Sodium Octylsulfonate Research Articles

Development and Validation of a New High-Performance Liquid Chromatography-Ultraviolet Assay for Quantification of Mitoxantrone in Plasma of BALB/c-nu Mice.

The concentration of mitoxantrone in the blood of mice was determined by a high-performance liquid chromatography-ultraviolet method with aloe-emodin as the internal standard. The separation was performed on a Hypersil BDS2 column (4.6 × 250mm, 5μm) as the analytical column, the mobile Phase A was acetonitrile, and B was 20-mM potassium dihydrogen phosphate (adding 1% triethylamine and adjusting the pH to 2.8 with phosphoric acid) and 4.6-mM sodium octyl sulfonate. The flow rate was 1.0mL·min-1, the detection wavelength was 243nm, the column temperature is 25 ± 5°C and the injection amount was 20μL. Finally, the linear range of mitoxantrone was 5-200μg·mL-1, and the correlation coefficient was r = 0.9999. The recovery rate of the method was 91.93-105.5%, and the extraction recovery rate was 91.45-105.5%. The intraday precision and interday precision were <3.29% (limit of detection = 0.3μg·mL-1). The HPLC method established in this paper was simple, rapid, sensitive and accurate, and can be used to determine the content of mitoxantrone in mouse plasma after tail vein injection.

The Spontaneous Vesicle-Micelle Transition in a Catanionic Surfactant System: A Chemical Trapping Study.

Typically, the formation of vesicles requires the addition of salts or other additives to surfactant micelles. However, in the case of catanionic surfactants, unilamellar vesicles can spontaneously form upon dilution of the micellar solutions. Our study explores the intriguing spontaneous vesicle-to-micelle transition in catanionic surfactant systems, specifically cetyltrimethyl ammonium bromide (CTAB) and sodium octylsulfonate (SOS). To gain insights into the changes occurring at the interface, we employ a chemical trapping method to characterize variations in the molarities of sulfonate headgroups, water, and bromide ions during the transition. Our findings reveal the formation of ion pairs between the cationic component of CTAB and the anionic component of SOS, leading to tight interfacial packing in CTAB/SOS solutions. This interfacial packing promotes vesicle formation at low surfactant concentrations. Due to the significant difference in critical micelle concentration (cmc) between CTAB and SOS, an increase in the stoichiometric surfactant concentration results in a substantial rise in the SOS-to-CTAB ratio within the interfacial region. This enrichment of SOS in the aggregates triggers the transition from vesicles to micelles. Overall, our study may shed new light on the design of morphologies in catanionic and other surfactant systems.

Interplay between bulk self-assembly, interfacial and foaming properties in a catanionic surfactant mixture of varying composition.

The self-aggregation, surface properties and foamability of the catanionic surfactant mixture cetyltrimethylammonium bromide (CTAB)/sodium octyl sulfonate (SOSo) have been investigated to obtain insight on the relation between bulk nanostructures, surfactant packing, and foam stability and aging. Light microscopy, SANS, cryo-TEM, DLS, surface tension, rheometry and direct photography were used to characterize mixtures with varying CTAB molar fraction, xCTAB. In the bulk, self-assembly is richer in the excess CTAB region than in the excess SOSo one. Starting from neat CTAB micelles and on addition of anionic surfactant, there is a change from small ellipsoidal micelles (1 < xCTAB ≤ 0.80) to large rodlike micelles (0.65 ≤ xCTAB ≤ 0.55) and then to vesicles (0 < xCTAB ≤ 0.50), with coexistence regions in between; SOSo-rich mixtures are thus dominated by vesicles. High size polydispersity for the micelles and vesicles is an intrinsic feature of this system. Foam stability is concomitantly impacted by xCTAB. SOSo is a small mobile molecule and so it disrupts foam stability, irrespective of the presence of vesicles. Foams are thus only stable in the CTAB-rich regions, and SANS shows that the shape of micelles and vesicles is unchanged inside the foam. Foam drainage is thereby mostly controlled by the presence of the elongated micelles through the solution viscosity, whereas coarsening is influenced by dense surfactant packing at the gas-liquid interfaces.

Determination of cinnamic acid by capillary zone electrophoresis using ion-pair reagents

The behavior of cinnamic acid in the presence of ion-pair reagents has been studied. Conditions have been chosen for the selective determination of cinnamic acid by capillary zone electrophoresis with normal and reversed polarity and spectrophotometric detection; the results have been applied for the analysis of drinks and milk hydrolysates. The influence of surfactants (sodium dodecyl sulfate, sodium octyl sulfonate) present in the buffer electrolyte on the efficiency of cinnamic acid determination is discussed.

Micellization behavior of a catanionic surfactant with high solubility mismatch: Composition, temperature, and salt effects

While cationic/anionic surfactant mixtures have been reported to form strongly non-ideal mixed aggregates in aqueous solution, the micellization of true catanionic surfactants, i.e. the salt-free ion-paired compounds obtained from the mixtures, has been much less investigated. However, if there is a significant solubility mismatch between the paired chains, these surfactants may show less conventional aggregation features in water, such as a temperature-driven vesicle–micelle transition and the coexistence of two lamellar phases in equilibrium. In this work, we carry out micellization studies for a catanionic surfactant of the type C 16 +C 8 −, cetyltrimethylammonium octylsulfonate (TASo), by surface tension and conductivity measurements. For comparison purposes, the catanionic mixture cetyltrimethylammonium bromide (CTAB)/sodium octylsulfonate (SOSo) at different mixing ratios and the neat SOSo have also been studied. For the non-ideal CTAB/SOSo mixture, Rubingh's model has been applied to determine the β interaction parameter and the mixed micelle composition. The cmc of TASo has been investigated as a function of temperature, salt and excess ionic surfactant, displaying some differences with respect to conventional ionic and nonionic surfactants. The trends in the thermodynamic parameters of micellization of the three types of systems are comparatively rationalized.

Determination of dopamine, serotonin, and their metabolites in pediatric cerebrospinal fluid by isocratic high performance liquid chromatography coupled with electrochemical detection

A method to rapidly measure dopamine (DA), dihydroxyindolphenylacetic acid, homovanillic acid, serotonin (5-HT) and 5-hydroxyindoleacetic acid concentrations in cerebrospinal fluid (CSF) has not yet been reported. A rapid, sensitive, and specific HPLC method was therefore developed using electrochemical detection. CSF was mixed with an antioxidant solution prior to freezing to prevent neurotransmitter degradation. Separation of the five analytes was obtained on an ESA MD-150 x 3.2 mm column with a flow rate of 0.37 mL/min and an acetonitrile-aqueous (5 : 95, v/v) mobile phase with 75 mM monobasic sodium phosphate buffer, 0.5 mM EDTA, 0.81 mM sodium octylsulfonate and 5% tetrahydrofuran. The optimal electrical potential settings were: guard cell +325 mV, E1 -100 mV and E2 +300 mV. Within-day and between-day precisions were <10% for all analytes and accuracies ranged from 91.0 to 106.7%. DA, 5-HT, and their metabolites were stable in CSF with antioxidant solution at 4 degrees C for 8 h in the autoinjector. This method was used to measure neurotransmitters in CSF obtained from children enrolled on an institutional medulloblastoma treatment protocol.

Determination of the dopamine agonist rotigotine in microdialysates from the rat brain by microbore column liquid chromatography with electrochemical detection

Rotigotine, an investigational dopamine agonist formulated as a patch, is being studied in Parkinson's disease. A microdialysis technique, in combination with microbore column liquid chromatography and electrochemical detection, was developed to monitor rotigotine levels in the brain. Microdialysis probes were inserted into the striata of anesthetized rats, and samples were collected during perfusion with Ringer's solution. Rotigotine was separated using a C18 reversed-phase column. The mobile phase consisted of 50 mM Na 2HPO 4·2H 2O, 2.5 mM sodium octyl sulfonate, and pH 4.5; 35% volume to volume acetonitrile. The flow rate was 30 μl/min, and the potential of the glassy carbon electrode was set to +850 mV. The method allowed monitoring of the time course of brain extracellular rotigotine levels with a detection limit of 1 nM following either intravenous (0.5 mg/kg) or subcutaneous (5.0 mg/kg) rotigotine injection.

Zero Spontaneous Curvature and Its Effects on Lamellar Phase Morphology and Vesicle Size Distributions

Equimolar mixtures of dodecyltrimethylammonium chloride (DTAC) and sodium octyl sulfonate (SOSo) show a vesicle phase at >99 wt % water and a single, fluid lamellar phase for water fractions below 80 wt %. This combination is consistent with the bilayer bending elasticity kappa approximately k(B)T and zero bilayer spontaneous curvature. Caillé line shape analysis of the small-angle X-ray scattering from the lamellar phase shows that the effective kappa depends on the lamellar d spacing consistent with a logarithmic renormalization of kappa, with kappa(o) = (0.8 +/- 0.1)k(B)T. The vesicle size distribution determined by cryogenic transmission electron microscopy is well fit by models with zero spontaneous curvature to give (kappa + (kappa/2)) = (1.7 +/- 0.1)k(B)T, resulting in kappa = (1.8 +/- 0.2)k(B)T. The positive value of kappa and the lack of spontaneous curvature act to eliminate the spherulite defects found in the lamellar gel phases found in other catanionic mixtures. Current theories of spontaneous bilayer curvature require an excess of one or more components on opposite sides of the bilayer; the absence of such an excess at equimolar surfactant ratios explains the zero spontaneous curvature.

Improved HPLC Assay for Measuring Serum Vitamin C with 1-Methyluric Acid Used as an Electrochemically Active Internal Standard

The National Health and Nutrition Examination Survey (NHANES) laboratory at CDC has used a modification of methods (1)(2) with electrochemical detection for measurement of serum vitamin C for the past 9 years. The assay is relatively rapid, easy to perform, and gives good precision. Quality-control (QC) materials have been kept at −70 °C for more than 10 years without substantial degradation. A drawback of the method is the lack of an internal standard to correct for analyte degradation, procedural errors, and detector drift. Significant vitamin C degradation is intermittently encountered during the analytical process. Oxidation of ascorbic acid (AA) is accelerated by exposure to air, heat, light, and traces of copper and iron (3) and may be introduced through contact with unexpected sources, such as consumable supplies (4). Detector drift is a characteristic of electrochemical detection and has been noted by others performing the serum AA assay (5). Our original HPLC assay used partition of largely un-ionized AA and amperometric detection. A 25-cm C18 reversed-phase column is equilibrated with a mobile phase consisting of monochloroacetic acid (pH 3.0) containing disodium EDTA and sodium octylsulfonate [originally used for ion pairing with catecholamines extracted from adrenal chromaffin cells in a mixture containing AA (1)]. The AA in serum is stabilized by addition of metaphosphoric acid (MPA), reduced by addition of dithiothreitol (DTT), and then oxidized at +650 mV referenced to an Ag/AgCl electrode. The working electrode is a thin-layer detector cell. When serum is treated as indicated, peaks for AA, uric acid (URIC), and DTT are resolved and detected at the applied potential within ∼18 min. The run time for each sample is shortened by injecting the next sample before all peaks from the previous sample have eluted. Several changes suggested themselves to modify this method: (a) Improved …

Ionic surfactant–polymer interaction in aqueous solution

The interactions in aqueous solution between poly(vinylpyrrolidone) (PVP) and sodium nonanoate (C8COONa), sodium octylsulfonate (C8SNa), lithium perfluorononanoate (C8FCOOLi), respectively, were investigated. In all the studied systems, the presence of PVP induces a lowering of the aggregation number of the surfactant as evidenced by fluorescence quenching measurements. However, no direct surfactant–polymer interaction has been found for the systems C8COONa–PVP and C8SNa–PVP. Strong hydrophobic interaction in the system C8FCOOLi–PVP has been shown by the fluorescent behavior of pyrene used as a probe. The presence of the fluorinated surfactant induces an increment of ∼14% of the polymer gyration radius, as shown by viscosimetry. Calorimetry confirms the experimental results obtained through fluorescence and shows that the adsorption of C8FCOOLi on PVP is an endothermic process.

On the Presumed Specific Interaction of Anionic Surfactants with Nonionic Polymers. Aqueous Solution of Sodium Alkylsulfonate in the Presence of Poly(vinylpyrrolidone): An “Excluded Volume” Effect

Surface tension, viscosity, intradiffusion, and interdiffusion measurements have been performed on aqueous solutions of sodium octyl sulfonate, sodium decyl sulfonate, and sodium undecyl sulfonate, in the presence of poly(vinylpyrrolidone) at 1% w/w. The experimental measurements for each ternary system were performed in a range of surfactant concentration including the binary critical micelle concentration of the surfactant. The overall picture of the properties studied suggests the absence of a specific interaction between poly(vinylpyrrolidone) and alkylsulfonate surfactants. The experimental diffusion coefficients can be interpreted in terms of an “excluded volume” effect produced by the presence of the polymer in solution.

Langmuir behaviors of the complex of anionic and cationic surfactant at the air/water interface

The complexes of anionic and cationic surfactant were prepared by mixing a cationic surfactant (cetylpyridinium chloride (CPCl, C 16) with anionic surfactant ((sodium octyl sulfonate (OSS, C 8), sodium dodecyl sulfate (SDS, C 12), sodium tetradecyl sulfonate (TDSS, C 14), sodium dodecyl benzene sulfonate (SDBS, C 12)) having different alkyl chain lengths in 0.15 M NaCl aqueous solution. The behaviors of precipitates at the air/water interface were studied by surface-pressure–area isotherm, surface potential and Brewster angle microscopy (BAM), respectively.

The origins of stability of spontaneous vesicles.

Equilibrium unilamellar vesicles are stabilized by one of two distinct mechanisms depending on the value of the bending constant. Helfrich undulations ensure that the interbilayer potential is always repulsive when the bending constant, K, is of order k(B)T. When K k(B)T, unilamellar vesicles are stabilized by the spontaneous curvature that picks out a particular vesicle radius; other radii are disfavored energetically. We present measurements of the bilayer elastic constant and the spontaneous curvature, R(o), for three different systems of equilibrium vesicles by an analysis of the vesicle size distribution determined by cryo-transmission electron microscopy and small-angle neutron scattering. For cetyltrimethylammonium bromide (CTAB)/sodium octyl sulfonate catanionic vesicles, K =.7 k(B)T, suggesting that the unilamellar vesicles are stabilized by Helfrich-undulation repulsions. However, for CTAB and sodium perfluorooctanoate (FC(7)) vesicles, K = 6 k(B)T, suggesting stabilization by the energetic costs of deviations from the spontaneous curvature. Adding electrolyte to the sodium perfluorooctanoate/CTAB vesicles leads to vesicles with two bilayers; the attractive interactions between the bilayers can overcome the cost of small deviations from the spontaneous curvature to form two-layer vesicles, but larger deviations to form three and more layer vesicles are prohibited. Vesicles with a discrete numbers of bilayers at equilibrium are possible only for bilayers with a large bending modulus coupled with a spontaneous curvature.

The origins of stability of spontaneous vesicles

Equilibrium unilamellar vesicles are stabilized by one of two distinct mechanisms depending on the value of the bending constant. Helfrich undulations ensure that the interbilayer potential is always repulsive when the bending constant, K, is of order k(B)T. When K k(B)T, unilamellar vesicles are stabilized by the spontaneous curvature that picks out a particular vesicle radius; other radii are disfavored energetically. We present measurements of the bilayer elastic constant and the spontaneous curvature, R(o), for three different systems of equilibrium vesicles by an analysis of the vesicle size distribution determined by cryo-transmission electron microscopy and small-angle neutron scattering. For cetyltrimethylammonium bromide (CTAB)/sodium octyl sulfonate catanionic vesicles, K =.7 k(B)T, suggesting that the unilamellar vesicles are stabilized by Helfrich-undulation repulsions. However, for CTAB and sodium perfluorooctanoate (FC(7)) vesicles, K = 6 k(B)T, suggesting stabilization by the energetic costs of deviations from the spontaneous curvature. Adding electrolyte to the sodium perfluorooctanoate/CTAB vesicles leads to vesicles with two bilayers; the attractive interactions between the bilayers can overcome the cost of small deviations from the spontaneous curvature to form two-layer vesicles, but larger deviations to form three and more layer vesicles are prohibited. Vesicles with a discrete numbers of bilayers at equilibrium are possible only for bilayers with a large bending modulus coupled with a spontaneous curvature.

Π-A isotherms for anionic, cationic and mixed anionic–cationic surfactants

Adsorption of dodecyltrimethylammonium bromide (DTMABr) and sodium octyl sulfonate (NaOS) from single component solutions and from solutions of their mixtures has been investigated. Π-A isotherms of adsorption at the air/water and the decane/water interfaces are presented. The mean molecular area of surfactants in the monomolecular films is shown, versus the bulk concentration of the particular surfactant. It has been discovered that the adsorption films at the air/water surface are more condensed than at the decane/water interface. The molecular area larger for DTMABr than for NaOS is a result of the additional Van der Waals attractive forces between decane molecules and methyl groups in DTMABr molecule. When mixtures of surfactants are concerned, it has been found that the higher the content of NaOS in the mixture, the more condensed are the adsorption films at the air/water interface.

Volume collapse of a cationic poly(ethyleneimine) gel induced by the binding of anionic surfactants

A cationic polyelectrolyte gel was prepared by the crosslinking of poly(ethylenimine) (PEI; linear type) with ethylene glycol diglycidyl ether. The swelling characteristic of the PEI gel was investigated as a function of pH, kinds of surfactants, and their concentrations. Four different alkyl sulfate and sulfonates were used: sodium octyl sulfonate (SOS), sodium butyl sulfonate (SBS), sodium dodecyl sulfate (SDS), and sodium dodecylbenzen sulfonate (SDBS). The surfactant binding was also studied through the SDBS uptake by the gel at various concentrations and at pH 3. The following features were observed in the swelling experiments: (a) SDBS, SDS and SOS brought about a discontinuous gel collapse (i.e. volume transition), whereas the gel continuously shrunk with SBS, a behavior which is very close to that with NaCl; (b) the concentration leading to the transition was in the order SDBS<SDS<SOS, and shifted to a low concentration range when increasing the temperature; (c) the SDBS binding levelled off when the surfactants bound to about 40% of the total ionizable groups (–NH– or –N) in the gel, but almost three molecules of the surfactant anions bound to one binding site consisting of either –NH 2 +– or –NH + cations. These results suggest an inhomogeneous surfactant binding to the PEI gel, in which the electrostatic interaction between the opposite charges of the surfactant and the gel as well as the hydrophobic interaction due to the bound surfactant molecules seem to play an important role. The staining of the bound surfactant anions with cationic dyes such as Crystal Violet and Toluidene Blue showed that the inhomogeneous surfactant binding occurs mainly in the region in the near vicinity of the gel surface.

Surfactant-mediated gelation of hydrophobically modified hydroxyethyl cellulose: effects of polymer and surfactant structure

We have investigated the effects of polymer structure, surfactant structure, and system composition on the phase behavior of a nonionic hydrophobically modified cellulose ether (HMHEC) and the rheological properties of selected hydrogels. Specific conditions under which strong hydrogels phase separate out of these systems have been identified. Gel formation is favored when the side chain level on the polymer is ∼210 side chains/backbone. In general, gel strength increases with increasing polymer molecular weight but does not scale with side chain content on the polymer. A mechanism for this is proposed. Stronger gels formed in sodium dodecyl sulfate (SDS) than in sodium octyl sulfate (SOS) or sodium octyl sulfonate (SS), suggesting that the surface activity of a surfactant, which is proportional to the length of its tail group and inversely proportional to its critical micelle concentration (cmc), governs the extent of surfactant binding to the polymer as well as the extent of polymer/polymer hydrophobic association.

Properties of anionic–cationic adsorption films

The regular solution model for mixed monolayers was used to calculate the composition of the anionic–cationic adsorption films and parameters characterizing the mutual interactions between their components. The surfactants forming the mixed monolayers were decylpyridinium chloride and sodium hexylsulfonate. The monolayers under investigation were all adsorbed from equimolar solutions of surfactants. The results obtained show that the composition of the anionic–cationic adsorption films is dependent on the concentration and the kind of inorganic electrolyte present in the solution. The values of surface interaction parameter β, being all negative, show that the adsorbed components attract mutually. It has been observed that the strength of the attraction mentioned is also dependent on the factors given above for the composition of mixed adsorption films. It has also been established that the system examined here behaves, both qualitatively and quantitatively, in very similar manner to the previously investigated mixture of decylpyridinium chloride and sodium octylsulfonate, i.e. of surfactants with the same difference in length of the hydrocarbon chains as examined in this work.

Determination of Association Constants for Cyclodextrin–Surfactant Inclusion Complexes: A Numerical Method Based on Surface Tension Measurements

Inclusion complexes of β-cyclodextrin (β-CD) with sodium octyl sulfonate (C8As), sodium dodecyl sulfonate (C12As), and sodium hexadecyl sulfonate (C16As) in aqueous solutions are studied by surface tension measurement at the air/water interface at different temperatures. At fixed concentrations of the surfactants, the surface tension increases with an increase in β-CD concentration to a maximum value, at which it holds. The surface tension curves of the surfactants in the presence of β-CD are higher than those in the absence of β-CD. The curves rise higher with the increase in β-CD concentration for each surfactant. The apparent critical micelle concentrations (CMC*) of the surfactants vary linearly with β-CD concentration. The CMC* and surface tension values (including those after the CMC*) for the same system decrease with increase in temperature. A numerical method based on surface tension measurements is developed to determine the association constants for 1:1 inclusion complexes. This method is very reliable and easy to perform. The results demonstrate that the longer the hydrophobic tail of the surfactant, the greater the association constant with β-CD, and that for the same surfactant the association constant is higher at lower temperatures.

Surface Tension and 1H NMR Studies on Inclusion Complexes of β-Cyclodextrin with Sodium Alkyl Sulfonate

The inclusion complexes of β-CD with sodium octylsulfonate (C8As), sodium dodecyl sulfonate (C12As), andsodium hexadecyl sulfonate (C16As) in aqueous solutions havebeen studied by surface tension measurement at the air/water interfaceand 1H NMR spectroscopy at 323 K.