Cetyltrimethylammonium Bromide System Research Articles

Exploring the Impact of Cationic Surfactant Ctab on Bleu Brilliant G 250 De Cosmassie: Implications for Health Management and Environmental Sustainability

Background: Surfactants are ubiquitous in both natural and industrial processes due to their unique ability to reduce surface tension and facilitate interactions between hydrophilic and hydrophobic substances. Cationic surfactants like cetyltrimethylammonium bromide (CTAB) are of particular interest because of their widespread applications in areas such as healthcare and environmental management. The interaction between surfactants and dyes, such as Bleu Brilliant G 250 de Cosmassie, is critical in industrial processes, especially in the textile industry where wastewater treatment poses significant environmental challenges. Objective: The aim of this study was to explore the thermodynamic behavior of CTAB when combined with Bleu Brilliant G 250 de Cosmassie in aqueous solutions at room temperature. It sought to determine the critical micelle concentration (CMC) and the degree of counter-ion dissociation (α), and to calculate the changes in Gibbs free energy (ΔGm), enthalpy (ΔHm), and entropy (ΔSm) of the system. Methods: The study employed conductometric and spectrophotometric techniques to analyze the CTAB-dye interactions. Solutions were prepared with varying concentrations of CTAB and Bleu Brilliant G 250 de Cosmassie in deionized water, ensuring solvent purity through stringent conductivity and pH monitoring. Electrical conductance was measured at different temperatures to determine the CMC, while absorbance spectra were recorded to observe changes in the interaction between the surfactant and dye. The degree of counter-ion dissociation was calculated by the slope ratio method, and thermodynamic parameters were computed using established equations. Results: The conductometric studies revealed an increase in CMC with temperature, indicating a stabilization of surfactant monomers at higher temperatures. For CTAB and Bleu Brilliant system 1, the CMC was found to be 0.8 with α valued at 0.83. For system 2, the CMC values were 1.55 and 1.6 with α values of 1.01 and 0.91, respectively. Thermodynamically, the system displayed a Gibbs free energy of micellization of -33.09 KJ/mol, an enthalpy change of -6.53, and an entropy change of 0.1325 JK^-1 mol^-1. Conclusion: The study concluded that the interaction between CTAB and Bleu Brilliant G 250 de Cosmassie is influenced significantly by temperature, which affects the micellization behavior and thermodynamic properties. The findings contribute to a better understanding of the fundamental thermodynamic parameters influencing surfactant-dye interactions, providing insights that may improve industrial processes and environmental sustainability.

Fluorescence Quenching of Carbazole by Selected Phenols in a Cationic Micellar System of Cetyltrimethyl Ammonium Bromide (CTAB).

A group of selected phenols i.e., picric acid, p-Nitrophenol, m-Nitrophenol, o-Nitrophenol, and phenol interactions were studied with a fluorescent probe carbazole in a micellar system of CTAB. CTAB concentration was optimized for maximum quenching of carbazole for each studied phenol. Interaction was studied in 0.02 and 0.1mol/dm3 CTAB. All the studied phenols resulted in the quenching of carbazole in both CTAB concentrations though lower CTAB concentration was found optimum for highest quenching of the probe carbazole. Carbazole fluorescence quenching with phenols were explained with the help of Stern-Volmer equation that produced the constants of Stern-Volmer ([Formula: see text]). [Formula: see text] shows the sensitiveness of the method for the studied phenol and were observed in the order picric acid > phenol > m-Nitrophenol > p-Nitrophenol > o-Nitrophenol. Detection threshold (DT) and quantification threshold (QT) were observed in the order 1.76 [Formula: see text] 10-7- 6.30 [Formula: see text] 10-7mol/dm3 and 5.898 [Formula: see text] 10-7-2.11 [Formula: see text] 10-6mol/dm3 respectively. The method is reproducible and is effective for the determination of studied phenols in the samples.

Triple-stimuli-responsive hydrogels based on an aqueous mixed sodium stearate and cetyltrimethylammonium bromide system

Triple-responsive supramolecular hydrogels were prepared using sodium stearate (SS) and cetyltrimethylammonium bromide (CTAB) in water and physiological saline. Hydrogels can respond to stimuli such as temperature, pH, and CO2 and exhibit tunable rheological behaviors. The high Krafft point and low solubility of SS have prevented its use in many applications. The mixing of SS with the cationic surfactant CTAB decreases the Krafft point and increases the solubility of SS owing to the synergistic self-assembly of the two materials. The prepared hydrogels exhibited good thermosensitivity within the physiological temperature range. For CTAB/SS/H2O mixed systems with a constant molality of CTAB or SS, the gel-to-sol transition temperature increased as the molar ratio of SS to CTAB increased. Under certain conditions, the prepared hydrogels exhibited pH-responsive rheological behavior. The gel–sol transition could be repeated for three or more cycles by changing the pH. The hydrogels also exhibited CO2/N2 switchable behavior, and the gel–sol transition was realized for at least three cycles by alternately bubbling CO2 and N2 into the sample. Steady-state and dynamic rheological measurements,transmissionandreflection polarizingmicroscopy, transmission electron microscopy, dynamic light scattering, differential scanning calorimetry, Fourier-transform infrared spectroscopy, and molecular dynamics simulations were carried out to explore the multiple-stimuli-responsive mechanism of the prepared hydrogels. The molecular insights on the formation of hydrogels and their stimuli responses gained in this work may be helpful for the theoretical development of smart hydrogel systems. We hope that the multiple-stimuli-responsive hydrogels may have potential applications in fields such as sensors, controlled drug delivery, and cosmetics.

Interfacial Properties, Wettability Alteration and Emulsification Properties of an Organic Alkali–Surface Active Ionic Liquid System: Implications for Enhanced Oil Recovery

Combinatory flooding techniques evolved over the years to mitigate various limitations associated with unitary flooding techniques and to enhance their performance as well. This study investigates the potential of a combination of 1-hexadecyl-3-methyl imidazolium bromide (C16mimBr) and monoethanolamine (ETA) as an alkali–surfactant (AS) formulation for enhanced oil recovery. The study is conducted comparative to a conventional combination of cetyltrimethylammonium bromide (CTAB) and sodium metaborate (NaBO2). The study confirmed that C16mimBr and CTAB have similar aggregation behaviors and surface activities. The ETA–C16mimBr system proved to be compatible with brine containing an appreciable concentration of divalent cations. Studies on interfacial properties showed that the ETA–C16mimBr system exhibited an improved IFT reduction capability better than the NaBO2–CTAB system, attaining an ultra-low IFT of 7.6 × 10−3 mN/m. The IFT reduction performance of the ETA–C16mimBr system was improved in the presence of salt, attaining an ultra-low IFT of 2.3 × 10−3 mN/m. The system also maintained an ultra-low IFT even in high salinity conditions of 15 wt% NaCl concentration. Synergism was evident for the ETA–C16mimBr system also in altering the carbonate rock surface, while the wetting power of CTAB was not improved by the addition of NaBO2. Both the ETA–C16mimBr and NaBO2–CTAB systems proved to form stable emulsions even at elevated temperatures. This study, therefore, reveals that a combination of surface-active ionic liquid and organic alkali has excellent potential in enhancing the oil recovery in carbonate reservoirs at high salinity, high-temperature conditions in carbonate formations.

Interaction of sulphone based reactive dyes with cationic surfactant: a spectroscopic and conductometric study

Abstract Interaction of sulphone based reactive dyes, designated as dye-1 and dye-2, with cationic micellar system of cetyltrimethylammonium bromide (CTAB), has been investigated by spectroscopic and conductometeric measurements. Efficiency of the selected micellar systems is assessed by the values of binding constant (K b ), partition coefficient (K x ) and respective Gibbs energies. Critical micelle concentration (CMC) of surfactant, electrostatic and hydrophobic interactions as well as polarity of the medium plays significant role in this phenomenon. The negative values of Gibbs energies of binding (∆G b ) and partition (∆G p ) predicts the feasibility and spontaneity of respective processes. Similarly negative values of ∆G m and ∆H m and positive values of ∆S m , calculated from conductometeric data, further, revealed the exothermicity, spontaneity and, thus, stability of system. The results, herein, have disclosed the strong interaction between dye and surfactant molecules. The dye-2 has been observed to be solubilized to greater extent, as compared to dye 1, due to strong interaction ith hydrophiles of CTAB and accommodation of its molecules in palisade layer of micelle closer to the micelle/water interface.

Mixed Surfactant‐Based Reverse Micellar Extraction Studies of Bovine Lactoperoxidase

AbstractThe suitability of reverse micellar extraction for recovery of bovine lactoperoxidase (LP) from aqueous solution was evaluated using systems formed by ionic and nonionic surfactant mixtures. The influence of ionic surfactant concentration, organic solvent, and pH on the extraction of LP into the reverse micellar phase was studied. The Tween® series surfactants with Aerosol‐OT (bis‐(2‐ethylhexyl) sulfosuccinate) showed better extraction of LP in the reverse micelles (RM) compared to the Triton® and Span® series of surfactants. Complete extraction of LP from an aqueous phase of initial concentration 25 mg L−1 occurred with the RM formed by 90 mM Aerosol‐OT/8 mM Tween® 80 in isooctane. The optimal pH, ionic strength, and positively charged ionic surfactant concentration for back extraction were also studied and a maximum of 95.5% back extraction efficiency and 66% LP activity recovery was obtained for a pH of 10.5,1 M KCl and 60 mM cetyltrimethylammonium bromide system.

Interaction of sodium alginate with cetyltrimethylammonium bromide in aqua-organic mixed solvents: influence of temperatures and compositions

Herein, the interaction of sodium alginate (SA) with cetyltrimethylammonium bromide (CTAB) has been studied in aqueous solution as well as in aqua-organic mixed solvents at varying temperatures using conductivity measurements. Ethylene glycol (EG), dimethyl formamide (DMF), 1,4-dioxane (DO), and acetonitrile (AN) were used as organic solvents. The CMC values for SA + CTAB system in 10% (v/v) mixed solvents follow the order: CMCwater + DO > CMCwater + DMF > CMCwater + AN > CMC water + EG > CMCwater. The CMC values for the SA + CTAB system in aqueous medium indicate that SA lowers the CMC of pure CTAB. The higher CMC values in all the solvent mixtures may be due to the decrease of the dielectric constant and cohesive energy density of water. The interaction of SA with CTAB is affected significantly by the change in temperature which is attributed to changes in hydration of SA and CTAB. The negative values of free energy of micellization () for the SA + CTAB system imply the spontaneous aggregation phenomenon and the negative values in H2O and 10% (v/v) mixed solvents follow the trend: (H2O) > (water + EG) > (water + DMF) > (water + DO) > (water + AN). The values of free energy changes of transfer () were also evaluated for the shift of SA + CTAB mixture from water to aqua-organic mixed solvents and discussed the results in detail. The binding interactions of SA with CTAB are proposed to be hydrogen bonding, ion-dipole, and hydrophobic interactions. The enthalpy-entropy compensation of SA + CTAB systems was assessed and illustrated in detail.

Hybrid molecular/mineral lyotropic liquid crystal system of CTAB and graphene oxide in water

Amphiphilic molecules such as cetyl trimethylammonium bromide (CTAB) and minerals such as graphene oxide (GO) self-assemble to form lyotropic liquid crystal (LLC) systems in water. Here we describe the preparation, structures and mechanical properties of the hybrid CTAB and GO LLC system. We present a series of phase diagrams for the CTAB/GO/water ternary system with independently varying CTAB and GO loadings, covering various combinations of the isotropic and the different lyotropic phases of each that occur as a function of concentration and temperature. The corresponding LLC microstructures are identified through polarised optical microscopy (POM) in a confined environment. We find that GO either promotes or suppresses the formation of the different LLC phases of CTAB depending on the concentration of GO and whether the GO itself is in its isotropic or lyotropic phase, resulting in the formation of a complex hybrid system. GO also significantly depresses the melting point of CTAB at moderate loadings, but the melting point recovers for higher GO loading. Rheology of the CTAB/GO/water system reveals a reinforcement effect of the GO sheets through the formation of CTAB/GO complexes that alter the hexagonal phase nanostructure. Our work reveals the diverse effects on molecular LC phases by an interpenetrating mineral LC phase, and the potential to design a wide range of novel nanostructured hybrid LLC materials.

Distinctive spectroscopic properties and adsorption behaviors of p-sulfonatocalixarene-cetyltrimethylammonium bromide supra-amphiphilic systems

So far, the knowledge about the properties of the calixarene-based supra-amphiphiles remain very limited. In the present study, we investigated the properties of p-sulfonatocalix[n]arene (SC[n], n = 4, 6 and 8)-cetyltrimethylammonium bromide (CTAB) supra-amphiphiles by measuring their fluorescence, UV–vis absorption, 1H NMR spectra as well as surface tension, and found that the calixarene/surfactant mixed systems exhibited special spectroscopic properties and adsorption behaviors. Although SC[n] and CTAB were both non-fluorescent, the resulting SC[n]-CTAB complexes emitted fluorescence; the strongest fluorescence intensity was observed when the molar ratio of CTAB to SC[n] reached the stoichiometry. The SC[n]-CTAB complexes and/or CTAB monomers did not adsorb at the air/water surface until the CTAB content was higher than the stoichiometry. Once CTAB began to adsorb at the surface, the surface tension decreased sharply (much faster than in the absence of SC[n]). Among SC[4], SC[6] and SC[8], SC[4] not only induced the CTAB molecules to line up most tightly at the air/water surface, but also possessed the strongest ability to promote the aggregation of the CTAB molecules in solution. Moreover, proteins did not break the binding between SC[n] and CTAB; they interacted with the complex instead and their activities were closely related to the molar ratio of CTAB to SC[n]. The present study should suggest the potential application of SC[n]/CTAB systems in fields such as fluorescent inks, encryption coding, and regulation of protein activity.

Influence of Additives and Temperature on the Interaction of Acid Red 151 Dye with Cetyltrimethylammonium Bromide: A Conductometric Study

AbstractThe interaction of an anionic textile dye, acid red 151 (AR), with a cationic surfactant, cetyltrimethylammonium bromide (CTAB), in aqueous electrolyte medium (e.g., KCl, NaCl) and in H2O + ethanol medium was observed using the conductometric method. Two critical micelle concentrations (CMC) were found for the AR + CTAB system in water and H2O + ethanol medium, but only one CMC was detected for AR + CTAB in salt+H2O media and for pure CTAB in all solutions. The change in CMC behavior of CTAB in the presence of AR indicates the occurrence of strong interaction between AR and CTAB. The extent of solubility increases with an increase of temperature, which disfavors micellization. The CMC values in NaCl solution are comparatively lower than those found in KCl solution, which signifies that the micelle formation is more favorable in attendance of NaCl. In aqueous ethanol solution, two CMC values were also observed for AR + CTAB that are higher than those obtained in water. The free energy of micellization () was negative, which illustrates a thermodynamically spontaneous micellization process. The values of enthalpy () and entropy () of micellization show that the process was entirely entropically driven at a lower temperature; but, enthalpic events are favored at elevated temperature in electrolyte medium, whereas both enthalpy and entropy are reduced in attendance of ethanol. In aqueous medium, the thermodynamic parameters signify the presence of electrostatic interaction between AR and CTAB at higher temperatures, while the hydrophobic interaction is the main driving force at a lower temperature. A linear expression of as a function of demonstrates enthalpy‐entropy compensation over the experimental conditions employed in this study.

The application of cationic-nonionic mixed micellar media for enhanced solubilization of Direct Brown 2 dye

The present study reports the enhanced solubilizing power of mixed micellar media in comparison to single micellar media. The solubilization of anionic direct dye, Direct Brown 2 (DB-2) has been investigated in micellar media of cationic surfactants; cetyltrimethyl ammonium bromide (CTAB), cetylpyridinium chloride (CPC) and in mixed micellar media of each with nonionic surfactant Triton X-100 (TX-100) using UV–visible spectroscopy and conductometry. The UV–visible spectroscopy has been used to evaluate the degree of solubilization in terms of binding constant, Kb, Gibbs energy of binding, ΔGb, partition coefficient, Kx, and Gibbs energy of partition, ΔGp. Furthermore, electrical conductivity data, taken at different temperatures, has been employed to find out critical micelle concentration (CMC) and different thermodynamic parameters like enthalpy, ΔHm, entropy, ΔSm and Gibbs energy of micellization, ΔGm of reported surfactants in presence of dye. Results reveal spontaneous nature solubilization and binding of dye in both micellar and mixed micellar solutions of surfactants. The micellar system of CTAB as well as mixed micellar solutions of CTAB/TX-100 are recommended to be used to achieve higher degree of solubilization.

The morphology control on the preparation of silver nanotriangles

A seed-mediated growth method was commonly applied to prepare one-dimension nanomaterials. However, some associated particles were unavoidable in the formation of target nanoparticles. Herein, we reported a modified method to prepare silver nanotriangles with higher uniform shape and particle size. The size and morphology of the formed nanoparticles could be controlled by regulating reaction conditions. The results showed that cetyl trimethyl ammonium bromide (CTAB) concentration and seed concentration were related with both the morphology and the particle size. The NaOH concentration, AgNO3 concentration, and the mole ratio of Vc/Ag+ mainly affected the particle size of the formed nanotriangles. The formation of silver nanotriangles may be due to the selective stacking of the new tiny nanoparticles and the oriented growth of silver seed crystals. The oxidizing action of Br−/O2 existing in the CTAB system should be responsible for the final morphology of truncated triangular silver nanoplates.

Influence of end-group modification on interaction of amphiphilic poly(oxyethylene)-b-poly(oxybutylene) block copolymers with ionic surfactants

Amphiphilic poly(oxyethylene)-b-poly(oxybutylene) block copolymers having hydrophilic block end-capped with neutral dimethylamino (DE79B34) and cationic trimethyl ammonium (TE79B34) groups, respectively were investigated for their interactions with ionic surfactants, sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) using tensiometry, conductometry and dynamic light scattering. The self-assembly of DE79B34 and TE79B34 occur at 0.7 g/dm3 and 0.8 g/dm3, respectively. TE79B34 binds favorably with oppositely charged SDS, causing a substantial change in surface tension compared to other surfactant-polymer systems. In mixed polymer-surfactant systems, the micellization was promoted in the presence of SDS, but it was suppressed with CTAB. Such behavior is expected for cationic block copolymers, since they can engage into ion-pair formation with anionic SDS. For neutral polymers, the behavior is reflective of surfactants’ head group hydrophobicity. The head groups of CTAB are more hydrophobic and their existence in the proximity of hydrophobic segments of polymers induces shape transition to non-spherical morphologies. Gibb’s free energy of adsorption at air – water interface is negative for SDS, CTAB and surfactant-block copolymer systems, indicating that the process is highly spontaneous. The increase in entropy of TE79B34 during micelle formation with temperature is due to disturbance of hydrophobic structure of water molecules, thus hydrophobic parts are removed from bulk solution to the interface and also in the interior of micelle the freedom of hydrophobic part is increased. The dynamic laser light scattering results revealed that due to presence of block copolymers pre-micellar aggregates were favored.

Photodecomposition of surfactants using Ti(IV)-doped calcium hydroxyapatite particles

The decomposition of surfactants under UV irradiation was carried out using Ti(IV)-doped calcium hydroxyapatite (TiHap) particles with various Ti/(Ca+Ti) atomic ratios (XTi). The typical cationic, anionic, and nonionic surfactants, namely, cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and polyoxyethylene nonylphenyl ether (NP-15, which has 15 oxyethylene units on average), respectively, were used. CTAB readily decomposed in the presence of TiHap particles with XTi values of 0.10 and 0.20. The plot of CTAB concentration versus time for the decomposition was fitted with a first-order reaction rate equation, and rate constants (k) were obtained. k values for the CTAB system were independent of the XTi values of TiHap particles, that is, TiHap particles facilitated the decomposition of CTAB under UV irradiation. A considerable amount of the hydrocarbon chains in CTAB molecules decomposed because the percentage of CO2 produced (PCP) increased to 55–70% after UV irradiation for 240 h. We also obtained k values for the SDS system using the first-order reaction equation, although the fit was slightly inferior to that observed with the CTAB system. This result may be explained by the electrostatic repulsive force between negatively charged SDS and TiHap particles. In addition, the PCPs after UV irradiation for 120 h slowly increased to 20–35%, which are less than those obtained for CTAB. Nevertheless, few NP-15 molecules (15%) decomposed after UV irradiation for 240 h. The decomposition rates for the three surfactants followed the order CTAB > SDS >> NP-15.

Determination of norfloxacin in food by an enhanced spectrofluorimetric method

Using a norfloxacin (NFLX)-Nd3+ -cetyltrimethylammonium bromide (CTAB) system for the detection of NFLX, a simple and sensitive method based on fluorescence enhancement was developed. In pH 7.0 buffer solution, NFLX reacted with Nd3+ to form a complex, which resulted in fluorescence enhancement of NFLX, and the maximum emission peak shifted from 415 nm for NFLX to 450 nm for NFLX-Nd3+ . Moreover, the fluorescence intensity increased further when the surfactant CTAB was added to NFLX-Nd3+ . Under the optimum conditions, the fluorescence intensity of the NFLX-Nd3+ -CTAB system was linearly correlated with the NFLX concentration in the range 0.038-10 µmol L-1 , with a correlation coefficient (R2 ) of 0.9997. The detection limit (3σ/k) was 0.021 µmol L-1 , indicating that this method can be applied to detect trace NFLX levels. The mechanism of fluorescence enhancement is discussed. The method was used to detect NFLX in fish and chicken samples with satisfactory results. The present results indicate that this method has the potential for fast and real-time determination of NFLX in food samples © 2016 Society of Chemical Industry.

Effect of salts on synthesis of mesoporous materials with mixed cationic and anionic surfactants as templates

Mesoporous silica materials were synthesized using tetraеthoxysilane as precursor and liquid crystals formed in aqueous mixtures of cetyl trimethyl ammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) as templates, without and with the addition of NaBr or Na2SO4. For this purpose, the formation of liquid crystals as a function of the ratio of CTAB and SDS under different conditions was studied. It was found that liquid crystals formed in the mixed system of CTAB and SDS at certain mixing ratios are well-structured templates for the synthesis of mesoporous silicas. The synthesized silica materials were characterized by transmission electron microscope and nitrogen adsorption/desorption analysis. The pore size of mesoporous silicas could be controlled between 3 to 6 nm by simply changing the concentration of NaBr in solution. The mesoporous silicas exhibited lamellar structure and the order of structural arrangement was promoted with addition of NaBr. However, addition of Na2SO4 led to ink-bottle type pores of mesoporous silica with a narrow pore size distribution of around 2 nm and a higher specific surface area of 610 m2 g–1.

Flow-injection chemiluminescence analysis for sensitive determination of atenolol using cadmium sulfide quantum dots

A sensitive, rapid and simple flow-injection chemiluminescence (CL) system based on the light emitted from KMnO4–cadmium sulfide quantum dots (CdS QDs) reaction in the presence of cetyltrimethylammonium bromide (CTAB) in acidic medium was developed as a CL probe for the sensitive determination of atenolol. Optical and structural features of CdS QDs capped with l-cysteine, which synthesized via hydrothermal approach, were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL), and UV–Vis spectroscopy. The CL intensity of KMnO4–CdS QDs–CTAB was remarkably enhanced in the presence of trace level of atenolol. Under optimum experimental conditions, there is a linear relationship between the increase in CL intensity of KMnO4–CdS QDs–CTAB system and atenolol concentration in a range of 0.001 to 4.0mgL−1 and 4.0 to 18.0mgL−1, with a detection limit (3σ) of 0.0010mgL−1. A possible mechanism for KMnO4–CdS QDs–CTAB-atenolol CL reaction is proposed. To prove the practical application of the KMnO4–CdS QDs–CTAB CL method, the method was applied for the determination of atenolol in spiked environmental water samples and commercial pharmaceutical formulation. Furthermore, corona discharge ionization ion mobility spectrometry (CD-IMS) technique was utilized for determination of atenolol.

Fluorescence enhancement effect of Eu(III)–thenoyltrifluoroacetone–cetyltrimethyl ammonium bromide in water-dissolved organic matter extracted from wheat straw

The fluorescence spectral characteristics of water-dissolved organic matter extracted from wheat straw (DOM-WS) were studied using three-dimensional excitation–emission matrix (3D-EEM) fluorescence spectroscopy. The results indicated that 3D-EEM spectra of DOM-WS showed four different fluorophores: humic-like, visible fulvic-like, UV fulvic-like and protein-like substances. It is interesting that DOM-WS can obviously enhance the fluorescence intensity of Eu(III)–thenoyltrifluoroacetone–cetyltrimethyl ammonium bromide system. On the basis of this study, a new fluorescence method for the determination of trace amounts of Eu(III) was developed. Under the optimal conditions, the enhanced fluorescence intensity was in proportion to the concentration of Eu(III) in the range of 8.0×10−8–8.0×10−7mol/L. The detection limit (S/N=3) was 1.1×10−9mol/L. This method was applied to the analysis of Eu(III) concentration in standard sample and obtained satisfactory results. It may be a new way to use wheat straw effectively.

The association effect of quaternary ammonium salt on carboxymethyl cellulose and its analytical applications.

Sodium carboxymethyl cellulose (CMC) has been extensively used in petroleum, geology, common household chemicals, food, medicine and other industries, owing to its excellent water-soluble, emulsifying, water retention and film forming properties. It is known as 'industrial monosodium glutamate'. However, the research of the test method on CMC is far behind the research of its actual application value. This study showed that, weak acid or weak basic medium, the carboxyl groups dissociated from CMC, existing as a big negative ion, which can form ion-association complexes with some quaternary ammonium cations through electrostatic and hydrophobic interactions. The absorption spectrum changes and Triton-X100 can increase the sensitivity of the system. The maximum absorption wavelengths are, respectively, about 256 nm for dodecyl trimethyl ammonium bromide (LTAB), 244 nm for tetradecyltrimethyl ammonium bromide (TTAB) and 240 nm for cetyltrimethyl ammonium bromide (CTAB) with CMC. The reactions show very high sensitivities and the maximum molar absorption coefficients are 1.10 × 10(4) L/(mol·cm) for LTAB system, 1.24 × 10(6) L/(mol·cm) for TTAB system and 1.78 × 10(6) L/(mol·cm) for CTAB system. This method is simple and rapid, and can be applied for the spectrophotometric determination of trace CMC in the supernatant of centrifuged drilling mud.

The change in excited-state proton transfer kinetics of 1-naphthol in micelles upon the binding of polymers: The influence of hyaluronan hydration

The fast deprotonation of 1-naphthol was studied in aqueous solution and in polymer–cetyltrimethylammonium bromide (CTAB) mixtures using picosecond fluorescence spectroscopy to study the influence of hyaluronan hydration in polymer–surfactant interactions. The aqueous micelle solution showed the expected change of proton transfer rate around the reported critical micelle concentration (∼1mM). The proton transfer rate dependence on CTAB concentration in the hyaluronan–CTAB and polystyrenesulfonate–CTAB systems differed significantly from that in the aqueous micelle solution. The dynamic study of excited state proton transfer (ESPT) revealed the significant influence of hyaluronan hydration in CTAB micelles. When hyaluronan–CTAB aggregates were formed at the CTAB concentration of 0.5mM, a tenfold decrease in the rate of deprotonation was observed when compared to polystyrenesulfonate–CTAB aggregates due to hyaluronan hydration. In 2mM CTAB–hyaluronan aggregates, the rate of deprotonation was found to be almost two times faster than in the 2mM CTAB or polystyrenesulfonate–CTAB system. Furthermore, the study of excited-state proton transfer of 1-naphthol confirmed that hyaluronan hydration layer penetrates into the micelle and changes the emission characteristics of 1-naphthol.