Sodium Dodecyl Sulfate Micellar System Research Articles

Steady State and Time-Resolved Fluorescence Spectroscopy of Cinchonine Dication in Sodium Dodecylsulphate Micellar System.

This paper reports the influence of surface charge of the micelles on to the photophysical properties of a cinchonine dication (C2+) fluorophore in anionic, sodium dodecylsulphate (SDS), surfactant at premicellar, micellar and post-micellar concentrations in aqueous phase at room temperature. The magnitude of edge excitation red shift (EERS) in the fluorescence maximum of C2+ in bulk water solution is 1897cm- 1 whereas, in the case of SDS it is observed to be 1984cm- 1. The fluorescence decay curve of C2+ fits with multi exponential functions in the micellar system. The increase in lifetime of C2+ in SDS has been attributed to the increase in radiative rate due to the incorporation of C2+ at the micelle -water interface. The value of dynamic quenching constant determined is 16.9 M- 1. The location of the probe molecule in micellar systems has been justified by a variety of spectral parameters such as dielectric constant, ET (30), viscosity, EERS, average fluorescence decay time, radiative and non-radiative rate constants. All experimental results suggest that the C2+ molecule binds strongly with the SDS micelles and resides at micellar-water interface. The binding constant (Kb) calculated (3.85 × 105 M- 1) for C2+ in SDS revealed that the electrostatic forces mediate charge probe-micelle association.

Green synchronous spectrofluorimetric method for the simultaneous determination of agomelatine and venlafaxine in human plasma at part per billion levels

A novel sustainable, simple, sensitive, and green spectrofluorimetric method was developed for the concurrent estimation of venlafaxine and agomelatine in pharmaceuticals and biological fluids. The method relies on synchronous fluorescence spectroscopy, where venlafaxine and agomelatine were measured at 276 and 328 nm, respectively, using Δλ of 20 nm. The potential factors affecting the fluorescence intensity were optimized by the one-factor-at-a-time (OFAT) strategy, where synchronous fluorescence intensity was significantly enhanced using a 1% w/v sodium dodecyl sulfate micellar system. The method was fully validated and exhibited excellent linearity (r2 > 0.999 for both drugs) with very low limits of detection (LODs) in the range of 0.14–0.84 ng/mL. Consequently, the proposed approach was efficiently adopted to analyze the co-administered drugs in their pharmaceuticals and in spiked human plasma with excellent % recovery between 97.4 and 102.2%. Finally, the method's greenness was evaluated using different metric tools, including Green Analytical Procedure Index (GAPI) and Analytical GREEnness (AGREE), which proved its excellent greenness.

SANS characterization of time dependent, slow molecular exchange in an SDS micellar system.

We have investigated the molecular exchange of sodium dodecyl sulfate (SDS) micelles in aqueous solution by time-resolved small angle neutron scattering (TR-SANS) measurements as a function of the surfactant and salt concentration. Starting with deuterated (d-SDS) and protonated (h-SDS) SDS micelles, surfactant exchange across the micelles leads to a randomized distribution of d-SDS and h-SDS within each micelle. By employing the contrast matching technique, we have studied this randomization process which is a direct measure of the molecular exchange of this system. Our results show that the randomization of the pure h-SDS and d-SDS micelles occurs in two steps: first, an almost instantaneous drop in the scattering intensity is observed where ∼80% of the micelles are randomized (contrast matched). After this, micelle randomization progresses slowly spanning over ∼100 hours. Importantly, we show that the kinetics in the second step are dominated by the formation of domains rich in either h-SDS, d-SDS and randomized (50 : 50 h-SDS : d-SDS). The slow exchange step is modeled via a phenomenological approach by drawing analogy to the Langmuir adsorption theory. Finally, the effects of the surfactant and salt concentrations on the instantaneous, and the time dependent randomization of SDS micelles are discussed.

Microwave assisted accelerated fluoride adsorption by porous nanohydroxyapatite

Fluoride pollution of water is a matter of concern in many countries due to its association with chronic kidney failure. Therefore, it is important to develop fast and efficient methods for fluoride removal from drinking water using environmentally friendly materials. In this article, the synthesis, characterization and microwave assisted accelerated fluoride removal by porous nanohydroxyapatite (PHAP) are reported. The PHAP samples were synthesized using polyvinyl pyrrolidone and sodium dodecyl sulphate micellar system as the template. The prepared nanohydroxyapatite was characterized using TEM, SEM, FT-IR, TGA, XRD and BET. Investigation of the morphology of microcrystals using TEM showed the presence of spherical particles of 20–35 nm size and highly porous rod-shaped crystals with the aspect ratio of 2:13. The adsorption of F− ions using PHAP was carried out under the influence of microwave radiations using concentrations comparable to existing F− levels in natural water. The equilibrium is reached within 80 s and this is the fastest saturation time recorded for any existing material. The kinetic experiments showed that the fluoride adsorption is an activated second order process. The equilibrium fluoride adsorption capacity of PHAP was found to be 9.19 mg g−1 at pH 6.5 for 80 s and this was proven to be a potential material to remove F− ions rapidly from drinking water.

Photochemical Processes in Molecular Polymethine Dye Probes in the Presence of Bile Salts

Primary photochemical processes in polymethine dye probes 3,3′-di(γ-sulfopropyl)-4,5,4′,5′-dibenzo-9-ethylthiacarbocyanine betaine (DEC) and 3,3′,9-trimethylthiacarbocyanine iodide (Cyan 2) in micellar systems of bile-acid salts (BASs) sodium cholate, deoxycholate, and taurocholate and sodium dodecyl sulfate (SDS) as a reference are studied by flash photolysis. Signals due to photoisomerization of dye trans-isomers and dark reverse isomerization of the resulting cis-photoisomers are observed during pulse photolysis of air-saturated aqueous dye solutions in the presence of BAS and SDS micelles. The lifetimes of the photoisomers are 60–190 μs. Pulse photolysis of Cyan 2 and DEC solutions without oxygen and with BAS and SDS micelles induced photoisomerization and transition of the dyes into an excited triplet state followed by the reverse transition (intersystem crossing) into the initial singlet state. Triplet–triplet absorption spectra of these dyes isomers in polar (EtOH, i-PrOH) and nonpolar (dioxane) solvents were obtained for comparison using triplet–triplet energy transfer from anthracene. The conclusion was drawn that the photochemical behavior of the dyes in BAS and SDS micellar systems were similar.

Synthesis of fullerene (C60-monoadduct)-based water-compatible imprinted micelles for electrochemical determination of chlorambucil

A novel water-compatible C60-monoadduct based imprinted micelles was synthesized by the self-assembly of vinylic-C60-monoadduct with sodium dodecylsulfate micellar system, in the presence of chlorambucil as a model template (anticancer drug). After template retrieval with acetonitrile, these imprinted micelles were immobilized at the surface of ionic liquid decorated carbon ceramic electrode. Herein, C60-monoadduct (the head group of micelle) actually served as a nanomediator for electronic transmission across multiple interfaces. Such modification induced electrocatalytic characteristics by decreasing analyte oxidation overpotential and thereby augmented the electrode kinetics. Consequently, the differential pulse anodic stripping transduction was realized to be approximately four-fold as compared to the corresponding electrode modified without C60-monoadduct. This revealed the potential role of fullerene as nanomediator in the signal transduction. Herein, ionic liquids facilitated electron transport by two-fold without any interfacial barrier through carbon layers than that realized with modified ceramic electrodes made in the absence of ionic liquids. A perfect linearity in the current-concentration profile under optimal conditions was observed for the analyte concentration in the range 1.47–247.20ngmL-1, with the detection limits to the tune of 0.36ngmL-1 (S/N=3) in aqueous and real samples.

Effect of tartarate and citrate based food additives on the micellar properties of sodium dodecylsulfate for prospective use as food emulsifier

Citrate and tartarate based food preservatives can be used to enhance the emulsifying properties of sodium dodecylsulfate (SDS) based micellar system and thus making it appropriate for food applications. Exploration of interactions between the two species is the key constraint for execution of such ideas. In this work various micellar and thermodynamic parameters of SDS like critical micellar concentration (CMC), standard Gibbs free energy of micellization (ΔG0mic.) etc. have been calculated in different concentrations of disodium tartarate (DST) and trisodium citrate (TSC) in the temperature range (288.15–318.15)K from the conductivity and surface tension measurements. The parameters obtained from these studies reveal the competitive nature of both the additives with SDS for available positions at the air/water interface. TSC is found to be more effective additive in order to make SDS micellar system better for its potential applications as food emulsifier.

Probing effect of lipophilic butylated hydroxytoluene on anionic surfactant properties for potential food and pharmaceutical applications: Thermo-acoustic and spectroscopic study

Butylated hydroxytoluene (BHT), a lipophilic bio-active organic molecule and chemically, a phenol derivative added to many food materials to prevent fat spoilage and moreover, as additive to many pharmaceutical products. On the other hand, sodium dodecyl sulfate (SDS) has also been employed as major raw material by many industries. Taking into account the advantages of surfactant micelles as carriers, the impact of BHT on SDS micellar system has been studied in ethanol and in different percentage compositions of ethanol+water mixtures. Therefore, it would be interesting and of great value to evaluate the type of interactions occurring between BHT and SDS in order to design such system which could prove its validity in food or pharmaceutical formulations. In order to examine the micellar properties more clearly, we use simple and easily controlled approach to obtain critical micelle concentration (CMC) values using conductance κ along with experimentally determined density and speed of sound data to evaluate, apparent molar volume ϕv, apparent molar adiabatic compression ϕκ and isentropic compression κs of SDS in presence of BHT at variable temperatures (25, 30, and 35°C). Further, the thermo-acoustic parameters have also been evaluated using viscosity measurement. In addition, spectroscopic analysis (FTIR and proton NMR) confirmed the interaction between BHT and SDS and locus of BHT in micellar structure. Conclusively, this physicochemical study provides a hint to assess and develop surfactant immobilized BHT for better biological action.

Thermo-acoustic investigation in alcohol–water mixtures: Impact of lipophilic antioxidant on anionic surfactant properties for potential cosmeceutical application

In this present study, the self aggregation and solution properties of sodium dodecyl sulfate (SDS) in presence of lipophilic organic molecule i.e. butylatedhydroxyanisole (BHA) has been assessed by using simple and easily controlled approach to obtain CMC values and thermo-acoustic parameters via specific conductance (κ), viscosity (η), compressibility coefficient (β), apparent molar volume (ϕv) and apparent molar adiabatic compression (ϕk) at three different temperatures (25, 30, and 35°C). Taking into account the advantages of surfactant micelles as carriers, the basic impact and association of BHA on SDS micellar system has been studied in alcohol+water mixtures. It would therefore be interesting to evaluate the type of interaction between the moieties in order to design such surfactant aided immobilized system for better inhibitory action of BHA which could prove valuable to pharmaceutical or cosmeceutical industries.

Effect of Pharmaceutically Important Cosolvents on the Interaction of Promethazine and Trifluopromazine Hydrochloride with Sodium Dodecyl Sulfate Micelles

The present study is an attempt to gain a better understanding of the characteristics of binding of phenothiazine drugs; promethazine hydrochloride, and triflupromazine hydrochloride to sodium dodecyl sulfate micellar system in the presence of pharmaceutically important cosolvents, such as ethanol, ethyleneglycol, and propyleneglycol. The interactions of promethazine and triflupromazine hydrochloride with anionic surfactant sodium dodecyl sulfate in the absence and presence of various concentrations of cosolvents have been studied by absorption spectroscopy as a function of surfactant concentration ranging from the premicellar to postmicellar region at 298 K. The binding tendency of promethazine and triflupromazine hydrochloride to sodium dodecyl sulfate micelles decreased with the concentration of cosolvents increased. The addition of cosolvents increased the CMC of sodium dodecyl sulfate and at a certain concentration totally inhibited the micellization. The inhibitory effect of cosolvents on binding of promethazine and triflupromazine hydrochloride to micelles followed the order as; water > ethyleneglycol > propyleneglycol > ethanol. Polarity of the micellar microenvironment and probable location of promethazine and triflupromazine hydrochloride were also discussed in different micellar media.

Photocatalytic Hydrogen Evolution from Rhenium(I) Complexes to [FeFe] Hydrogenase Mimics in Aqueous SDS Micellar Systems: A Biomimetic Pathway

To offer an intriguing access to photocatalytic H(2) generation in an aqueous solution, the hydrophobic photosensitizer, Re(I)(4,4'-dimethylbpy)(CO)(3)Br (1) or Re(I)(1,10-phenanthroline)(CO)(3)Br (2), and [FeFe] H(2)ases mimics, [Fe(2)(CO)(6)(mu-adt)CH(2)C(6)H(5)] (3) or [Fe(2)(CO)(6)(mu-adt)C(6)H(5)] (4) [mu-adt = N(CH(2)S)(2)], have been successfully incorporated into an aqueous sodium dodecyl sulfate (SDS) micelle solution, in which ascorbic acid (H(2)A) was used as a sacrificial electron donor and proton source. Studies on the reaction efficiency for H(2) generation reveal that both the close contact and the driving force for electron transfer from the excited Re(I) complexes and [FeFe] H(2)ases mimics are crucial for efficient H(2) generation with visible light irradiation. Steady-state and time-resolved investigations demonstrate that the electron transfer takes place from the excited Re(I) complex 1 or 2 to [FeFe] H(2)ases mimic catalyst 3, leading to the formation of the long-lived Fe(I)Fe(0) charge-separated state that can react with a proton to generate Fe(I)Fe(II).H, an intermediate for H(2) production. As a result, a reaction vessel for the photocatalytic H(2) production in an aqueous solution is established.

Separation and determination of lignans from seeds of Schisandra species by micellar electrokinetic capillary chromatography using ionic liquid as modifier

In this paper, a micellar electrokinetic chromatographic (MEKC) method using ionic liquid as modifier for the quantification of the active components of lignans found in the medicinal herbs Schisandra species was developed for the first time. Preliminary investigations employing sodium dodecyl sulfate (SDS) as surfactant did not lead to the necessary resolution of the studied compounds, the addition of ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM-BF 4) to the SDS micellar system resulted in the complete separation of all the compounds. The effects on the separation by several parameters such as BMIM-BF 4 and SDS concentration, applied voltage, background electrolyte pH and concentration, were evaluated. Under the optimal conditions (5 mM borate-5 mM phosphate buffer in the presence of 20 mM SDS and 10 mM BMIM-BF 4, pH 9.2, applied voltage 25 kV and detection at 254 nm), the method successfully applied to the determination of lignans in extracts of Schisandra chinensis (Turcz.) Baill. and Schisandra henryi C.B. Clarke in less than 13 min. The separation mechanism was also discussed.

Analysis of lignans using micellar electrokinetic chromatography.

Micellar electrokinetic chromatography (MEKC) was used to separate twelve lignan compounds originating from Phyllanthus plants. To increase the reliability of peak identification, two micellar systems, the sodium dodecyl sulfate (SDS) and sodium deoxycholate (SDC) systems, were investigated. Because of the high lipophilicity of the lignan analytes, tetrahydrofuran was added to the SDS micellar system to increase its separating ability. In contrast to SDS system, no organic solvent was needed with SDC micelles. Both micellar systems gave a satisfactory separation within a reasonable analysis time. On considering accuracy for quantitation, the SDS method was validated and then used to determine the content of the lignans in two Phyllanthus plants. The selectivity (elution order of the lignans) was significantly different between the SDS and SDC micellar systems. Retention in SDC-MEKC seemed to be dominated by the hydrophobicity of the lignan solutes, while in SDS-MEKC, retention was greatly influenced by hydrogen bonding interactions.

Molecular Dynamics Simulations of Sodium Dodecyl Sulfate Micelle in Water: The Behavior of Water

Using a 5 ns explicit atom molecular dynamics simulation of a 60 monomer sodium dodecyl sulfate micellar system containing 7579 TIP3P water molecules, the behavior of water in different electrostatic environments was examined. Structural evaluation of the system revealed that penetration of water molecules into the micelle was restricted to the headgroup region, leaving a 12 A water-free hydrocarbon core. Water molecules near the headgroup exhibit a distortion of the water−water hydrogen bonding network due to headgroup oxygen−water hydrogen bond formation. The dynamic implications of this distortion are manifested in the decay of the dipole autocorrelation function, Φ(t) and translational diffusion coefficient. We observe that while the translational diffusion coefficient of water molecules in the first solvation shell of the micelle is reduced by less than a half of its value in bulk water, the slow component of the reorientational correlation function is slowed by one or two orders of magnitude.

Evaluation of hydrophobic properties of sodium dodecylsulfate/γ-alumina admicelles based on fluorescence spectra of N-phenyl-1-naphthylamine

Some molecular probes, whose fluorescence spectra were responsive to the polarity, were tested for monitoring the formation of admicelles. N-Phenyl-1-naphthylamine (PN) was the best choice for evaluating the hydrophobicity of sodium dodecylsulfate (SDS)/γ-alumina admicelles. The fluorescence intensity of PN in the aqueous suspension of the admicelles enhanced in the SDS concentration far below its critical micelle concentration. The intensity was greater than that in the normal SDS micellar system. Additionally, the wavelength at the maximum intensity of the fluorescence in the admicellar system was shorter than that in the micellar solution. These facts strongly suggest that the admicelles provide more hydrophobic environment than conventional micellar media. Comparison of the wavelength with those in several solvents indicated that the admicelles have hydrophobic properties corresponding to 1-octanol or ethyl acetate.

Determination of 5-aminosalicylic acid related impurities by micellar electrokinetic chromatography with an ion-pair reagent

A micellar electrokinetic chromatographic (MEKC) method was developed for the quantification of mesalazine or 5-aminosalicylic acid (5-ASA) and its major impurities 3-aminosalicylic acid, salicylic acid, sulfanilic acid and 4-aminophenol. The optimisation of the experimental conditions was carried out considering some important requirements: resolution, reproducibility, detection limits of 0.1% (m/m) or less, short total analysis time. Preliminary investigations employing sodium dodecyl sulfate (SDS) as surfactant did not lead to the necessary resolution of the studied compounds; the addition of tetrabutylammonium bromide (TBAB) to the SDS micellar system resulted in the complete separation of all the compounds. The effects on the separation by several parameters such as TBAB concentration, SDS concentration, background electrolyte pH and concentration, were evaluated. Using a fused-silica capillary (8.5 cm effective length) complete analysis was obtained in a very short time. Under the optimised final conditions [120 m M 3-(cyclohexylamino)-2-hydroxy-1-propanesulfonic acid buffer, pH 10.20, 65 m M SDS in the presence of 55 m M TBAB and 5% methanol] the method was validated for specificity, precision, linearity, limits of detection and quantitation, and robustness: the 5-ASA related impurities can be quantified at least at the 0.1% (m/m) level.

Effect of a variety of organic additives on retention and efficiency in micellar liquid chromatography

The effect of 21 organic additives (alkanols, alkane diols, dipolar aprotic solvents, alkanes) on the chromatographic behavior (retention, elution strength, efficiency) of probe solutes of widely differing hydrophobicity, such as benzene and 2-ethylanthraquinone, have been examined using a C18 stationary phase and sodium dodecyl sulfate (SDS) micellar mobile phases. The mobile-phase elution strength parallels the octanol-water partition coefficients of the additives or their ability to bind to the SDS micellar system, due to the increased solubility in the mobile phase and reduced affinity for the additive-modified surfactant-coated stationary phase. The comparison of the elution strength of micellar mobile phases with that of a reference acetonitrile-water system indicates that the elution strength is lower for micellar systems and depends on the nature of the eluted solute. The displacement of the solute-micelle and solute-stationary phase binding equilibria is quantified for several probe solutes eluted with micellar mobile phases in the presence of 1-propanol, 1-butanol, 1-pentanol, and acetonitrile. A correlation was also observed between the number of theoretical plates and the hydrophobicity of the alcohol additives: the efficiency initially increased steeply and reached a plateau. Compared to benzene, a more hydrophobic additive was needed to attain the maximum efficiency for the more hydrophobic 2-ethylanthraquinone analyte. Dipolar aprotic solvents appear to be somewhat more effective in enhancing the efficiency than alcohols. The results are rationalized in terms of the ability of the organic additives to alter the composition, structure, dynamics, and properties of the micelles and the surfactant-coated stationary phase.

Phase-separation induced by shear for a near-critical ionic micellar solution

We report shear effects in a near-critically ionic micellar system of sodium-dodecyl-sulfate (SDS)+butanol+NaCl+water, with varying NaCl concentration and shear rate. In the experiment, when the mixture is imposed to shearing at a homogeneous equilibrium region, highly elongated concentration-domains suggesting phase-separation appear in the direction of flow, and when the shear is turned off, those domains disappear in time and the homogeneous state is recovered. The temperature shift associated by shear, T p− T p,S, strongly depends on shear rate and NaCl concentration, where T p and T p,S are the phase-separation temperature in a quiescent state and that in a sheared state, respectively. These results indicate that the shear-induced phase-separation occurs in the SDS micellar system, in contrast to the shear-induced homogenization observed in nonionic micellar systems.

Electrically Driven Microseparation Methods for Pesticides and Metabolites: I. Micellar Electrokinetic Capillary Chromatography of Carbamate Insecticides with MEGA-Borate and SDS Surfactants

Abstract The migration behavior of some representative carbamate insecticides in micellar electrokinetic capillary chromatography (MECC) was investigated over a wide range of elution conditions, including the nature and concentration of the surfactant and the concentration of added urea in the running electrolyte. Decanoyl-N-methylglucamide (MEGA 10) surfactant was compared with the traditionally used sodium dodecyl sulfate (SDS) surfactant for separation of the carbamate insecticides under investigation. The MEGA 10 micellar system is based on the complexation of MEGA 10 with borate, yielding an in situ charged micelle (i.e., MEGA 10-borate micelle), whose surface charge density can be readily manipulated by varying the pH and the concentrations of borate and MEGA 10 in the running electrolyte. This flexibility, in turn, allowed the modulation of the migration time window and, consequently, the analysis time. Because of its relatively weaker hydrophobic character, the MEGA 10-borate micellar system permitted the resolution of 9 different carbamate insecticides in about 12 min. Conversely, with the SDS micellar system, whose hydrophobicity is higher, the separation of all 9 solutes necessitated the addition of 4.0M urea, a condition that brought about a doubling of the analysis time. In addition, the MEGA 10-borate micellar system produced twice as many plates per min as did the SDS micellar system. Because MEGA 10-borate yielded results superior to those of the SDS micellar system, on-column preconcentration of the carbamate insecticides was attempted in MEGA 10-borate by using the concept of field-amplified sample stacking (FASS). Thus far, only a few attempts have been made toward the application of FASS in MECC of neutral compounds such as carbamate insecticides.

Interaction of UV light-induced alpha-tocopherol radicals with lipids detected by an electron spin resonance prooxidation effect.

The reaction rate constants of the interaction between light-induced alpha-tocopherol radicals with unsaturated lipids in a heterogeneous system compared to a homogeneous system are of the same order of magnitude. The decay rates of compartmentalized alpha-tocopherol radicals were significantly reduced by using negatively charged sodium dodecyl sulfate (SDS) micelles. A partially resolved electron spin resonance (ESR) hyperfine structure was observed under the conditions of both high lipid concentrations in comparison to the alpha-tocopherol concentration and of a regular distribution of alpha-tocopherol molecules inside the heterogeneous lipid structures. Alpha-tocopherol radicals have a considerable prooxidation potential at higher concentrations. Ascorbic acid dissolved in the aqueous medium provokes very fast alpha-tocopherol radical recycling through the boundary layer between the aqueous medium and micelles. By contrast, very slow reactions such as those of alpha-tocopherol radicals with glutathione through this boundary layer are measurable. Despite using the heterogeneous SDS micellar system, the decay kinetics of the alpha-tocopherol radical ESR signal is simply compounded. In addition to the known stabilization effect of cholesterol in membrane systems, cholesterol itself acts as a target molecule attacked by free radicals, e.g. alpha-tocopherol radicals. Using stratum corneum extracts that contain unsaturated lipids and cholesterol the alpha-tocopherol radical can prooxidatively react with these compounds. Using focused UV light generates a high radical yield in a relatively short time compared to the lifetime of the alpha-tocopherol radicals. The decay processes after radical induction can be characterized as consecutive reactions. The compartmentalization of radicals induced in SDS micelles and the close proximity of target molecules are essential if very slow one-electron reductions are to be measured.