Addition Of CTAB Research Articles

Catalytic effect of supported metal ion complexes on the induced oxidative degradation of pyrocatechol violet by hydrogen peroxide

Kinetics of the oxidative degradation of pyrocatechol violet dye (PCV) {2-[(3,4-dihydroxyphenyl)(3-hydroxy-4-oxocyclohexa-2,5-dien-1-ylidene) methyl]-benzenesulfonic acid} by H 2O 2 catalyzed by supported transition metal complexes have been studied. The reaction was followed by conventional UV–vis spectrophotometer at λ max=440 nm in a buffer solution at pH 5.1. The supports used were silica gel and cation exchange resins (Dowex-50W, 2 and 8% DVB), while the complexes were [Cu(amm) 4] 2+, [Cu(en) 2] 2+, [Cu(ma) 4] 2+, [Co(amm) 6] 2+, and [Ni(amm) 6] 2+ (amm=ammonia, en=ethylenediamine, and ma=methylamine). The reaction exhibited first-order kinetics with respect to [PCV] and [H 2O 2]. The reactivity of the catalysts is correlated with the redox potential of the metal ions, the type of support, and the amount of supported complexes. The rate of the reaction increases with increasing pH and the addition of NaCl. Addition of SDS and CTAB showed inhibiting effects. The reaction is enthalpy-controlled as confirmed from the isokinetic relationship. A reaction mechanism involved the generation of free radicals as an oxidant has been proposed.

Ultrafiltration characteristics of colloid solutions containing oxyethylated methyl dodecanoate, hexadecyltrimethylammonium bromide and selected phenols as pollutants

The effect of hexadecyltrimethylammonium bromide upon ultrafiltration of oxyethylated methyl dodecanoate solutions and separation of phenol, 4-nitrophenol and 4-methylphenol was investigated. The permeate fluxes and the resistance of the secondary layer (SL) were determined and the effect of the surfactant discussed. The rejection of the phenols, distribution and binding constants were determined and interpreted. It was found that colloidal systems containing mixtures of oxyethylated methyl dodecanoates and hexadecyltrimethylammonium bromide are advantageous systems for recovery of phenols by micellar enhanced ultrafiltration (MEUF). An addition of CTAB causes only a slight increase in the resistance of the SL and a slight decrease in the ultrafiltration flux. This negative effect is fully compensated for by improved rejections of phenols, observed in mixed surfactant systems.

Improved Flow Injection Analysis of H2O2 on Cinder/Prussian Blue‐Modified Electrodes by CTAB Micelles

AbstractIn the present work, a new strategy involving the addition of CTAB at its critical micelle concentration was developed to improve the electrochemical properties of the cinder/PB‐modified screen‐printed electrode (designated as cinder/PB‐SPE) in the detection of H2O2 by flow injection analysis (FIA). Such new PB hybrids derived from cinder have remarkable stability even under strong hydrodynamic stress. The cylindrical CTAB micelles formed at the 2nd critical micelle concentration can effectively promote the PB redox behavior. Under optimized conditions with pH 7 PBS + 7 mM CTAB as carrier solution in FIA, a linear calibration was obtained up to 25 μM H2O2 with slope, regression coefficient, and detection limit (S/N = 3) of 1.03 A/Mcm2, 0.995, and 4.02 μM respectively. Interferences by direct electrochemical oxidation of easily oxidizable substances can be prevented due to the low detecting potential of the working system.

Binding of hexadecyltrimethylammonium bromide to starch polysaccharides. Part I. Surface tension measurements

Surface tension measurements were used to characterise the binding of the cationic surfactant hexadecyltrimethylammonium bromide, CTAB, to three starch polysaccharides, amylose from potato, amylopectin from potato and amylopectin from barley. Surface tension measurements were used according to the axisymmetric drop shape analysis, ADSA, to determine the concentration of free CTAB monomers during consecutive addition of CTAB to the polysaccharide solutions. The interaction between the starch polysaccharides and CTAB was studied at three starch concentrations, 0.1, 0.25 and 0.5% (w/w). Binding isotherms were derived from the concentration of free CTAB and the type of binding was determined with Scatchard plots. The binding capacities of CTAB correlated linearly with the polysaccharide concentration but were independent of the type of starch polysaccharide. All three starch polysaccharides were able to bind 33 mmol CTAB per mole glucose units. The binding of CTAB to amylose was cooperative while the binding of CTAB to amylopectin was of Langmuir type.

Preparation of Cuprous Oxide Particles of Different Crystallinity

Both the cubic single crystals and the spherical polycrystals of cuprous oxides (Cu2O) were prepared by the reduction of aqueous CuSO4, with hydrazine as a reductant in the presence of different organic molecule additives, such as hexadecyltrimethyl ammonium bromide (CTAB), glucose (C6H12O6), ethylene glycol (C2H6O2), and glycerol (C3H8O3), at room temperature. It was found that the organic additives added had an important influence on the formation mechanism of the Cu2O particles and could lead to different microstructures of the resultant Cu2O crystallites. The addition of CTAB to the reaction solution could induce the formation of cubic Cu2O single crystals, while glucose resulted in the formation of spherical polycrystals. All the samples were characterized by X-ray powder diffraction and transmission electron microscope (TEM). TEM observations indicated that the nanosized primary particles formed immediately after the reactants were mixed, followed by the competition between diffusion of the reactive constituents and aggregation of the nanosized primary particles. In the presence of CTAB, the diffusion of the reactants was a major factor contributing to the single crystal morphology of the Cu2O products, while the aggregation of the primary nano-particles into polycrystallites prevailed when glucose existed in the reaction system.

Modification of the phosphoketolase assay for rapid identification of bifidobacteria

The phosphoketolase assay is commonly used as a definitive criterion for identification of bifidobacteria. A limitation of the assay is the time-consuming process of cell disruption, either by use of the French Pressure Cell or by sonication. We have replaced the time consuming cell disruption process with a more rapid cell membrane disruption process by pretreating cells with the detergent hexadecyltrimethylammonium bromide (cetrimonium bromide, CTAB). The effect of no pretreatment, sonication or the addition of CTAB (0.45 mg/ml) on color development in the phosphoketolase assay was tested using pure cultures of bifidobacteria and lactobacilli. No phosphoketolase activity was observed with bifidobacterial cultures without cell disruption or with lactobicilli that had undergone cell disruption. All bifidobacterial cultures gave a similar color formation whether sonication or CTAB addition was used to disrupt cells. Use of CTAB to disrupt cell membranes is an effective alternative to the time consuming traditional cell disruption procedures and increases the number of cultures that can be simultaneously assayed and presumptively identified using the phosphoketolase assay.

Rheological properties and microstructure of model processed cheese containing low molecular weight emulsifiers

AbstractThe influence of low molecular weight emulsifiers (SDS, CTAB, lecithin, mono‐diglycerides) on rheological properties and the microstructure of model processed cheese, made using rennet casein, at three different pH values was investigated. Interactions between the low molecular weight emulsifiers and rennet caseins in model processed cheese are consistent with those found in model food emulsions of liquid continuous phase. Compared with the control, the addition of CTAB (cationic) resulted in the hardest and most elastic processed cheese, while the incorporation of SDS (anionic) produced the softest and least elastic cheese. Processed cheese with added lecithin or mono‐diglycerides behaved much like the controls, but with an increase in syneresis level. No syneresis was observed with the SDS cheeses. In general, low pH cheeses (pH 5.45) were harder than high pH cheeses (pH 6.05). Rheologically, all the processed cheese samples can be described as [weak gels]. The protein matrix of the high pH processed cheese containing CTAB consisted mainly of protein particles linked into a chain‐like form, while those containing lecithin and SDS showed a mixture of individual as well as short chained protein aggregates, and the control had protein aggregates of intermediate size. The added low molecular weight emulsifiers resulted in a finer dispersion of the fat in the protein matrix. Protein‐emulsifier charge interactions seem to be the prime determinant of the rheological properties of these model processed cheeses.

Onset of Hydrophobic Attraction at Low Surfactant Concentrations

We report here on the interaction between silica surfaces in a range of CTA+ (cetyltrimethylammonium cation) concentrations up to the point of zero charge (5 × 10-5 M) in a background electrolyte (3 × 10-3 M sodium acetate). In the absence of CTA+ the static interaction is repulsive at all distances. The addition of CTAB up to 10-5 M has no effect on the interaction. Between 2 × 10-5 and 3 × 10-5 M the surface charge as deduced from interaction at large separations remains unchanged, but the interaction becomes attractive at distances less than a Debye length. The strength of the attraction increases several times as surfactant concentration increases to 4 × 10-5 M with simultaneous reduction in the electrostatic repulsion at larger distances. At 5 × 10-5 M the interaction is attractive at all distances. The results confirm that CTA+ adsorption is cooperative and nonlinear in concentration and is enhanced by surface proximity. Both effects lead to a long range hydrophobic force.

Single step method of preparation of detergent-permeabilized Kluyveromyces fragilis for lactose hydrolysis

β-Galactosidase activity of CTAB-permeabilized K. fragilis depends upon the cell to detergent ratio and the pH of the permeabilizing medium. Maximum β-galactosidase activity was observed when the cell to detergent ratio was 1:0·01 at neutral pH. A simple and single step method for the preparation of whole cell β-galactosidase is described which involves adjusting the pH of the growth medium at the beginning of the stationary phase to 7·0, addition of CTAB directly to the growth medium at 1% concentration of biomass (wet weight), before harvesting cells by centrifugation. This whole cell enzyme activity readily hydrolysed high concentrations of lactose in buffer and whey.

Fluorescence probe studies of bis(2-ethylhexyl) sodium sulfosuccinate (AOT) and AOT/cetyltrimethylammonium bromide (CTAB) systems

Steady-state and time-resolved techniques have been used to study the physicochemical properties of bis(2-ethylhexyl) sodium sulfosuccinate (AOT) and AOT/cetyltrimethylammonium bromide (CTAB) micellar systems. The aggregation number of the AOT micellar system was obtained by steady-state and time-resolved techniques. The variation of the aggregation numbers of the AOT micellar system with NaCl concentration was studied. All the results from the two methods showed that the aggregation numbers increased with NaCl concentration. The CMC values at which the spherical micelle changes to a rod-shaped micelle were obtained in AOT and AOT/CTAB systems. At the same time, the influence of NaCl concentration on the second CMC values was also investigated. Time-resolved fluorescence experiments showed that both the addition of CTAB to AOT and the addition of AOT to CTAB resulted in a large increase in the micelle aggregation number. In addition, we also studied the variation of the aggregation numbers of the AOT/CTAB solution system with temperature and NaCl concentration.

Stability of bilirubin oxidase in organic solvent media: A comparative study on two low‐water systems

The storage stability of bilirubin oxidase was studied in water-in-oil CTAB microemulsions with a chloroformrich continuous organic phase. The kinetics of the inactivation process were best described by a double exponential equation. Approximately half of enzymatic activity was lost during a "fast" phase with a half life of ca. 50 min, whereas the remaining activity was lost much more slowly (half life ca. 1000 min). Rates of inactivation were not affected significantly by variation of either solvent composition or concentration of water droplets, but inactivation was more rapid when droplet size was very small. Steady-state enzyme kinetics were studied at various stages in the inactivation process, and it was shown that inactivation occurred without change in the K(m) of the enzyme for bilirubin. Stability was also studied in a liquid/solid two-phase system; it was found that the inactivation process in this system; it was found that the inactivation process in this system was best described by a single exponential term. The rate was similar to the "fast" phase rate observed in the water-in-oil microemulsion system. Inactivation of the enzyme slow. Addition of the surfactant CTAB to the aqueous environment increased the rate of inactivation to levels comparable to those of the "slow" phase observed in water-in-oil microemulsions.

ChemInform Abstract: Micellar Effect on the Photosensitized Debromination of 2,3‐Dibromo‐3‐phenylpropionic Acid. Control of Forward and Back Electron Transfers.

AbstractThe photodebromination of (I) becomes faster on addition of the detergent CTAB.

Effect of micelle formation on the absorption spectra of a functionalized detergent with the anthraquinone moiety

Measurements of the absorption spectra of aqueous solutions of (2-anthraquinonylmethyl)dodecyldimethylammonium (AQD+) bromide have been performed. From the concentration dependence of the molar absorption coefficient at λmax= 330 nm (εapp), the c.m.c. and the molar absorption coefficient of AQD+ participating in its micelle formation were calculated by assuming a micellar pseudo-phase model. The change in εapp above the c.m.c. was found to be due to interactions of the anthraquinone moieties, by studying the effect of the addition of hexadecyltrimethylammonium bromide (CTAB) to the AQD+ micellar solution. The effect of the addition of CTAB to the AQD+ monomer solution was also examined, but the spectra of the AQD+ monomer were little affected by the addition of CTAB. Measurements of the absorption spectra of aqueous solutions of the monomeric AQD+ and sodium dodecylsulphate (SDS) point to the formation of a stable ion-pair complex between them. On further addition of SDS, the complex disappeared above the c.m.c. of SDS. This amphiphatic anthraquinone derivative serves as a probe for determining the c.m.c. of SDS in the absence and presence of electrolyte because the molar absorption coefficient at 290 nm changes by a factor of 7 above and below the c.m.c. of the host surfactant.

Regulatory aspects of permeation through ordinary and modified nylon films

Permeation through ordinary and modified nylon 66 films was studied in order to devise means by which the permeation rate could be regulated. Three types of film matrix were used: unmodified nylon film, nylon film where the amino end groups were blocked to about 75%, and nylon film with blocked amino groups (75%) where also a quaternary ammonium compound (cetyl trimethyl ammonium bromide, CTAB) was added to the film. The permeation rate of p-toluene sulfonate and β-naphthalene sulfonate through these films were studied with special emphasis on the pH dependence. Especially at high pH and in agreement with the higher partitioning to the film for naphthalene sulfonate, this salt gave a higher permeation rate than did toluene sulfonate. The permeation rate through unmodified nylon film varied with pH. The blocking of the amino groups decreased the pH dependence and addition of CTAB increased the level of the permeation rate within the whole pH range studied. Very low or high permeation rates could be achieved by means of different pHs in the water solutions on either side of the film.

Evaluation of viable counting procedures for the enumeration of sulfate-reducing bacteria in estuarine sediments

The recovery of known viable populations of sulfate-reducing bacteria belonging to the genera Desulfovibrio, Desulfobacter and Desulfobulbus from inoculated, sterile, anoxic estuarine sediments has been determined using Postgate's and Widdel's media. Recovery of Desulfovibrio populations was consistently higher with Postgate's medium, whilst Widdel's medium always yielded higher viable counts of Desulfobacter and Desulfobulbus. In all cases the average recovery after 5 days incubation at 4°C was only about 50% of the added viable cells. Two surface active agents, cetyl trimethylammonium bromide (CTAB, final concentration 0.00001% w/v) and sodium tripolyphosphate (NaPP, final concentration 0.0005% w/v), both increased recoveries of viable cells, with CTAB showing the greatest effect (16% increase). The addition of CTAB to untreated sediment samples also significantly increased the viable counts of in situ populations of sulfate-reducing bacteria, although the effect was more variable (0–200% increase). Viable counts of different types of sulfate-reducing bacteria from estuarine sediments, even using the most appropriate growth medium and in the presence of CTAB, grossly underestimate the in situ populations of these bacteria when compared with total direct counts and rates of sulfate reduction measured within the same sediment. The significance of viable counts of sulfate-reducing bacteria within sediments should therefore be interpreted with caution.

Coenzyme Models. IX. Micellar Catalysis of Isoalloxazine (Flavin) Oxidation of Dithiol

Abstract The influence of micelles on the reaction of isoalloxazines and 1,4-butanedithiol(BDT) was studied. The pKa of BDT was lowered by 0.3 pK unit in the presence of the hexadecyltrimethylammonium bromide(CTAB) micelle, indicating the formation of “hydrophobic ion pairs.” The apparent second-order rate constant for the reaction of 3-methyl-10-ethylisoalloxazine and BDT increased by 18-fold on addition of CTAB(3 mM). The UV-visible spectrum of 3-hexadecyl-10-butylisoalloxazine in the presence of the CTAB micelle was similar to that in organic solvents, the rate being enhanced by more than 400-fold as compared with that in a nonmicellar system. Anionic(SDS) and nonionic(Brij-35) micelles suppressed the reaction. The results show that the flavin oxidation of dithiol is facilitated by the environments of the CTAB micelle.