Cetyltrimethylammonium Bromide System Research Articles

Affinity based reverse micellar extraction and purification of bromelain from pineapple (Ananas comosus L. Merryl) waste

Affinity based reverse micellar extraction and separation (ARMES) technique is employed for the first time to extract and purify bromelain from pineapple (Ananas comosus L. Merryl) waste. The reverse micellar system of cetyltrimethylammonium bromide (CTAB)/isooctane/butanol/hexanol and sodium bis(2-ethyl-1-hexyl) sulfosuccinate (AOT)/isooctane is used for forward and reverse extractions respectively, with concanavalin A (Con A) as an affinity ligand. The effect of various process parameters like concentration of Con A during forward extraction, type of counter ligand and its concentration during back extraction, type of surfactants and its concentration, aqueous phase pH for reverse extraction on the purification and activity recovery of bromelain has been studied in detail. The optimized conditions of extraction resulted in purification of 12.32 fold with an activity recovery of 185.6%, which is higher than that reported for conventional reverse micellar extraction (RME). The forward, back, reverse and overall extraction efficiencies were found to be 49%, 44%, 48% and 14% respectively under optimized conditions.

A resonance light scattering amplification system for determination of trace amounts of benzidine in surface water

In this contribution, a novel resonance light scattering (RLS) amplification system was developed based on the enhanced RLS signals of the ammonium molybdate (AM)–cetyl trimethyl ammonium bromide (CTMAB) system upon the addition of benzidine (BD). It was found that in the presence of CTMAB, trace amounts of BD in surface water induced a remarkable change in RLS intensity of the AM–CTMAB system. Moreover, in the range of 0.005–1.0 μg mL−1, there was a good linear relationship between the enhanced RLS intensity and the concentration of BD with a detection limit of 0.08 ng mL−1. Three kinds of surface water sample were determined by this assay, and the interaction mechanism between AM and BD as well as several influencing factors were also investigated. Compared with conventional assays for the determination of BD in water, this assay has the advantages of simplicity, high sensitivity and it is more suitable for the determination of trace amounts of micromolecules.

Rheo-NMR studies of a nematic worm-like micelle system in a high-shear-rate regime

Deuterium NMR spectroscopy has been used to study the director dynamics of the nematic liquid-crystal system cetyl trimethylammonium bromide (CTAB)/D2O under the action of applied viscous torques. Shear forces were applied using a custom-built Couette cell that was introduced into an NMR superconducting magnet so that its rotational axis was parallel to the magnetic field direction, along which the liquid-crystal director originally aligned. Subsequently, a series of experiments was undertaken in which the inner cylinder of the cell was rotated continuously, at different rates, using a stepper motor. Above a threshold shear rate it was found that the director of the entire sample reoriented until a steady-state orientation was reached, the value of which depended on the average applied shear rate. These experiments revealed the presence of two distinct regimes. At the lower shear rates used, the observed behaviour was successfully captured by modelling the competition between the applied viscous torque and magnetic terms, and, upon cessation of shear the resultant spectra evolved during the relaxation of the director orientation in a way that simply mirrored those observed after the initiation of shearing. However, upon increasing the shear rate further, another regime was found in which the time evolution of the spectra towards the steady state was clearly not the simple reverse of that observed during relaxation. It is hypothesised that at these faster shear rates the relevant timescale of induced reorientation becomes short compared with the characteristic timescale of the thermally-activated scission and recombination of the micelles. As such, shear forces in this regime not only reorient micelles but also provide a novel mechanism for micelles to reach the steady state reorientation via the “disassembly” of micelles. The time evolution of the angular distribution function of the director orientation was extracted in these cases via fitting of the complex experimental spectra using a genetic algorithm and indeed shows that while a proportion of micelles appear to simply reorient as intact entities, as seen at lower rates, a distinct population circumvent this route, appearing more rapidly at the steady state orientation.

Changing micellar order, lever rule behavior and spatio-temporal dynamics in shear-banding at the onset of the stress plateau

Rapid 2D NMR velocimetry and 2H spectroscopy was used to investigate the spatio-temporal flow dynamics of the wormlike micelle system cetyltrimethylammonium bromide and sodium nitrate in a cylindrical Couette device. The nonlinear rheological response of this system exhibits a stress plateau indicative of shear banding. At the onset of the stress plateau, we observed an evolution with increasing applied shear rate from a situation where the shear rate in the high shear band increases while the interface position remains stationary to the classic lever rule behavior. This transition corresponds to increasing micellar ordering and changing fluctuating dynamics.

Study of Enhanced Chemiluminescence of Diperiodatocuprate (III) on 1,10-Phenanthroline/Hydrogen Peroxide/Cetyltrimethylammonium Bromide System

In the paper, a chemiluminescence (CL) system was developed based on the catalytical effect of diperiodatocuprate (III) (DPC) on the 1,10-phenanthroline (phen)/hydrogen peroxide (H(2)O(2)) in the presence of cetyltrimethylammonium bromide (CTAB). The effects of experimental conditions were investigated. Meanwhile the increase of CL intensity of the DPC/phen/H(2)O(2)/CTAB system is proportional to the concentration of phen in the range of low concentration. The linear range of the calibration curve is 5.0 × 10(-9)-1.0 × 10(-6) mol L(-1), and the corresponding detection limit is 1.9 × 10(-9) mol L(-1). The effects of phenolic compounds (PCs) on the system were investigated. Hydroquinone was used as an example to investigate the application of the CL system to the determination of PCs. The quenched CL intensity is linearly related to the logarithm of concentration of hydroquinone. The linear range of the calibration curve is 2.5 × 10(-9)-1.0 × 10(-5) g mL(-1), and the corresponding detection limit is 1.8 × 10(-9) g mL(-1). This phen and hydroquinone can be synchronously determined. The method was applied to the determination of hydroquinone in water samples and the recoveries were from 92% to 106%.

Determination of Trace Bi(Ⅲ) in Environmental Water Samples with Alizarin Red-Bi(Ⅲ)-CTMAB System by Resonance Light Scattering Spectroscopy

In hydrochloric acid solution with pH=4.1,Bi(Ⅲ) can react with alizarin red(AR) and cetyltrimethylammonium bromide(CTMAB) to form ternary ion-association complexe particles(the combination proportion was defined as n(Bi(Ⅲ)):n(AR) :n(CTMAB)=1:3:3).In this case,the resonance light scattering(RLS) intensities are enhanced greatly.The maximum RLS wavelength locates at 364 nm.The optimal conditions of the reaction,influence factors and the effect of coexisting substances were investigated.In addition,the reaction mechanism of the ternary ion-association complex was discussed.Under the optimal experimental conditions of 2.5 mL 1.0×10-4 mol/L alizarim red and 2.0 mL 1.0×10-4 mol/L CTMAB,the resonance scattering intensity(ΔI364 nm) was linearly related to the concentration of Bi(Ⅲ) in the range of 0～0.384 mg/L with a detection limit of 5.898×10-8 g/L.The method can be applied to the determination of Bi(Ⅲ) in water samples.The result was satisfactory and the recoveries were 99.5%～100.2% at the concentrations ranging from 0.552 to 0.831 μg/L,and the relative standard deviation was less than 2.7%.A sensitive,simple and new resonance light scattering method for determination of trace amount of Bi(Ⅲ) in environment was set up using the alizarin red as a spectrum probe.

Synthesis, characterization and enhanced electrical properties of CTAB-directed polyaniline nanoparticles

Inverse microemulsion system of cetyltrimethylammonium bromide (CTAB) molecules is utilized for virtually monodispersed and controlled growth of HCl polyaniline (PANI) nanoparticles at room temperature (ca. 300 K). The templated electroconductive polymer reveals lamellar crystalline structure under X-ray diffraction signifying marked sub-chain alignment of the polymerized nanoparticles. The nanostructured polymer has spherically symmetric morphology in a size range of 2.0 nm to 6.0 nm under electron microscope examination. Gel permeation chromatography gives polydispersity index of 1.02 for nanostructured polymer in agreement with the size monodispersity transpired by electron microscopy. The d.c. electrical conductivity σ dc of PANI at room temperature is 10.11 S/cm whereas the variation of conductivity with temperature in the range 227–303 K reveals that the conducting mechanism can be considered as three-dimensional variable-range-hopping (3D-VRH). UV-Vis spectrum indicates two broad absorption bands due to polaron formation that contributes to enhanced electrical conductivity of the polymer. The fundamental absorption edge in the polymer is formed by direct allowed transitions to the extent that the optical band gap value was found to be 2.35 eV. The crystalline nanostructure and homogeneous doping attained in the cationic template of amphiphile are argued as contributing factors to the enhanced conductivity of the polymer.

Multi-technique approach on the effect of surfactant concentrations on the thermal unfolding of rabbit serum albumin: Formation and solubilization of the protein aggregates

Effect of cationic surfactant, cetyltrimethylammonium bromide (CTAB) addition on the thermal denaturation of rabbit serum albumin (RSA) has been studied by employing small-angle neutron scattering (SANS), circular dichroism (CD), intrinsic fluorescence and ultra violet (UV) spectroscopy. The studies were performed at three different temperatures viz., 30, 50 and 70 °C and at two different concentrations of CTAB: the low concentration of CTAB used was 1 mM and the higher concentration was 80 mM (for SANS) and 20 mM (for CD, fluorescence and UV). A collective effect of high temperature and low concentration of CTAB led to the protein aggregation followed by solubilization of these aggregates at higher concentration of surfactant. At 1 mM CTAB and 30 °C, the protein–surfactant complex has a prolate ellipsoidal shape with semi-major axis of 88.9 Å and semi-minor axis of 19.6 Å which are slightly greater than the values of the native RSA. At 50 °C, the size of the semi-major axis increases while at 70 °C an increase in the size of both axes was found. The thermal outcome at higher concentration of CTAB (80 mM) was rather different. Higher concentration of CTAB unfolds the protein by the formation of micelle-like aggregates along the polypeptide chains of the protein and the complex was stabilized at higher temperatures, which was not found with lower concentration of CTAB. The CD results were found to be consistent with the SANS results, i.e., decrease in α-helicity of RSA was more when less amount of surfactant was present as compared to the system with higher surfactant concentration. In a similar fashion, results of relative fluorescence intensity (RFI) reveal that increase in temperature causes decrease in λ max of native RSA as well as RSA + 1 mM CTAB, whereas the λ max remains unchanged for RSA + 20 mM CTAB systems. That means the structure remains compact in presence of 20 mM CTAB while the structure becomes loose when low or zero amount of surfactant was present. The UV results indicate that the protein aggregation takes place in presence of low amount of CTAB and these aggregates become soluble at high concentration of CTAB.

Determination of trace selenium by differential pulse adsorptive stripping voltammetry at a bismuth film electrode

The differential pulse adsorptive stripping voltammetric behavior of selenium (IV)–p-aminobenzene sulfonic acid–cetyltrimethylammonium bromide system at a bismuth-coated glassy carbon electrode (BiFE) has been investigated. A well-defined and sensitive stripping peak of the selenium (IV)–p-aminobenzene sulfonic acid complex was observed at −0.76 V (vs. SCE) in a 0.15 mol/L acetate solution (pH 2.9) at a deposition potential of −0.40 V (for 120 s). The linear range was 2–30 μg/L and the detection limit for an accumulation time of 300 s was 0.1 μg/L. This method was applied to determine the trace amount of selenium in the samples.

Study on the enhanced fluorescent spectrum of ciprofloxacin+Al(III)+La(III)+cetyltrimethylammonium bromide system and its application

The fluorescence of ciprofloxacin (CIP) in HAc-NaAc buffer solution and the presence of cetyltrimethylammonium bromide (CTMAB) enhanced visibly with adding Al(III) and La(III). This enhanced fluorescence spectra were studied, and a new co-luminescence system of CIP+Al(III)+La(III)+CTMAB was discovered. There was a linear relationship between the enhanced fluorescence intensity and the concentration of CIP in the range of 0.50-80.2microgl(-1) under the optimized condition. A novel enhanced fluorescence method for the determination of trace CIP was established by using this co-luminescence system. The detection limit of the proposed method was 0.17microgl(-1) for CIP. This method is simple, rapid and sensitive. The CIP in milk samples were analyzed by the proposed method with satisfactory results. The relative standard deviation and the recovery were in ranges of 3.21-4.34% and 97.1-100.1%, respectively. The mechanism of the co-luminescence reaction and the reasons for fluorescence enhancement has been discussed.

A comparative study of transformation of micellar structures in CTAB and TTAB binary systems using Positron Lifetime Spectroscopy

AbstractThe micellar structures of cetyl‐tri‐methyl ammonium bromide (CTAB) and its homologues have been investigated employing several conventional techniques. However, due to lack of sensitivity inherent in these techniques and the perturbation introduced by the probe, the detailed structures of the aggregates in the so‐called single phase regions of these systems are far from being fully understood. Positron has been found to be a useful non‐destructive probe for investigating micellar structures in surfactant systems [1‐3] The present study is an effort to get a better insight into the micellar structures and their transformations in CTAB and TTAB aqueous binary systems Positron lifetime spectroscopy has been employed to study these systems covering a wide range of surfactant concentrations. A comparative study of the results obtained for the two surfactant systems have been discussed in this paper. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Direct synthesis of porous/hollow magnesium carbonate hydroxide spindly nanorods and their application in water treatment

Spindly Mg 5(CO 3) 4(OH) 2·4H 2O nanorods with porous and hollow nanostructures were synthesized in a water-in-oil reverse microemulsion system of cetyltrimethylammonium bromide (CTAB)/water/cyclohexane/ n-pentanol. These nanorods were characterized by a number of physical techniques, including powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). Comparison experiments showed that fundamental experimental parameters, such as the molar ratio of H 2O to CTAB and the concentration of reactants, were important in the morphological control of Mg 5(CO 3) 4(OH) 2·4H 2O nanostructures. The potential applications of the as-synthesized Mg 5(CO 3) 4(OH) 2·4H 2O nanorods in water treatment were also investigated.

Adsorption equilibria between dye and surfactant in single and binary systems onto geological materials

Abstract Adsorption characteristics of cationic dyes and surfactants onto clay and sandstone from a single component system were studied using toluidine blue (TB) and cetyl trimethylammonium bromide (CTAB). Equilibrium data of TB and CTAB in the single solute systems fit well to the Langmuir and the Freundlich adsorption isotherms. Competitive adsorption was observed between dye and surfactant cations. The effect of sodium chloride on dye and surfactant adsorption was studied in TB–NaCl and CTAB–NaCl binary systems. Equilibrium adsorption for binary systems was analyzed by using the extended Langmuir and the extended Freundlich models. Adsorption results for the TB–CTAB system onto both adsorbents were also well described by the Sheindorf–Rebuhn–Sheintuch (SRS) model for multi-component systems. Free energy changes for adsorption systems were calculated using thermodynamic equilibrium constants evaluated from selectivity coefficients of the binary systems. The site distribution functions estimated using Freundlich model parameters gave valuable information about the ratio of the adsorption sites on adsorbent surface having different affinity for competing cations.

A facile route to design pH-responsive viscoelastic wormlike micelles: Smart use of hydrotropes

A simple and effective route to design pH-responsive viscoelastic wormlike micelles based on commercial compounds is reported. According to this route, pH-sensitive viscoelastic fluids can be easily obtained by introducing a pH-responsive hydrotrope into a surfactant solution. In this paper, the mixed system of cetyltrimethylammonium bromide (CTAB) and potassium phthalic acid (PPA) was studied in detail. This pH-sensitive fluid can be switched between a gellike state and a waterlike state within a narrow pH change. Rheology and DLS results revealed that the pH-sensitive flowing behavior was attributed to the microstructure transition between wormlike micelles and short cylindrical micelles. Combined with fluorescence anisotropy, NMR, and UV–vis, it was demonstrated that the pH response of viscoelastic fluid originated from the different binding abilities of hydrotrope to surfactant as pH varies. Furthermore, different kinds of hydrotropes can be utilized to prepare pH-responsive viscoelastic fluids in the desired pH areas.

PH-Regulated Molecular Self-Assemblies in a Cationic−Anionic Surfactant System: From a “1−2” Surfactant Pair to a “1−1” Surfactant Pair

With the aid of pH variation, direct transformation of a "1-1" cationic-anionic surfactant pair to a "1-2" cationic-anionic surfactant pair was attained in the system of cetyltrimethylammonium bromide and n-decylphosphoric acid. Owing to the transformation of a "1-1" pair to a "1-2" pair, diverse microstructures and peculiar phase behavior in this cationic-anionic surfactant mixture was obtained at different pH. It is proposed that pH can be manipulated for effectively tailoring the self-assembled organization in this cationic-anionic surfactant system, including spherical micelle, wormlike micelle, vesicle, and lamellar structure. In contrast to the conventional "1-1" surfactant pair, the "1-2" cationic-anionic surfactant pair exhibits unexpectedly weak aggregating ability. It is suggested that the hydrated volume of surfactant headgroup should be taken into consideration to better elucidate the self-assembly behavior of these "1-2" cationic-anionic surfactant mixtures.

A LB film morphological study with reference to biopolymer–surfactant interaction taking gelatin–CTAB system as a model

The interaction of gelatin with cetyltrimethylammonium bromide (CTAB) studied at pH 9 and an ionic strength of 0.005, produces an interfacial surface active gelatin–CTAB (monomer) complex (GS n I), a surface inactive gelatin–CTAB (micelle) complex in bulk (GS m B), followed by coacervation, and its solubilization in micellar solution of CTAB. We have herein attempted to probe the interfacial morphological changes of gelatin and its CTAB complexes, and not the bulk properties like coacervation and/or micellar solubilization. The morphologies of pure gelatin and CTAB films and that of gelatin–CTAB interacted complex at the interface have been investigated using LB, SEM, AFM and ellipsometric techniques. The stability of the gelatin monolayer at varied concentrations with and without CTAB has been examined. The SEM images of stabilized films of gelatin and gelatin–CTAB complex have witnessed compact smooth as well as rough surfaces with formation of distinct domains. Drastic morphological change in the film before the critical aggregational concentration of CTAB (T 2) has been in line with an initial abrupt decrease in surface tension. This has been corroborated by AFM measurements, which along with morphology demonstration has provided information on the diameter of the ensembles formed and roughness of the LB films constituted of pure components and their complexes. Thickness of the film was at its maximum in the domain region, as corroborated by ellipsometric technique. Such an elaborate interfacial monolayer and film morphology study of biopolymer-amphiphile system has been rarely documented in literature.

Fluorescence enhancement effect for the determination of DNA with calcein–cetyl trimethyl ammonium bromide system

A new spectrofluorimetric method was developed for the determination of trace amounts of DNA using the calcein as a fluorescent probe. In the presence of appropriate amounts of the cationic surfactant cetyl trimethyl ammonium bromide (CTAB), the anionic dye calcein dimerizes. The weak fluorescence intensity of the dimer was enhanced by adding DNA at pH 6–7. The interaction between calcein–CTAB and DNA was studied on the basis of this behavior and a new method was developed for determining DNA. Under the optimal conditions, the enhanced fluorescence intensity was in proportion to the concentration of DNA in the range of 4.0 × 10 −6 to 8.0 × 10 −5 g L −1 for fsDNA and thermally denatured ctDNA (4.5 × 10 −6 to 9.0 × 10 −5 g L −1). The detection limits (S/N = 3) were 2.0 × 10 −6 and 2.2 × 10 −6 g L −1, respectively. This method was used for determining the concentration of DNA in synthetic samples with satisfactory results.

Synthesis of ZnO–SnO2 nanocomposites by microemulsion and sensing properties for NO2

Nanocrystalline ZnO–SnO2 composites as NO2 gas sensor materials have been successfully synthesized through a reverse microemulsion method for controlled grain size and morphology. This method was to create a water-in-oil (W/O) microemulsion that contained a minimal amount of surfactant and a maximum amount of water. Pseudo-ternary phase diagrams in the quaternary microemulsion system of cetyltrimethylammonium bromide (CTAB), n-pentanol, n-octane, and water (or aqueous solution of precursor salts) were presented and the effects of the alcohol chain length, the ratio of CTAB to alcohol or water, and the precursor salt concentration on the formation and stability of microemulsions were studied. The performance and structure of the nanocomposites synthesized with the optimal parameters in the phase diagrams of the microemulsions were characterized by Brunauer–Emmett–Teller (BET) specific surface measurement, transmission electron microscopy (TEM), and X-ray diffraction (XRD), and the gas sensing properties were examined. The experimental results showed that these nanocomposites were highly sensitive and selective for the detection of NO2 and CO, and the sensor response depended on the composition of the composites, calcination temperature, operating temperature and gas concentration in air. Their sensing performance was further enhanced through introduction of a small amount of metals or other oxides as dopants or surface coatings. The gas-sensing mechanism of the nanocomposites was discussed by temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopic (XPS) analysis and was attributed to chemical and electronic synergistic effects between the nanocomposites and the gases.

Improved activity of enzymes in mixed cationic reverse micelles with imidazolium-based surfactants

This work reports the significant enhancement in performance of interfacially active enzymes, Chromobacterium viscosum (CV) lipase and horseradish peroxidase (HRP) in mixed reverse micelles of cetyltrimethylammonium bromide (CTAB) and imidazolium-based amphiphiles having varying tail lengths. Lipase activity in these mixed systems was always higher than that in the individual cationic reverse micelles of CTAB or any imidazolium surfactant, highest being observed in the mixed system of CTAB (50 mM) and 6 (1-tetradecyl-3-methyl imidazolium bromide, 40 mM)/water/isooctane/ n-hexanol (0.24 M), second-order rate constant, k 2 = 1301 ± 5 cm 3 g −1 s −1, ∼200% higher compared to that in CTAB and ∼65% more than the most popular AOT-microemulsion. Activity increased with concentration of imidazolium surfactant and also with its alkyl tail length. To have a more profound view on the structure–activity relationship, CTAB was replaced by cetyltriethylammonium bromide (CTEAB) and cetyltripropylammonium bromide (CTPAB) with subsequent increase in the headgroup size. The generalized influence of these mixed cationic systems on surface-active enzyme was also verified using HRP, where the activity improved ∼100%. This enhancement in enzyme activity is presumably due to the activating effect of the imidazolium cation in the enzymatic reactions by improving the nucleophilicity of interfacial water in vicinity of enzyme through hydrogen bonding.

Lyotropic liquid crystalline phases in a ternary system of 1-hexadecyl-3-methylimidazolium chloride/1-decanol/water

Lyotropic liquid crystals formed in a ternary system of 1-hexadecyl-3-methylimidazolium chloride ([C16mim]Cl), 1-decanol, and water at 25 degrees C are reported. The hexagonal and lamellar phases were characterized by small angle X-ray scattering and polarizing optical microscopy. In the phase diagram, the system shows two isotropic liquid phases, a hexagonal phase connected to the [C16mim]Cl-water axis, and a lamellar phase in the center. The formation of liquid crystalline phases is believed to arise from a hydrogen-bonded network comprised of an imidazolium ring, anion, 1-decanol, and water. In the liquid crystal, the intercalation of 1-decanol between neighboring [C16mim]Cl molecules favors the appearance of lamellar phases. The phase behavior of the present system is discussed in comparison with a similar ternary system of cetyltrimethylammonium bromide (CTAB).