2,3-dihydroxynaphthalene in the pH range, 4–12. This anionic complex is best extracted into ethyl acetate at pH 11–12 under the influence of a counter cation, cetyltrimethylammonium bromide. This extraction technique has been extended to the separation of uranium from silicate rock matrices for its determination by fluorimetry. Except Co, Cr, and Fe, most elements present in silicate rocks do not interfere. While the interferences of Co and Cr are suppressed by the addition of EDTA, iron is removed by prior extraction at pH 4–5 as its neutral complex with 2,3-dihydroxynaphthalene. The results compare favourably with those obtained from the conventional technique, i.e., extraction of uranium in ethyl acetate from NHO₃ medium under the influence of Al(NO₃)₃ ^.9H₂O as salting out agent. The extraction system under study is capable of separating even ultra-trace amounts of uranium quantitatively from complex matrices of rock samples. Besides, the method is simple, rapid, cost effective and precludes the use of reagents like nitric acid and aluminum nitrate (salting out agent) required in bulk quantities in the conventional system.     

Study of water properties during Pt(IV) and Au(III) extraction by triton N-42 reverse micelles from acid sulfate-chloride solutions

FT-IR spectroscopy is used to study the distribution of bulk (free) and hydration (bound) water during the extraction of Pt(IV) and Au(III) from acid sulfate-chloride media by Triton N-42 reverse micelles. The bulk water fraction in Triton N-42 micelles reduces from 44% to 23% with an increase in the sodium sulfate concentration up to 3.5 mol/l in the feed. A decrease in the total concentration of micellar water and bulk water fraction complies well with an increase in the Pt(IV) and Au(III) distribution coefficients and concentration during the extraction by Triton N-42 reverse micelles.     

Spectrophotometric determination of microamounts of scandium with o-chlorophenylfluorone and cetyltrimethylammonium bromide

The reaction of scandium(III) with o-chlorophenylfluorone (o-CIPF) in the presence of cetyltrimethylammonium bromide (CTMAB) has been studied. In an acetate buffer at pH 4.4, a red-purple complex is obtained, with maximum absorption at 569 nm and a molar absorptivity of 1.31 x 10(5)1.mole(-1).cm(-1). The composition of the complex is found to be 1:2:2 Sc-o-CIPF-CTMAB. Beer's law is obeyed over the range 0-12 mug/25 ml scandium. The proposed method has been used for determination of trace scandium in tungsten ores after its prior separation by solvent extraction.