Dodecyl Sulfate Solution Research Articles

The stability and solubility of cadmium(II)-8-oxyquinoline complexes in water and micellar solutions of sodium dodecyl sulfate

The formation of cadmium 8-oxyquinoline (HOx) complexes in water and a 0.01 M aqueous solution of sodium dodecyl sulfate (293 K, 0.01) was studied by pH-metric titration. Mathematical simulation of the most probable equilibria gave complex formation constants logβ1 = 6.17 ± 0.32 (CdOx+) and logβ2 = 14.60 ± 0.14 (CdOx2) in aqueous solution and apparent stability constants logβ1 = 8.64 (CdOx+) and logβ2 = 17.59 (CdOx2) in a solution of dodecyl sulfate. The solubility of cadmium dioxyquinolate in water at pH from 3 to 6 and a micellar sodium dodecyl sulfate medium was determined by the method of saturated solutions. The solubility product pLp = 21.3 ± 0.9 (H2O, 293 K) was calculated by modeling the solution of CdOx2 with taking into account all acid-base interactions and complex formation reactions.

Impedance spectroscopy analysis in a complex system: Sodium dodecyl sulfate solutions

Impedance measurements in the range 10–107 Hz were carried out in water solutions of sodium dodecyl sulfate for concentrations below and above critical micellar concentration (cmc). The results were analysed using a series combination of two Voigt units, describing bulk and interface process and, additionally, an unexpected inductive one, problably due to inertial effects of an adsorbed layer of SDS molecules at the electrode. The interface processes, including the inductive one, show transition at a concentration somewhat below cmc.

Polymerization of vinyl monomers in separated Winsor II (w/o) and Winsor I (o/w) microemulsion phases. Part 1: preparation and characterization of polymerizable vinyl-monomer-containing microemulsions

Classical toluene-based (w/o, water in oil) single-phase Winsor IV inverse microemulsions containing toluene/(sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/water/acrylamide (AAm)/sodium dodecyl sulphate (SDS) and containing, besides AAm, also an oil-soluble vinyl monomer (butyl acrylate (BA), styrene (S), or ethyl acrylate (EA)) were titrated by aqueous titrating systems (TS) composed from water (TA), aqueous solutions of acrylamide (TB), aqueous solutions of sodium dodecyl sulfate (TC), and/or aqueous solution of acrylamide and sodium dodecyl sulphate (TD). The amount of TS absorbed by the inverse microemulsion during titration (i.e., before transformation of Winsor IV inverse microemulsion to the two-phase Winsor II (w/o) (microemulsion phase + aqueous phase) and/or before phase inversion to the Winsor I (o/w) (microemulsion phase + oil phase) microemulsions, depended only slightly on the nature of the oil-soluble vinyl monomer. It was found, however, that the ratios of intra-phase and inter-phase compositional parameters such as toluene/AOT and AOT/SDS of the single-phase Winsor IV (w/o) inverse microemulsions considerably affected the value of the volume fractions of the aqueous phase, Φaw2, necessary for the formation of a two-phase Winsor II (w/o) and/or Winsor I (o/w) microemulsion systems. The composition of the titrating systems TS influenced the Φaw2 values at which the phase separation, and/or phase inversion of the single-phase Winsor IV (w/o) inverse microemulsion, were observed. Thus, the following sequence TAS1 < TA ≪ TC < TB < TD of titrating systems (ordered according to the obtained Φaw2 values) was found.

Temperature induced restoration of fluorescence from oxidised single-walled carbon nanotubes in aqueous sodium dodecylsulfate solution

Fluorescence intensity from single walled carbon nanotubes in aqueous sodium dodecylsulfate solution is shown to be strongly temperature dependent in the range 5-60 degrees C. Emission peaks corresponding to particular nanotube species which have been quenched due to oxidation by aerated water show sharp transitions at distinct temperatures as the sample is heated. The temperature at which the transition occurs is found to be species dependent and has been interpreted as being proportional to the valence band edge potential of the nanotube. The results are explained quantitatively using the Nernst equation to measure the increase in reduction potential of the solution as the temperature is raised. The removal of dissolved O(2) and CO(2) is thought to be a significant driving force in the reversal of the redox reaction which causes oxidation of the nanotubes.

Enzymatic oxidation of dipyridamole in homogeneous and micellar solutions in the horseradish peroxidase–hydrogen peroxide system

Enzymatic oxidation of dipyridamole (DIP) by horseradish peroxidase–hydrogen peroxide system (HRP–H 2O 2) in aqueous and micellar solutions was carried out. The reaction was monitored by optical absorption and fluorescence techniques. In aqueous solution at pH 7.0 and pH 9.0, the disappearance of the characteristic bands of DIP centered at 400 nm and 280 nm was observed. A new strong band at 260 nm is observed for the oxidation product (s) with shoulders at 322 nm and 390 nm. A non-fluorescent product is formed upon oxidation. In cationic cethyl trimethyl-1-ammonium chloride (CTAC) and zwitterionic 3-( N-hexadecyl- N, N-dimethylammonium) propane sulfonate (HPS) micellar solutions the same results are observed: three, well-defined, isosbestic points in the optical spectra suggest the transformation between two species. In anionic micellar sodium dodecylsulfate solution (SDS), the appearance of a new band centered around 506 nm was observed, associated to a solution color change from the usual yellow to deep blue/violet, characteristic of a radical species associated to the one-electron oxidation of DIP to its cation radical ( DIP· +), observed previously in electrochemical oxidation. Experiments of radical decay kinetics monitoring the absorbance change at 506 nm were performed and analyzed in the frame of a kinetic model taking into account the species both in homogeneous and micellar media. The reaction medium is composed of bulk solution, SDS micelle/solution interface and enzyme catalytic site (s). The variation of DIP· + concentration was analyzed assuming: (1) synthesis of DIP· + by HRP through one-electron oxidation; (2) decomposition of DIP· + by further one-electron oxidation; (3) direct two-electron oxidation of DIP by HRP; (4) bimolecular DIP· + disproportionation. The main results of the analysis are as follows: (1) kinetic data can be divided in two phases, an HRP active phase and another phase which proceeds in the absence of enzyme activity due to consumption of all H 2O 2; (2) the reactions of DIP· + formation, DIP· + decomposition and DIP two-electron oxidation are HRP concentration dependent; (3) since DIP· + formation constant seems to be overestimated, it is proposed that two-electron oxidation is another source of DIP· +, through the comproportionation reaction. Evidences for this reaction were also observed previously in electrochemical experiments; and (4) the kinetic analysis provides evidences that the bimolecular reaction of DIP· + takes place mainly in the absence of active HRP and in this phase the combination of, at least, two second-order kinetic processes is needed to model the experimental data. Our data suggest that HRP oxidizes DIP in general by a two-electron process or that the cation radical is very unstable so that the one-electron process is only detected in the presence of anionic surfactant, which stabilizes significantly the DIP· + intermediate.

Synthesis and spectroscopic characterization of trans-[Co(en)2(NO2)2]X (X = dodecyl sulfate, picrate, diclofenac or saccharinate) and the single-crystal X-ray structure of the saccharinate salt, trans-[Co(en)2(NO2)2](C7H4NSO3)·H2O

trans-[Co(en)2(NO2)2]X complexes, where X = C12H25SO4 (1), C6H2N3O7 (2), C14H10Cl2NO2 (3) and C7H4NSO3 (4), have been synthesized by slowly mixing aqueous solutions of trans-dinitrobis(ethylenediamine)cobalt(III) nitrate and sodium dodecyl sulfate, picrate, diclofenac and saccharinate, respectively, at a 1 : 1 mol ratio. Good crystals of trans-dinitrobis (ethylenediamine)cobalt(III) saccharinate monohydrate, [Co(en)2(NO2)2](C7H4NSO3)·H2O, were obtained. The salt is orthorhombic, space group P21212, with a = 21.553(2), b = 8.503(1), c = 10.238(1) Å, Z = 4, V = 1876.3(3) Å3, R 1 = 0.0286 and wR 2 = 0.0727. A structure determination revealed an ionic structure consisting of discrete [Co(en)2(NO2)2]+ cations and [C7H4SO3N]– anions.

Interaction of a Cationic Polymeric Flocculant with Anionic Stabilizers in Latex

Turbidimetric titration of aqueous solutions of sodium dodecyl sulfate and Leukanol and coagulation titration of polystyrene and polybutadiene latexes containing various amounts of these surfactants are performed.

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)63-/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.

Aqueous Micellar Solvent Extraction of Phenol from Wastewater

In aqueous micellar solvent extraction (AMSE), an organic solute is extracted from an aqueous solution across an ultrafiltration membrane into a solvent consisting of an aqueous micellar surfactant solution. The solute crossing the membrane is solubilized in the surfactant micelles, which are retained by the membrane. Phenol was extracted from water into an aqueous solution of sodium dodecyl sulfate (SDS) in hollow fiber membrane contactors of 5 K and 10 K molecular weight cutoff. The objectives were to determine the effect of bulk flow across the membrane on the transfer of phenol, and to measure the extent of back contamination of the wastewater by surfactant. Cocurrent flow of solvent and wastewater with equal transmembrane pressure differences at each end of the module were used to impose uniform bulk flows. Extractions with a range of bulk flowrates across the membrane in either direction yielded smaller overall diffusive mass transfer coefficients than the value with no bulk flow, which was approximately 2 µm/s. Back contamination of the wastewater by the surfactant was reduced by lowering the CMC of the solvent.

Metal Ion Buffer Systems for Ionometry in Water-Ethanol Mixtures and Micellar Medium of Sodium Dodecyl Sulfate

The concentration dissociation constants of nitrilotriacetic acid and the concentration stability constants of Cd(II) complexes with the nitrilotriacetic acid anion in water-ethanol mixtures and of Cu(II) and Cd(II) complexes with o-phenanthroline and 2,2′-bipyridine in micellar solutions of sodium dodecyl sulfate were determined potentiometrically. Based on the concentration constants determined, Cd2+ and Cu2+ buffer solutions were developed for calibration of a Cd2+-selective electrode in water-ethanol mixtures and Cd2+ and Cu2+-selective electrodes in micellar solutions of sodium dodecyl sulfate within the ranges pCu 9.7–13.5 and pCd 7.5–11.8.

Analysis of heat-processed corn foods for fumonisins and bound fumonisins

Thirty retail samples of heat-processed corn foods, i.e. corn flakes, corn-based breakfast cereals, tortilla chips and corn chips, were analysed for fumonisins — fumonisin B1 (FB1), fumonisin B2 (FB2) and hydrolysed FB1 (HFB1) — as well as for protein- and total-bound FB1. Bound (hidden) fumonisins cannot be detected by conventional analysis. Improved methods for the determination of bound FB1 were developed. The protein-bound FB1 was extracted with 1% sodium dodecylsulfate (SDS) solution. The SDS, which interfered with high-performance liquid chromatography (HPLC) analysis, was then separated from protein-bound FB1 by complexing with methylene blue followed by solvent extraction and hydrolysis with 2 N KOH. To measure total-bound FB1, the sample itself was hydrolysed with KOH. In both cases, clean-up was accomplished on an OASIS polymeric solid-phase extraction column and the bound fumonisins were determined by HPLC measurement of HFB1. Fourteen of 15 samples of corn flakes and other corn-based breakfast cereals analysed contained detectable levels of FB1 with a mean in positive samples of 67 ng g−1 (13–237 ng g−1). Two samples also had detectable levels of FB2 (21–23 ng g−1). Bound FB1 was found in all samples; the mean protein-bound FB1 measured was 58 ng g−1 (22–176 ng g−1) and the mean total-bound FB1 measured was 106 ng g−1 (28–418 ng g−1), reported as FB1 equivalents after correction for recoveries of HFB1. There was an average of about 1.3 times more FB1 in the bound form compared with extractable FB1, and this was about twice as much as protein-bound FB1. Seven of the 15 samples of alkali-processed corn-based foods, such as tortilla chips and corn chips, contained FB1 and three contained HFB1 with means in measurable positive samples of 78 (48–134) and 29 (13–47) ng g−1, respectively. Five of these alkali-processed corn foods contained bound FB1; the mean measurable protein-bound FB1 was 42 ng g−1 (39–46 ng g−1) and the mean measurable total-bound FB1 was 100 ng g−1(54–209 ng g−1). HFB1 derived from bound FB1 in selected samples was confirmed by HPLC with mass spectrometry (MS).

The wettability of polytetrafluoroethylene by aqueous solutions of sodium dodecyl sulfate and propanol mixtures

Advancing contact-angle ( θ ) measurements were carried out with aqueous solutions of propanol and four series of aqueous solutions of dodecyl sulfate (SDDS) and propanol mixtures at constant dodecyl sulfate concentrations equal to 1 × 10 −5 , 6 × 10 −4 , 1 × 10 −3 , and 1 × 10 −2 M , respectively. The obtained results indicate that in the range of propanol concentrations studied there were considerable contact-angle changes, with exception of the solution series at a constant concentration value of SDDS higher than its critical micelle concentration. From the results of contact-angle measurements and application of the Gibbs and Young equations the ratio of the excess concentration of surfactant and propanol at the solid–aqueous solution interface to the excess of their concentration at the aqueous solution–air interface was calculated. From the calculations it appears that there is a straight linear dependence between the adhesion tension and surface tension of aqueous solutions of SDDS and propanol mixtures, and the slope of the line is equal to −1, which suggests that the surface excess of the SDDS and propanol mixture at the polytetrafluoroethylene–solution interface is the same as the at the solution–air interface. The extrapolation of the straight line to the point corresponding to the surface tension of the aqueous solution, which completely spreads over the polytetrafluoroethylene surface, gives a critical surface tension of wetting equal to 23.7 mN/m. On the basis of the critical surface tension and the Young and modified Szyszkowski equations it was found that in a polytetrafluoroethylene–aqueous solution of the SDDS and propanol mixture, the interface tension can be predicted by the modified Szyszkowski equation.

Micellar Radii and High Aggregation Numbers in a 0.6 M NaCl Sodium Dodecylsulfate Solution Determined through Positron Annihilation Lifetime Spectroscopy

The equations related to a recently published method to measure both the micellar average radius (Rmic) and aggregation number (Nag) using a single technique, positron annihilation lifetime spectro...

Models of Micellar Structure Tested by SANS and SAXS (from a Kratky Camera) in Cesium Dodecyl Sulfate Solution

Small-angle neutron- (SANS) and X-ray-scattering (SAXS) patterns obtained at 40 °C from 0.0729 m D2O solution of cesium dodecyl sulfate (CsDDS) have been simultaneously evaluated in terms of the conventional two-shell model, a three-shell model created for demonstration purposes, and a newly developedand partly testedfour-component model. The simultaneous fitting is based on the fact that the two types of coherent scattering patterns differ only in the neutron- and X-ray scattering lengths. For comparison, the SANS and SAXS patterns were evaluated separately, too. In contrast to the two- and three-shell models, the four-component model is able to represent the continuously varying spatial distribution of the scattering contrast. From the results, it seems that the most reliable data are obtained from fitting the four-component model simultaneously to both patterns. Along with (approximate) core- and counterion profiles, application of the latter model can result in the spatial distribution of the solvent ...

Micelle and solvent relaxation in aqueous sodium dodecylsulfate solutions.

Dielectric spectra have been measured for aqueous sodium dodecylsulfate (SDS) solutions up to 0.1 mol L-1 at 25 degrees C over the frequency range 0.005 < or = nu GHz-1 < or = 89. The spectra exhibit two relaxation processes at approximately 0.03 GHz and 0.2 GHz associated with the presence of micelles in addition to the dominant solvent relaxation process at approximately 18 GHz and a small contribution at approximately 1.8 GHz due to H2O molecules hydrating the micelles. Detailed analysis reveals that the micelles bind 20 water molecules per SDS unit, but not as strongly as trimethylalkylammonium halide surfactants do. The relaxation times and amplitudes of both micelle relaxation processes can be simultaneously analysed with the theory of Grosse, yielding the effective volume of a SDS unit in the micelle and the lateral diffusion coefficient of the bound counterions. The findings of this investigation fully corroborate recent molecular dynamics simulations on structure and dynamics of SDS micelles.

Second harmonic generation from insoluble films of a rhodamine dye at the air–water interface: effect of sodium dodecylsulfate

The second harmonic generation (SHG) from the insoluble monolayers of bis-( N-ethyl, N-octadecyl)rhodamine perchlorate (RhC 18) formed on the surface of sodium dodecylsulfate (SDS) solutions of different concentrations has been studied. An enhancement of the second harmonic response was observed in the mixed films of RhC 18/SDS compared to the pure-dye layer. To clarify the origin of the phenomenon, the films were characterized by surface pressure–area isotherm and reflection–absorption spectroscopy studies. The analysis of surface pressure–area isotherms of RhC 18/SDS layers showed that incorporated SDS molecules essentially influence the rheological properties of the dye monolayer. The film parameters, such as the molecular surface area, maximum surface pressure, and solid-condensed phase composition, are the functions of SDS bulk concentration. A joint analysis of the SHG results and the reflection–absorption spectra revealed that the structural ordering within films was responsible for the enhancement of the nonlinear optical response, whereas the contributions from the spectral shifts and increased absorption upon aggregate formation are of less importance.

Small-Angle Neutron Scattering Study of Micelle Structure in Protein-Detergent Complexes

Small-angle neutron scattering measurements have been carried out on micellar solutions of the detergent sodium dodecyl sulfate (SDS) and its complexes with the protein Bovine Serum Albumin (BSA) in aqueous solutions. It is found that the structure of micelle-like clusters bound to the protein in protein-detergent complexes is different from that of normal micelles in the pure detergent solutions. In protein-detergent complexes, the micelle-like clusters tend to be spherical with a much smaller aggregation number (detergent molecules per micelle) than those in normal micelles, and they are independent of the shape and aggregation number of the micelles in the corresponding pure detergent solutions.

Rate of free-radical oxidation of C18 diene and triene fatty acids in aqueous micellar solutions and effectiveness of beta-carotene as an inhibitor of their oxidation.

The rate of accumulation of conjugated dienes of polyunsaturated fatty acids was measured during free-radical oxidation of linoleic acid (18:2n-6, LA), alpha-linolenic acid (18:3n-3, alpha-LNA), and gamma-linolenic acid (18:3n-6, gamma-LNA) initiated by 2,2;-azo-bis-(2-amidinopropane) hydrochloride in aqueous micellar solutions of sodium dodecyl sulfate and sodium cholate. It was shown that, unlike homogeneous solutions, the oxidative stability of PUFAs in aqueous dispersions increased with an increase in the extent of unsaturation. The rate of LA oxidation was more than tenfold greater than that of alpha- and gamma-LNA. The antioxidant activity of beta-carotene, in contrast to homogeneous solutions, in both micellar systems studied depended on the degree of PUFA unsaturation. We found that 5 micro M beta-carotene effectively inhibited the LA oxidation (almost by 90%), whereas the oxidation of alpha-LNA and gamma-LNA was not inhibited by beta-carotene even at much greater concentration (30 micro M). The paradoxical discrepancy between the extent of unsaturation and the PUFA oxidation rate, as well as a decrease in the efficiency of beta-carotene-dependent inhibition of oxidation of more polyunsaturated fatty acids in reactions conducted in aqueous dispersions is consistent with the model according to which the peroxyl radicals of LA and fatty acids with the double-bond number greater than two exhibit different polarity.

Beneficial reuse of chicken feathers in removal of heavy metals from wastewater

Natural and chemically treated chicken feathers (CF) were tested for their ability, as adsorbents, to remove copper and zinc from wastewater. Alkaline solutions of 0.2 N NaOH were found to be the best for the sorption process and a 0.6 wt% solution of dodecyl sulfate, as anionic surfactant, also gave best adsorption results. Treatment of CF with alkaline solutions adsorb more metal ions than those treated with the anionic surfactant followed by the untreated CF. Generally, the kinetics of the removal process by all tested sorbents was fast. The Freundlich isotherm model was found to represent the equilibrium results, of all adsorbents toward copper and zinc, reasonably well.

A modified dot-blot method of protein determination applied in the tannin-protein precipitation assay to facilitate the evaluation of tannin activity in animal feeds

Tannins have received considerable attention from animal nutritionists as potential agents for modifying ruminal fermentation patterns, or for exploring new feed resources. This group of secondary plant compounds is defined by their ability to form complexes with proteins. A widely accepted method for assaying the biological activity of extracted tannins is the precipitation of bovine serum albumin. The protein carries a radioactive label (125I) to allow direct quantification from the precipitate. Tannin–protein complexes dissolve in sodium dodecylsulfate solution. A dot-blot assay for protein determination, which is based on the reversible binding of a fluorochrome, benzoxanthene yellow, to the protein spots and is not disturbed by the presence of detergents, can replace the radioactive method by a fluorimetric measurement. A novel alternative to the last part of the dot-blot assay is to scan the stained protein spots in situ using a video camera and computer image analysis. Several filter sets were tested and, within a concentration range of 0·1–2·0 mg protein/ml, each of them yielded results identical to the original method while the time required was only 30 % of the working time consumed by the original procedure. The modified dot-blot assay should be applicable to the evaluation of tannin activity in all shrub and tree foliages considered as animal feed.