Ionic Micelles Research Articles

Microscopic insights on the structural and dynamical aspects of Imidazolium-based surface active ionic liquid micelles

Ionic liquids have drawn vast attention due to their extraordinary physicochemical properties and their relevance in a wide range of applications. As a result of their inherent amphiphilic nature, many ionic liquids are emerging as novel surfactants, being referred to as surface active ionic liquids (SAILs). Under suitable conditions in aqueous solution, these SAILs self-assemble to form nanostructures such as micelles and vesicles. Here, we report on the structure and dynamics of one such SAIL micellar system, 1-Decyl-3-methylimidazolium Bromide (DMIMBr), as studied using fully atomistic molecular dynamics (MD) simulation and quasi-elastic neutron scattering (QENS). Results are compared with a conventional surfactant, dodecyltrimethylammonium bromide (DTAB) micelles. MD simulations showed that while the structure of the DMIMBr micelle is very similar to that of DTAB, the conformational flexibility of the alkyl chains is starkly different. The alkyl chains in the SAIL are more ordered, having fewer gauche defects. This is consistent with experimental results obtained using QENS which also showed slower alkyl chain segmental dynamics. MD results also show restricted dynamics of the hydration water in DMIMBr micelles, of a sub-diffusive nature, suggesting stronger affinity of water molecules to the imidazolium moiety. Thus the decreased flexibility in the alkyl chains could arise from the slower hydration dynamics. In contrast, the lateral motion of the surfactant is found to be relatively faster in DMIMBr micelles than in DTAB micelles. The understanding gained from this study provides a microscopic insight about the dynamical aspects of SAIL micelles, which might be useful for related applications including micellar catalysis and nanoparticle synthesis.

Micellization Behaviour of Cationic Surfactants in the Presence of Food Additives: Conductance and Spectroscopic Investigations

Aim: The micellization behavior of cationic surfactants has been studied in the presence of food additives. Objectives: Micellization behaviour of cationic surfactants, Cetyltrimethylammonium Bromide (CTAB) and Tetradecyltrimethylammonium Bromide (TTAB) has been studied in water and in various concentrations of salts (food additives) L-glutamic acid, sodium propionate, sodium citrate tribasic dihydrate and disodium tartrate dihydrate at (298.15, 308.15 and 318.15) K. Methods: Two methods used in the present study are specific conductance measurements and spectroscopy (NMR) studies. Results: From the specific conductance(κ), various parameters such as Critical Micelle Concentration (CMC), degree of ionization of micelle (α), standard Gibbs free energy (ΔG°m), enthalpy (ΔH°m), and entropy (ΔS°m) of micellization have also been calculated. Thermodynamic parameters related to the micellization process were also analyzed through NMR studies. Conclusion: The CMC values are influenced by the presence of food additive. The magnitude of CMC values increases with an increase in the concentration of food additive. In all the cases, enthalpy of micellization, ΔH°m values are found to be negative, whereas entropy of micellization, ΔS°m values are positive, which indicates that hydrophobic interactions play a major role in the micellization process. Moreover, NMR studies reveal that tartrate and citrate are more hydrated than glutamic acid and propionate, resulting in a more downfield shift.

Novel ionic reverse mixed micelle supramolecules in dispersive liquid-liquid microextraction for the successive/individual sensitive speciation analysis of iron in natural water by UV–Vis spectrophotometry

A sensitive UV–Vis spectrophotometry based procedure is delineated for ultra-trace speciation analysis of iron in natural waters. This study prepares and utilizes new ionic reverse mixed-micelles (i-RMMs) supramolecules for the coacervate microextraction of iron species successively or independently on field. The anionic dioctylsulfosuccinate-capric acid (DOSS-CA) and cationic Aliquat-336-capric acid (Aliquat-336-CA) RMMs are used as dispersing, ion-pairing and extractant, respectively for Fe(II) and Fe(III). In successive speciation, Fe(II) forms colourless Fe(II)-(phen)32+ at ng mL−1 level in weak acidic medium that reacts with anionic head groups of RMM and configurates as Fe(II)-(phen)32+-(DOSS-CA)2 ion-pair in inner hydrophilic core. This coloured ion-pair settles on the top as coacervate and leaves unreacted Fe(III) in bulk aqueous solution, which is extracted in the similar way as Fe(III)-(SCN)63−-(Aliquat-336-CA)3 ion-pair in strong acidic medium. The above strategy can be applied individually to Fe(III)/Fe(II). The iron species stabilized in coacervates are transported to laboratory for UV–Vis spectrophotometry detection. The pre-concentration and detection limits are 16 and 28; and 0.1 and 0.4 ng mL−1, respectively for Fe(II) and Fe(III). The recoveries are between 92 and 100% for both Fe(II) and Fe(III) at 100 ng mL−1. The accuracy is established by correlating the summation of discrete species concentration obtained with certified total iron of NIST CRMs 1643e and 1643f trace elements in water. This field oriented speciation is applied to real natural waters.

Equilibrium Constant, Concentrations Study of <i>p-</i>Aminobenzoic Acid in Anionic, Cationic and Non-ionic Surfactants

p-aminobenzoic acid (pABA) was used as a probe to study the equilibrium constant in ground and excited state and concentrations of anionic surfactant, cationic surfactant and non-ionic surfactant. The absorption and fluorescence spectral characteristics of pABA were reported in aqueous micellar environments (SDS, CTAB and TW 80) at different pHs. The neutral and monoanion form of pABA is present at both pHs 3 and 7 respectively. The blue shifted fluorescence maximum was accompanied by a great raise in intensity at pH 3 whereas at pH 7 the emission intensity a little increase with increasing micelles concentration. In the acidic medium, the CMC value is increased when compared to neutral solution. The strength of interaction between pABA-micelles at both pHs was estimated using Hirose - Sepulveda equation and these calculated values was further used to estimate the free energy change of the interaction from the fluorescence data. These results from the absorption and fluorescence spectra of pABA well explained that the nature of force and location of probe in ionic micelles and non-ionic micelles at different pHs.

Chemical equilibria of Eosin Y and its synthetic ester derivatives in non-ionic and ionic micellar environments

Eosin (EOS) and its synthetic ester derivatives have adequate properties to be employed as histological markers for and as drugs for photodynamic therapy. However, they present a very complex protolytic and tautomeric equilibrium that reflects on their photophysical properties. Hence their biomedical applications are strongly affected by the medium's pH, charge and hydrophobicity. In this study, we evaluated the effects of two neutral (Pluronic® F-127 and P-123) and two ionic (anionic SDS and cationic CTAB) surfactant micelles as a simple membrane model on the protolytic/tautomeric equilibrium of EOS and its ester derivative dyes. Multivariate analysis based on Q-Imbrie's factor and the K-matrix method on the electronic absorption spectroscopy data in different pH conditions allowed for the understanding of the complex protolytic/tautomeric equilibrium, and the influence of medium microenvironment on the EOS dyes at each pH. Our results demonstrated that, when close to physiological pH (~7.4), and electrostatic attraction towards cationic surfaces favor dyes locating close to the micelle's (biomembrane model) interface, where their biomedical applications are favored. Therefore, the analysis in different environments shows that the interactions of EOS and its derivatives with biomembranes can be modulated based on the hydrophobicity of the xanthene derivative and the cell membrane charge.

What happens when pesticides are solubilised in binary ionic/zwitterionic-nonionic mixed micelles?

HypothesisSurfactants have been widely used as adjuvants in agri-sprays to enhance the solubility of pesticides in foliar spray deposits and their mobility through leaf cuticles. Previously, we have characterised pesticide solubilisation in nonionic surfactant micelles, but what happens when pesticides become solubilised in anionic, cationic and zwitterionic and their mixtures with nonionic surfactants remain poorly characterised. ExperimentsTo facilitate characterisations by SANS and NMR, we used nonionic surfactant hexaethylene glycol monododecyl ether (C12E6), anionic sodium dodecylsulphate (SDS), cationic dodecyltrimethylammonium bromide (DTAB) and zwitterionic dodecylphosphocholine (C12PC) as model adjuvant systems to solubilise 3 pesticides, Cyprodinil (CP), Azoxystrobin (AZ) and Difenoconazole (DF), representing different structural features. The investigation focused on the influence of solubilisates in driving changes to the micellar nanostructures in the absence or presence of electrolytes. NMR and NOESY were applied to investigate the solubility and location of each pesticide in the micelles. SANS was used to reveal subtle changes to the micellar structures due to pesticide solubilisation with and without electrolytes. FindingsUnlike nonionic surfactants, the ionic and zwitterionic surfactant micellar structures remain unchanged upon pesticide solubilisation. Electrolytes slightly elongate the ionic surfactant micelles but have no effect on nonionic and zwitterionic surfactants. Pesticide solubilisation could alter the structures of the binary mixtures of ionic/zwitterionic and ionic/nonionic micelles by causing elongation, shell shrinkage and dehydration, with the exact alteration being determined by the molar ratio in the mixture.

A novel non-ionic nanoaggregate sensitized salt induced cloud point extraction of anionic beryllium-chrome azurol S for spectrophotometric determination of beryllium in environmental waters

A simple non-ionic nanoaggregate sensitized and salt induced cloud point extraction (NS-CPE) procedure was reported for the ultra-trace determination of beryllium in environmental waters using spectrophotometer. Chrome azurol S (CAS) and Triton X-114 were used as chelating and extracting agents, respectively. The CAS forms hydrophilic, thermally labile and coloured binary Be-(CAS)24− complex with beryllium. This complex was sensitized by non ionic micelles of Triton X-114, which was further improved by the addition of salt. Moreover, these micellar interactions facilitated room temperature phase separation of coloured Be-(CAS)24− which settled at the bottom of the test tube as a surfactant rich phase. This synergetic process enhanced the binary beryllium complex absorptivity from 1.9 × 104 to 9.2 × 105 L mol−1 cm−1, which is 50 times more compared to direct measurement. This process also avoided the usual blank bias error that occurs with cationic mixed micelles due to the presence of excess of deprotonated CAS used for complexation. The limit of detection and pre-concentration factors were 0.2 ng mL−1 and 10 respectively. At 2–50 ng mL−1 of beryllium, the obtained recoveries were in the range 85–98% with 1–5% relative standard deviation.

The Influence of Ionic Liquids on Micellization of Sodium Dodecyl Sulfate in Aqueous Solutions

The micellization of sodium dodecyl sulfate (SDS) in water and aqueous solutions of NaCl (0.1 M) and three ionic liquids (IL, 0.01 M) with different side-chain length, i.e. 1,3-dimethylimidazolium chloride, 1-ethyl-3-methylimidazolium chloride, and 1-butyl-3-methylimidazolium chloride was investigated in the temperature range from 288.15 to 328.15 K using isothermal titration calorimetry (ITC). Thermodynamics of micellization was studied by the fitting of the mass-action model to the ITC data. The micellization of SDS in all the studied systems is an entropy-driven at lower temperatures and an enthalpy-driven at higher temperatures. It was also found that with the increasing nonpolar character of IL the interactions between the SDS should be stronger leading to more negative Gibbs free energy and enthalpy of micellization. To obtain information about the micellar charge, the conductivity and zeta-potential measurements were performed at 298.15 K. It is assumed that the charge screening between negative sulfate heads is more efficient in the presence of ILs due to their possible incorporation into the micellar structure reflecting in less negative zeta-potential of micelles comparing to SDS in water and consequently higher degrees of micelle ionization due to the larger portion of sodium ions in solution.

Volumetric, acoustic, electrochemical and spectroscopic investigation of norfloxacin–ionic surfactant interactions

Rising levels of bacterial resistance to antibiotics is a persistent and dynamic concern in the field of medicine and demand design and discovery of new and more effective antibiotics. One of the major hurdles in designing new antibiotics which should be capable of passively diffusing across biological membranes is the scarcity of knowledge regarding their biophysical interaction with these membranes. Surfactant systems have been frequently reported in the past decade as potential pseudo-membrane models to understand biophysical interactions of drugs with biological membranes at the molecular level. The present work is aimed at understanding the interaction of norfloxacin (NRF), a fluoroquinolone drug, with dodecyltrimethylammonium bromide (DTAB, a cationic surfactant) and sodium dodecyl sulfate (SDS, an anionic surfactant) at molecular level. Volumetric and acoustic studies of DTAB and SDS in buffered solutions of NRF at physiological pH (7.4) and a temperature range of 298.15 to 313.15 K were performed to calculate apparent molar volume (ɸV), isentropic compressibility (Ks), apparent molar isentropic compressibility (ɸK), partial molar volume (ɸVo), partial molar expansibility (ɸEo), specific acoustic impedance (Z), relative association (RA), intermolecular free length (Lf) and sound velocity number (U). The variation in these quantities as a function of surfactant concentration is interpreted in terms of NRF-ionic surfactant interaction using a cosphere overlap model. Cyclic voltammetry and UV–visible spectroscopy were used to calculate the partition coefficient (Kc) and binding constant (Kb) of NRF with ionic micelles. Free energies calculated from corresponding Kc and Kb values revealed the spontaneity of partitioning and binding of NRF with ionic micelles.

Revealing the Influence of Salts on the Hydration Structure of Ionic SDS Micelles by Contrast-Variation Small-Angle Neutron Scattering.

The influence of lithium chloride (LiCl) on the hydration structure of anionic micelles of sodium dodecyl sulfate (SDS) in water was studied using the contrast-variation small-angle neutron scattering (SANS) technique. In the past, extensive computational studies have shown that the distribution of invasive water plays a critical role in the self-organization of SDS molecules and the stability of the assemblies. However, in past scattering studies the degree of the hydration level was not examined explicitly. Here, a series of contrast-variation SANS data was analyzed to extract the intramicellar radial distributions of invasive water and SDS molecules from the evolving spectral lineshapes caused by the varying isotopic ratios of water. By addressing the intramicellar inhomogeneous distributions of water and SDS molecules, a detailed description of how the counterion association influences the micellization behavior of SDS molecules is provided. The extension of our method can be used to provide an in-depth insight into the micellization phenomenon, which is commonly found in many soft matter systems.

Analytical modeling of micelle growth. 3. Electrostatic free energy of ionic wormlike micelles – Effects of activity coefficients and spatially confined electric double layers

Hypotheses: To correctly predict the aggregation number and size of wormlike micelles from ionic surfactants, the molecular-thermodynamic theory has to calculate the free energy per molecule in the micelle with accuracy better than 0.01 kT, which is a serious challenge. The problem could be solved if the effects of mutual confinement of micelle counterion atmospheres, as well as the effects of counterion binding, surface curvature and ionic interactions in the electric double layer (EDL), are accurately described.Theory: The electric field is calculated using an appropriate cell model, which takes into account the aforementioned effects. Expressions for the activity coefficients have been used, which vary across the EDL and describe the electrostatic, hard sphere, and specific interactions between the ions. New approach for fast numerical calculation of the electrostatic free energy is developed.Findings: The numerical results demonstrate the variation of quantities characterizing the EDL of cylindrical and spherical micelles with the rise of electrolyte concentration. The effect of activity coefficients leads to higher values of the free energy per surfactant molecule in the micelle as compared with the case of neglected ionic interactions. The results are essential for the correct prediction of the size of wormlike micelles from ionic surfactants. This study can be extended to mixed micelles of ionic and nonionic surfactants for interpretation of the observed synergistic effects.

Mechanism on micellization of amino sulfonate amphoteric surfactant in aqueous solutions containing different alcohols and its interfacial adsorption

The process of micellization of amphoteric surfactant sodium 3-(N-dodecyl ethylenediamino)-2-hydroxypropyl sulfonate (C12AS) in aqueous solution without or with alcohols including methanol, ethanol, 1-propanol and 1-butanol and their adsorption behavior at air-liquid interface were investigated with both the tensiometry and the conductometry at 298.15 K. The effect of chain length of alcohol on micellar and interfacial properties were discussed. Some parameters including surface excess concentration (Γmax), minimum area per surfactant molecule (Amin) at air-liquid interface, degree of ionization of micelle, Gordon parameters and cohesive energy density of pure or mixed solvent, and standard free energy of adsorption and micellization, etc. are estimated. At the same amount of alcohol in g/L, the addition of different alcohols changes the values of Γmax, Amin and critical micelle concentration (cmc) of C12AS. Also, the effect of alcohol was discussed. The obtained thermodynamic parameters were used to confirm these behaviors of interfacial adsorption or micellization. These behaviors can be explained theoretically by the change in the polarity or cohesive energy of pure or mixed solvents, the surface charge density of micelle, the partition coefficient of alcohol between micellar pseudophase and intermicellar phase, and the conformation of head group of C12AS on adding alcohol. These findings help with understanding self-assembly behavior of C12AS molecule having electronic delocalization structure at air-liquid interface or in bulk phase and the effect of additives on them, and these results can also provide some information for the design of surfactant formulations and their application in many fields.

Effects of ionic surfactants on the nucleation and growth of cyanidin 3,5-di-O-glucoside capped zerovalent iron nanoparticles

Cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulphate (SDS) were chosen to establish the role of ionic micelles on the morphology of cyanidin 3,5-di-O-glucoside (cyanin) assisted synthesis of zerovalent iron nanoparticles. Nucleation and growth process depends upon the presence of CTAB and SDS. CTAB exhibited catalytic sub-, post- and dilution-micellar effect for the nucleation and growth process of FeNPs formation in the present investigations. Nucleation process of FeNPs formation was inhibited in presence of SDS. The different role of SDS (inhibition) and CTAB (catalysis) micelles might be due to the strong electrostatic attraction and repulsion with Fe3+ ions and cyanin. The reduction rates of Fe3+ ions by cyanin were found to be 3.9 × 10−3, 10.2 × 10−3, and 2.6 × 10−3 s−1 for aqueous, CTAB and SDS, respectively. Transmission electron microscopic images indicate that the FeNPs are roughly spherical and poly dispersed.

Cationic micellar structural growth and their viscoelastic behaviour in mixed surfactants system

ABSTRACT This study discusses the mechanistic details of the cationic micellar transition (growth) in a mixed surfactant system. The aqueous mixed surfactant solution contains cationic micelles at a concentration greater than CMC (critical micelle concentration). These micelles yield a pseudophase of various viscoelastic behaviours. Effects of inert counterionic salts (MX) on the rates of bimolecular reactions (with one of the reactants as reactive counterion) in the presence of ionic micelles may result in either positive or negative catalysis. The kinetics of mixed cationic-noionic micellar-catalysed bimolecular reactions has been used as a probe in the report.

Multivariate analysis of protolytic and tautomeric equilibria of Erythrosine B and its ester derivatives in ionic and non-ionic micelles

Erythrosine B (ERY) is a xanthene dye that has been widely used in recent years as a photoactive drug for Photodynamic Therapy. However, application of ERY and its derivatives as photosensitizer drugs depend not only on their singlet oxygen quantum yield, but also on their hydrophobicity, and photoactive protolytic and tautomeric species. In this work, the objective was to evaluate the acid-base equilibria of ERY and its derivatives: erythrosine methyl ester (ERYMET); erythrosine butyl ester (ERYBUT) and erythrosine decyl ester (ERYDEC), in biomimetic media (micelles of SDS and CTAB) as well as in some drug delivery systems of triblock copolymer Poloxamer (P-123 and F-127). All protolytic chemical equilibria were studied by employing chemometric multivariate analysis based on the Imbrie's Q-Mode Factor Analysis and k-Matrix methods. Tautomeric equilibria were evaluated taking into account of possible chemical structures and electronic spectroscopic approximations. Results from ester derivatives presenting only one protolytic equilibrium (at the phenolate group) and two possible tautomers, allow us to determine that protolytic equilibria follow the sequence pKaCOOH < pKaOH in SDS media for ERY by structure comparison. On the other hand, CTAB and polaxamers inverted the acidity of ERY protolytic groups (pKaOH < pKaCOOH) due to changes in the tautomeric equilibrium due to a lactone formation for the dyes neutral protolytic species inside the micelles. Chemometric approaches provided detailed analyses of protolytic/tautomeric equilibria of ERY. Through this, we achieved a deeper understanding of how ERY and its derivatives are affected by microenvironments in biomimetic and drug delivery systems.

Cloud point-dispersive liquid-liquid microextraction for preconcentration and determination of mercury in wastewater samples by methylsulfanyl thiophenol material

A efficient method based on 4-methylsulfanyl thiophenol (MSTP, C7H8S2) and ionic liquid ([BMIM][PF6]) was used for mercury (Hg) separation and preconcentration from wastewater of petrochemical industries. The 0.01 mile molar of MSTP, 80 mg of [BMIM][PF6] was diluted with 0.2 mL of ethanol (ET 98%). The mixture was injected to 10 mL of wastewater samples, shacked by ultrasonic bath for 5.0 min and cloudy solution was achieved by ionic liquid micelles at pH=7.0. The mercury ions was complexed with MSTP and extracted on micelles (IL/ET) by cloud point dispersive liquid-liquid microextraction (CP-DLLME) at 50oC before determined by cold vapor atomic absorption spectrometry (CV-AAS). The favorite extraction for mercury with low LOD (15 ng L-1) and good linear rages (0.05- 6.2 μg L-1) was achieved (RSD&lt;5%). The main parameters such as, pH, sample volumes, amount of MSTP, amount of IL and ultra-sonic time were optimized.

Design of Experiments-Assisted Development of Clotrimazole-Loaded Ionic Polymeric Micelles Based on Hyaluronic Acid.

Polymeric micelles based on amphiphilic polysaccharides have some advantages as a carrier of poorly soluble lipophilic drugs thanks to their characteristic "core–shell" structure. Previously, ionic polymeric micelles based on chitosan and fatty acids have been developed. The aim of the present study was the preparation and characterization of hyaluronic acid (HA) derivatives by direct ionic interaction between the HA carboxylic groups and the amine groups of dodecyl amine (DDA) and hexadecyl amine (HDA). The HA–HDA polymeric micelles were loaded with a poorly soluble hydrophobic antifungal drug, clotrimazole (CLO). A 23 full factorial experimental design was used to evaluate the effect of the following factors: HA/HDA ratio from 1:0.25 to 1:0.75, cholesterol (CHOL%) as percentage of HA from 10% to 30%, and preparation temperature from 20 to 40 °C. As dependent variables (responses), nanoparticle dimensions and clotrimazole concentration in the final colloidal dispersion were considered. To optimize the drug final concentration, the design was therefore expanded into a rotatable central composite design (CCD). The effects of the formulation variables and the composition of the optimized formulation were confirmed by a mixture design. Physicochemical characterization of the optimized formulation was performed, confirming the ionic interaction between the polysaccharide and the HDA.

Physicochemical and spectral evaluation of the interactional behavior of nicotinic acid (vitamin B3) with mixed [sodium deoxycholate (bile salt) + cetyltrimethylammonium bromide] surfactants

Aggregation behavior of anionic bio-surfactant; sodium deoxycholate (SDC) and cationic surfactant; cetyltrimethylammonium bromide (CTAB) and their mixtures at different mole fractions, αSDC = (0.90026, 0.88416, and 0.69438) has been examined in water as well as in aqueous solutions of nicotinic acid at (298.15, 308.15, and 318.15) K by employing various techniques such as conductivity, density, sound velocity, UV–visible spectroscopy, and dynamic light scattering (DLS) studies. From the critical micelle concentration (CMC) and the degree of ionization (α) of micelle, thermodynamic parameters {standard Gibbs free energy (), enthalpy (), and entropy () of micellization} have been evaluated and analyzed for surfactants studied in water and in (1, 2, and 3) × 10−4 mol kg−1 nicotinic acid(aq) solutions at (298.15, 308.15, and 318.15) K. The CMC values for both the pure and mixed (SDC + CTAB) surfactants were found to increase with increase in concentration of nicotinic acid. The partial specific volume (φv), isentropic compressibility (κs), and partial specific isentropic compressibility (φκ) were estimated from density and speed of sound data. UV–vis absorption spectra of 1 × 10−4 mol kg−1 nicotinic acid(aq) solutions were also recorded in presence of surfactants studied at αSDC = (0.90026, 0.88416, 0.69438) and T = 298.15 K. Hydrodynamic diameters (Dh) of micellar aggregates for both pure and mixed surfactants were analyzed through the DLS studies performed at 298.15 K. The results from all the studies suggest the supremacy of both hydrophobic and electrostatic interactions between the nicotinic acid and the mixed micellar aggregates.

Determination of the Critical Micelle Concentration of Imidazolium Ionic Liquids in Aqueous Hydrogen Peroxide.

The critical micelle concentrations (CMCs) of several imidazolium-based ionic liquids (ILs) in aqueous H2O2 (50 wt % in H2O) were determined by tensiometry, conductometry, and the rate of catalytic epoxidation of cis-cyclooctene. CMC values in aqueous H2O2 were significantly lower compared to values in pure water. In both H2O2 solution and water, the CMC of all ILs decreases with an increasing alkyl chain length and increases with a rising temperature. The degree of micelle ionization of 1-methyl-3-octylimidazolium tetrafluoroborate ([OMIM][BF4]) was calculated by conductometry in a temperature range of 22-70 °C.

Influence of ammonium salts on the interaction of fluoroquinolone antibiotic drug with sodium dodecyl sulfate at different temperatures and compositions

The interaction between sodium dodecyl sulfate (SDS) and an antibiotic drug, ciprofloxacin hydrochloride (CPFH) has been carried out by conductometric measurement at various temperatures from 298.15 K to 318.15 K. The critical micelle concentration (cmc) values of SDS/SDS+CPFH mixture were attained to be reduced in the electrolytes medium. The effect on the cmc reduction is higher in case of ammonium carbonate than ammonium chloride. The cmc values of SDS/SDS+CPFH mixture follow U-shaped behavior with temperature in water and ammonium chloride and reversed U-shaped in ammonium carbonate solution. In the existence of CPFH, the cmc of SDS reduces in aqueous medium but enhances in the electrolytes medium. The extent of micelle ionization (α) was found to be enhanced with the increase of concentration of CPFH in aqueous medium and in ammonium chloride medium at a lower temperature. The α values follow inverted U-shaped in ammonium carbonate medium. The estimated values of ΔGmo for distinct SDS, as well as SDS+CPFH mixtures, were obtained to be negative in entire cases illustrating the spontaneity of micellization. The magnitudes of ΔHmo, ΔSmo and thermodynamic parameters of transfer have been evaluated and discussed in details.