Sodium Dodecyl Sulfate Micellar Medium Research Articles

Kinetic study of Ru(III) – catalyzed oxidation of L-phenylalanine by hexacyanoferrate(III) in an anionic surfactant medium

Abstract The kinetic investigation of Ru(III) promoted oxidation of L-phenylalanine (L-PheAla) by [Fe(CN)6]3− has been performed in anionic sodium dodecyl sulfate (SDS) micellar medium by recording the decrease in absorbance at 420 nm corresponding to [Fe(CN)6]3− using an UV–visible spectrophotometer. Using the pseudo-first-order condition, the course of the reaction was studied as a function of [Fe(CN)6 3−], ionic strength, [OH−], [SDS], [Ru3+], [L-PheAla] and temperature by changing one variable at a time. The results exhibit that [OH−], [SDS], and [L-PheAla] are the crucial parameters that have an appreciable influence on the reaction rate. The reaction exhibits first-order kinetics in concentration ranges of Ru(III), [Fe(CN)6]3− and at low [L-PheAla] and [OH−] concentrations. The incremental trend observed in the reaction rate with electrolyte concentration shows a positive salt effect. The reaction rate is almost 10 times faster in SDS micellar medium than in aqueous medium. [Fe(CN)6]3− has no appreciable effect on the CMC of SDS, since the polar head of SDS and [Fe(CN)6]3− are both negatively charged. The K+ obtained from K3[Fe(CN)6] and KNO3 decreases the repulsion between the negatively charged heads of the surfactant molecules, which decreases the CMC of SDS. The activation parameters also support the outer-sphere electron transfer mechanism.

Heme-Aβ in SDS micellar environment: Active site environment and reactivity

Alzheimer's disease (AD), the most common cause of dementia, is a progressive neurodegenerative disorder that causes brain cell death. Oxidative stress derived from the accumulation of redox cofactors like heme in amyloid plaques originating from amyloid β (Aβ) peptides has been implicated in the pathogenesis of AD. In the past our group has studied the interactions and reactivities of heme with soluble oligomeric and aggregated forms of Aβ. In this manuscript we report the interaction of heme with Aβ that remains membrane bound using membrane mimetic SDS (sodium dodecyl sulfate) micellar medium. Employing different spectroscopic techniques viz. circular dichroism (CD), absorption (UV–Vis), electron paramagnetic resonance (EPR) and resonance Raman (rR) we find that Aβ binds heme using one of its three His (preferentially His13) in SDS micellar medium. We also find that Arg5 is an essential distal residue responsible for higher peroxidase activity of heme bound Aβ in this membrane mimetic environment than free heme. This peroxidase activity exerted by even membrane bound heme-Aβ can potentially be more detrimental as the active site remains close to membranes and can hence oxidise the lipid bilayer of the neuronal cell, which can induce cell apoptosis. Thus, heme-Aβ in solution as well as in membrane-bound form are detrimental.

Micelle core as a nest for residence of molecular oxygen – An electrochemical study

• Mapping out of solubility and transport scenario of O 2 in an organized micellar media through the study of electrochemical oxygen reduction reaction (ORR). • Simultaneous determination of saturation concentration ( C o 2 ) and diffusion coefficient ( D o 2 ) of O 2 in SDS micellar medium by studying ORR. • Identification of the ascending trend of C o 2 with increasing concentration of SDS and verification of the acceptability of excess C o 2 in SDS with computer simulation. • Recognizing the micro-domains of micelles studied with dynamic light scattering as the nest for residence of O 2 and as a high-density, slow-releasing warehouse of O 2 . The solubility and diffusibility of molecular O 2 are critically important in many chemical, biological, electrochemical, energy generation and storage systems. In this work, by the study of electrochemical O 2 reduction reaction (ORR), the solubility and transport scenario of O 2 in organized micellar media as monitored with dynamic light scattering measurement were mapped out. The ORR was investigated in aqueous H 2 SO 4 solution and micellar medium of sodium dodecyl sulfate (SDS) at glassy carbon and platinum electrodes using cyclic voltammetric and chronoamperometric techniques. The ORR studied in both media was found to be an irreversible, diffusion-controlled process. The diffusion coefficient ( D o 2 ) and the saturation concentration of O 2 ( C o 2 ) were determined by studying the ORR with chronoamperometry and steady-state voltammetry. The D o 2 was found to be lower in micellar system compared to the aqueous solution, whereas the C o 2 determined in 0.200 M micellar medium of SDS was about 15-fold higher than that of H 2 SO 4 solution. The characteristics of the ORR studied and the values of D o 2 and C o 2 determined in micellar media were verified by simulation software for cyclic voltammetry. Higher solubility of O 2 is revealed in the hydrophobic micro-domains of micelles that behave as a nest for the residence of O 2 and may serve as a high-density, slow-releasing warehouse of molecular O 2 . This study opens a noble route for designing molecular shuttles assisting O 2 to maintain its flow in a system containing O 2 permeable membranes.

UV-VIS spectrophotometric determination of magnesium after complexing with 8-hydroxy quinoline in sodium dodecyl sulphate micellar medium

In this study, an alternatifive UV-VIS spectrophotometric method for determination of magnesium was proposed. The method is based on complexation with 8-hydoxyquinoline (oxin) in sodium dodecyl sulphate (SDS) micelle medium, the absorbance of the product was recorded at 390 nm. pH of the solution, the concentration of ligand and surfactant were critical parameters, which affect the absorbance measurements, and optimised. The molar absorptivitiy coefficient is 5×102 Lmol-1cm-1, the Sandell’s sensitivity is 0,052 µgcm-2, detection limit is 0,3 mgL-1, quantification limit is 1,1 mgL-1 and linear working range is 2-8 mgL-1 at pH 12 and 390 nm. The proposed method was applied for determination of magnesium to some drug and mineral water samples, nearly good accuracy and reproducible volues were obtained percent as recovery and relative standart deviation.

A Versatile Water-Stable Fluorine Containing Organometallic Lewis Acid Used in Green Synthesis of 1,3-Oxazine Scaffolds at Room Temperature

A simple, straightforward, and highly efficient one-pot multicomponent synthesis of pharmaceutically interesting [1,3]-oxazine derivatives has been developed using iron(III) trifluroacetate ([Fe(CF3CO2)3]) as Lewis acid in an aqueous sodium dodecyl sulfate (SDS) micellar medium. The salient features of the present protocol are mild reaction conditions, use of aqueous SDS micellar medium, good yields, eco-friendly standards, easy isolation of products, no column chromatographic separation and reusability of catalytic system. The synthesized some chromeno[1,3]oxazine derivatives were tested for their antioxidant activity using free radicals DPPH method. The screened compounds showed moderate to good activity on comparison with ascorbic acid.

Efficient synthesis of Mannich bases by sonication in sodium dodecyl sulfate micellar media

Water is a desirable solvent for synthesis because water is cheap, safe and non-toxic. However, the use of water as solvent is limited to water-soluble compounds, thus excluding most organic, lipophilic substances. A solution to this issue is to increase the solubility of organic compounds by using a surfactant to form micelles and, in turn, increase contacts with the reagent. Here, we tested ultrasound irradiation and sodium dodecyl sulfate micellar media on Mannich reaction of aldehydes, aromatic amines and acetophenone derivatives or cyclohexanone. The sonication of biphasic systems was performed at 37 kHz, 300 Watt, under neutral conditions. Results show that the reaction is carried out readily under milder conditions. The precipitated solid Mannich product was recovered by a simple filtration without using any organic solvent. This method provides advantages such as short reaction time, mild reaction conditions and simple work-up.

Electrochemical reduction and quantification of menadione in sodium dodecyl sulfate micellar media

Menadione cyclic voltammograms show a pair of redox steps on glassy carbon electrode in 0.1 M H3PO4 with potential separation of 343 mV. Cationic, nonionic, and anionic surfactants micellar media significantly decrease the menadione peak potential separation. Statistically significant increase of menadione reduction current (3- and 4.4-fold) has been observed in Triton X 100 and sodium dodecyl sulfate (SDS) micellar media, respectively. Electrochemical reduction of menadione in 9 mM SDS micellar media is reversible diffusion-controlled one-electron process corresponding to formation of relatively stable semiquinone anion radical. The linear dynamic ranges of menadione determination are 7–560 and 600–2,550 μM with the limits of detection and quantification of 1.66 and 5.53 μM, respectively. The current concentration sensitivity is (8.6 ± 0.2) × 103 μA μM−1. The voltammetric method for the determination of menadione in pharmaceutical “Aekol” based on preliminary extraction with ethanol has been developed.

Synthesis by in situ chemical oxidative polymerization and characterization of polyaniline/iron oxide nanoparticle composite

AbstractPolyaniline (PANI) is a well‐studied material and is the pre‐eminent electrically conducting organic polymer with the potential for a variety of applications such as in batteries, microelectronics displays, antistatic coatings, electromagnetic shielding materials, sensors and actuators. Its good environmental as well as thermal stability and electrical conductivity tunable by appropriate doping make PANI an ideal active material for several applications. In this paper, we report the synthesis of water‐dispersible colloidal PANI/iron oxide composite nanoparticles using an in situ chemical oxidation polymerization method in a micellar medium of sodium dodecylsulfate, where the cores (iron oxide) are embedded in a PANI matrix layer. Transmission electron micrographs showed evidence of the formation of an iron oxide core/PANI shell composite with a thin layer of PANI over the iron oxide cores. The results of thermogravimetric, Fourier transform infrared and UV‐visible analysis indicated that the iron oxide nanoparticles could improve the composite thermal stability possibly due to the interaction between iron oxide particles and PANI backbone. We believe that the synthetic route described can also be adapted for the assembly of hierarchical structures of other metal oxides or hydroxides onto various cores. Copyright © 2010 Society of Chemical Industry

A highly efficient michael addition of indoles to α,β-unsaturated electron-deficient compounds in acidic SDS micellar media

The Michael addition of indoles to α,β-unsaturated electron deficient compounds was catalyzed efficiently at room temperature in acidic micellar solution of sodium dodecyl sulfate (SDS). The substitution on the indole nucleus occurred exclusively at the 3-position in good to excellent yields, and no N-alkylation products were observed.

Photoreaction of Thioxanthone with Indolic and Phenolic Derivatives of Biological Relevance: Magnetic Field Effect Study

The photoinduced reaction of thioxanthone (TX) with various indolic and phenolic derivatives and amino acids like tryptophan and tyrosine has been monitored in sodium dodecyl sulfate micellar medium. Laser flash photolysis and magnetic field effect (MFE) experiments have been used to study the dynamics of the radical pairs. The quenching rate constant with different quenchers in SDS micellar solution has been measured. For indoles the electron-transfer reaction has been found to be followed by proton transfer from the donor molecule, which gives rise to the TX ketyl radical. On the other hand, the electron-transfer reaction in the case of phenols is preceded with formation of a hydrogen-bonded exciplex. The extent of the MFE and magnitude of the magnetic field corresponding to one-half of the saturation value of MFE ( B 1/2) support the fact that hyperfine mechanism plays the primary role. Quenching of MFE in the presence of gadolinium ions confirms that the radical pair is located near the micellar interface. MFE study has been further extended to protein-like bovine serum albumin in micellar solution. The results indicate loss in mobililty of radical pairs in the protein surfactant complex.

Selective and Stability-Indicating Methods for the Simultaneous Determination of Mexiletine Hydrochloride and/or Its Related Substance: 2,6-Dimethylphenol

Four simple, rapid, sensitive, and selective analytical procedures were developed for determination of mexiletine hydrochloride (MX) and/or its related substance: 2,6-dimethylphenol (DMP). The latter is a synthetic impurity for which a maximum pharmacopeial limit is defined. The first method depends on derivative-ratio spectrophotometry, for which the first-derivative signals of the ratio spectra at 259 nm (Deltalambda = 3 nm) are selected for the determination of MX. The second method is based on the spectrofluorometric measurement of MX in alkaline solution in the presence of 15 mM sodium dodecyl sulfate micellar medium at 292 nm (lambdaEx 260 nm). The third method is based on liquid chromatographic (LC) separation of MX and DMP on an RP-C8 column with a mobile phase consisting of 50 mM Na2HPO4-acetonitrile (60 + 40, adjusted to pH 2.4), and quantification of the analytes is achieved with UV detection at 212 nm based on peak area. The fourth method uses the coupling reaction of DMP with 2,6-dibromo-quinone-4-chlorimide (DBQC) in borate buffer to form an intensely colored product that was spectrophotometrically measured using first-derivative amplitudes at 670 nm (Deltalambda = 6 nm) for the determination of DMP. Different variables affecting each method were carefully investigated and optimized. The reliability and analytical performance of the proposed methods, including linearity, range, precision, accuracy, and detection and quantitation limits, were statistically validated. The first 3 methods were successfully applied for the stability-indicating determination of MX in laboratory-prepared mixtures with DMP, as well as for the determination of MX in capsules. Also, the LC and the DBQC spectrophotometric methods permitted the selective determination of DMP in the presence of a large excess of the parent drug at or near the pharmacopeial limit (0.1-1%).

Simple synchronous fluorimetric method for determination of benzo[a]pyrene in airborne particulates without a pre-separation procedure

A sensitive analytical method, constant-energy synchronous fluorimetry, has been used to determine benzo[a]pyrene (BaP) selectively in airborne particulates (AP). A constant-energy difference of 1 400 cm−1 was selected for obtaining single spectral peak. The method could easily identify BaP in an 18-component polycyclic aromatic hydrocarbons(PAHs) mixtures. Calibration plots in methanol solution and in sodium dodecylsulfate (SDS) micellar media show a good linearity (R>0.999) in the BaP concentration range generally found in the environment. The method gives a detection limit of 0.40 nmol/L in SDS micellar medium and 1.34 nmol/L in methanol solution.

A new strategy for the chemiluminescent screening analysis of total N-methylcarbamate content in water

A new procedure for the screening of total N-methylcarbamate (NMCs) content in water at different concentration levels is here presented. It is based on a previous off-line alkaline hydrolysis of the NMCs, for the production of methylamine (MA), and its subsequent derivatisation with o-phthalaldehyde (OPA). After that, the obtained derivative is involved in the peroxyoxalate chemiluminescent (PO-CL) reaction using imidazole as a catalyst being the CL emission proportional to the total NMC content. The chemiluminescent reaction is carried out in a flow injection analysis (FIA) manifold, employing sodium dodecyl sulphate micellar medium as carrier, which avoids the rapid degradation of POs in water solution. The applicability of the screening method is shown for the monitoring of NMCs in natural waters. Analytical features, as specification limit signal, screening uncertainty, sensitivity and specificity, are calculated.

Determination of a N-methylcarbamate pesticide in environmental samples based on the application of photodecomposition and peroxyoxalate chemiluminescent detection

A new sensitive analytical procedure for the determination of a N-methylcarbamate pesticide (carbaryl) is presented, based on the participation of a fluorescent derivative of the pesticide in the peroxyoxalate chemiluminescent (PO–CL) system using imidazole as a catalyst. The chemiluminescent emission is detected in a flow injection (FI) manifold, employing sodium dodecyl sulfate micellar medium as carrier, which avoids the rapid degradation of a PO in water. The formation of the fluorescent derivative implies the previous decomposition of carbaryl to methylamine (MA) by UV irradiation and subsequent derivatisation with o-phthalaldehyde (OPA), carried out off-line. Photodecomposition allows a rapid degradation of carbaryl in MA, which implies some advantages in relation to the traditional hydrolysis in alkaline medium, such shorter analysis time and easier application. The optimisation of the operational and chemical variables affecting the CL response was carried out by using experimental design strategies. The method has been successfully applied to different natural waters and vegetal sample, obtaining satisfactory recoveries in both cases, with detection limits in compliance with the maximum limit of residues (MLR) permitted.

Second and first-derivative spectrophotometry for efficient simultaneous and individual determination of palladium and cobalt using 1-(2-pyridylazo)-2-naphthol in sodium dodecylsulfate micellar media.

1-(2-Pyridylazo)-2-naphthol (PAN) has been used for the simultaneous and individual determination of palladium and cobalt at trace levels. PAN complexes of palladium and cobalt at neutral pH form green-color neutral complexes, which are soluble in aqueous SDS micellar media. Under optimum conditions, calibration graphs for individual determinations by zero and first-derivative spectrophotometry, and also for simultaneous determinations by second-derivative spectrophotometry were obtained. A zero-crossing method using second-derivative spectrophotometry at 628 or 578 and 614 nm, respectively, for cobalt and palladium was used for simultaneous determinations. The method is able to determine the cobalt-to-palladium ratio, 5:1 to 1:10 (Wt/Wt), accurately. The accuracy and reproducibility of the determination method for various known amounts of cobalt and palladium in their binary mixtures were tested. The effects of diverse ions on the determination of cobalt and palladium to investigate the selectivity of the method were also studied. The recommended procedures were applied to a synthetic binary alloy, cobalt in vitamin B12 and B-complex ampoules, a Co2O3-Co3O4 laboratorial chemical mixture, some synthetic cobalt-alloy samples, a Pd-charcoal catalyst, and some synthetic palladium alloys.

A facile spectrophotometric method for cobalt determination using alpha-benzilmonoxime in sodium dodecylsulfate micellar solutions.

Alpha-benzilmonoxime in sodium dodecylsulfate micellar media has been used for the spectrophotometric determination of cobalt at pH 9.0. The linear range of calibration is 0.05-1.50 microg cm(-3) of cobalt at 380 nm with molar absorptivity of 3.72 x 10(4) dm3 mol(-1) cm(-1), which is about 1.5-times greater than that of the alpha-benzilmonoxime extraction based method. The relative standard deviations, recoveries, detection limit and effects of diverse ions on the determination of cobalt were studied. These analytical results were satisfactory. The method was successfully applied to the determination of cobalt in the various samples.

Spectral, kinetic, and redox properties of basic fuchsin in homogeneous aqueous and sodium dodecyl sulfate micellar media

AbstractEffect of anionic surfactant on the optical absorption spectra and redox reaction of basic fuchsin, a cationic dye, has been studied. Increase in the absorbance of the dye band at 546 nm with sodium dodecyl sulfate (SDS) is assigned to the incorporation of the dye in the surfactant micelles with critical micellar concentration (CMC) of 7.3 × 10−3 mol dm−3. At low surfactant concentration (<5 × 10−3 mol dm−3) decrease in the absorbance of the dye band at 546 nm is attributed to the formation of a dye–surfactant complex (1:1). The environment, in terms of dielectric constant, experienced by basic fuchsin inside the surfactant micelles has been estimated. The association constant (KA) for the formation of dye–SDS complex and the binding constant (KB) for the micellization of dye are determined. Stopped‐flow studies, in the premicellar region, indicated simultaneous depletion of dye absorption and formation of new band at 490 nm with a distinct isosbestic point at 520 nm and the rate constant for this region increased with increasing SDS concentration. The reaction of hydrated electron with the dye and the decay of the semireduced dye are observed to be slowed down in the presence of SDS. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 629–636, 2003

Fluorescence lifetime and quantum yield of TMPyPH 2 associated with micelles and DNA

In this work, we have determined the fluorescence lifetime and quantum yield of meso-tetrakis (4- N-methylpyridyl)porphine (TMPyPH 2) in cationic, anionic and non-ionic micellar media and in buffer phosphate solutions of DNA in order to evaluate how their electrostatic domain affects the photophysical properties of TMPyPH 2. The results obtained indicated that each specific electrostatic domain in micellar medium and in DNA solution affect the photophysical properties of the porphyrin. In anionic micellar medium of sodium dodecylsulfate (SDS) the electrostatic interacting of TMPyPH 2 with the medium leads to a Φ f value higher and τ f longer than those obtained in cationic medium of cetyltrimethylammonium bromide (CTAB) micelles. The interaction of TMPyPH 2 with a biological staff as DNA results initially in two different populations of a complex DNA–TMPyPH 2. The τ 1 for the first complex species changes in the function of DNA concentration in the ranges from 5.25 (‘free’ porphyrin species) to 11.3 ns (‘completely bound’ species) and the τ 2 for the second complex remains constant around 3 ns. It also was observed that DNA binding leads to a reduction in the fluorescence quantum yield of TMPyPH 2 to all DNA concentrations. This is an indication that the photodynamic properties of this porphyrin interacting with DNA are susceptible to the environmental properties affecting directly their photodynamic action.

Kinetic and redox characteristics of semireduced species derived from phenosafranine in homogeneous aqueous and sodium dodecyl sulfate micellar media

AbstractOne‐electron reduction of phenosafranine (PS+ 3,7‐diamino‐5‐phenylphenazinium chloride), a phenazinium dye, has been studied in homogeneous aqueous and sodium dodecyl sulfate (SDS) micellar media, using the pulse radiolysis technique. The various reducing radicals employed for the study in homogeneous aqueous medium were eaq−, H˙, CO2,˙−, and isopropyl ketyl radicals (CH3)2 ˙COH. Semireduced species generated by these reactions have been characterized by their absorption spectra, decay kinetics, and pKa. The one‐electron reduction potential of PS+ was determined at pH 7 in homogeneous aqueous solution employing nitrobenzene (NB/NB˙−) as the standard couple. One‐electron reduction in SDS micellar medium and a detailed spectrophotometric investigation of the parent dye in this surfactant system was carried out in order to understand the dye–surfactant interactions in the micellar and premicellar media.© 2001 John Wiley & Sons, Inc. Int J Chem Kinet 34: 56–66, 2002

Spectrophotometric determination of submicrogram amount of zinc with 5-(2'-carbomethoxyphenyl)azo-8-quinolinol in the anionic micellar medium of sodium dodecylsulfate

Spectrophotometric determination of submicrogram amount of zinc with 5-(2'-carbomethoxyphenyl)azo-8-quinolinol in the anionic micellar medium of sodium dodecylsulfate