Stability of manganese dioxide by guar gum in the absence or presence of surfactants

Stability of the manganese dioxide (MnO₂) suspensions by non-ionic guar gum (GG) in the absence or presence of the surfactants: anionic sodium dodecyl sulphate (SDS), cationic hexadecyltrimethylammonium bromide (CTAB) and non-ionic Triton X-100 (t-octylphenoxypolyethoxyethanol) and their equimolar mixtures (SDS/TX-100; CTAB/TX-100) was measured using turbidity. The obtained results of the manganese dioxide suspensions stability were discussed together with the adsorption data and with the data concerning the thicknesses of the adsorption layers. In order to gain more information about the structure of the electric double layer surface charge density and the zeta potential measurements were performed. The obtained results show that the addition of guar gum to the MnO₂ suspensions increases MnO₂ stability. The larger this increase is, the higher is the concentration of the polymer (concentration range 10–200 ppm). Moreover, the addition of single surfactants also causes the increase in the effectiveness of stabilizing the manganese dioxide suspensions. The reason for that is formation of multilayer complexes between the polymer and the surfactants. In such a system both the adsorption of polymer and the thickness of polymer adsorption layer increase. The greatest increase in the stability of MnO₂/GG suspensions was provided by the mixture of anionic and non-ionic surfactants due to a strong synergistic effect. Also, mixing the polymer and two surfactants reduces the stability of the suspension.     

Primary electroviscous effect in a moderately concentrated suspension of charged spherical colloidal particles

On the basis of the standard theory of the primary electroviscous effect in a moderately concentrated suspension of charged spherical particles in an electrolyte solution presented by Ruiz-Reina et al. (Ruiz-Reina, E.; Carrique, F.; Rubio-Hernández, F. J.; Gómez-Merino, A. I.; García-Sánchez, P. J. Phys. Chem. B 2003, 107, 9528), which is applicable for the case where overlapping of the electrical double layers of adjacent particles can be neglected, the general expression for the effective viscosity or the primary electroviscous coefficient p of the suspension is derived. This expression is applicable for a suspension of spherical particles of radius a carrying arbitrary zeta potentials zeta at the particle volume fraction phi < or = 0.3 for the case of nonoverlapping double layers, that is, at kappaalpha > 10 (where kappa is the Debye-Hückel parameter). A simple approximate analytic expression for p applicable for particles with large kappaalpha and arbitrary zeta is presented. The obtained viscosity expression is a good approximation for moderately concentrated suspensions of the particle volume fraction phi < or = 0.3, where the relative error is negligible for kappaalpha > or =100 and even at kappaalpha = 50 the maximum error is approximately 20%. It is shown that a maximum of p, which appears when plotted as a function of the particle zeta potential, is due to the relaxation effect as in the case of the electrophoresis problem.     

Triton X-100对血红蛋白/利巴韦林/H2O体系中血红蛋白性质和药物释放的影响

通过紫外光谱、荧光光谱、zeta电位、电导率、高效液相色谱和影像分析等方法研究了Triton X-100对血红蛋白/利巴韦林/H2O体系中血红蛋白性质和药物控制释放的影响. 研究结果表明, 随着Triton X-100浓度的增大, 荧光强度、荧光偏振、zeta电位和蛋白的形貌均发生较大的变化, Triton X-100能使增溶定位在蛋白表面中的利巴韦林逐渐游离出来. 当Triton X-100浓度大于1×10^-5 mol·L-1 时, Triton X-100 与血红蛋白的作用占主导地位, 血红蛋白开始明显变性. 少量Triton X-100能保护蛋白免受药物的影响.     

Effects of Triton X-100 on Properties of Hemoglobin and Controlled Release of Drug in Hemoglobin/Ribavirin/H2O System

Effects of Triton X-100 on the properties of hemoglobin (Hb) and on the controlled release of ribavirin were studied using the methods of UV-Vis spectrum, fluorescence spectrum, zeta potential, conductivity, high-performance liquid chromatographic (HPLC), and image morphology in Hb/ribavirin/H₂O system. With the increase of concentration of Triton X-100 in the system, the intrinsic fluorescence intensity, synchronous fluorescence intensity, fluorescence polarization, zeta potential, and morphology of Hb all changed gradually, and the ribavirin located on the Hb surface was dissociated and released out. When the concentration of Triton X-100 was higher than 1×10⁻⁵ mol·L⁻¹, the stronger interaction of Triton X-100 with Hb was predominant. Hb was unfolded and denaturized. A little Triton X-100 can protect Hb from the effects of ribavirin.     

A general chemiluminescence method for the determination of surfactants based on its quenching effect on the luminol-NaIO4-cyclodextrin reaction

Here we report that all types of surfactant could be simply and sensitively determined, by directly quenching the chemiluminescence (CL) between luminol and NaIO4 in a basic solution containing one polyhydroxyl compound such as cyclodextrin (CD), glucose or glycerol. This specific quenching effect was attributed to the change of the microenvironment of the CL reaction, caused by the addition of various surfactants. Based on this fact, the potential use of this CL reaction was exemplified by the cationic surfactant CTMAB, anionic surfactant SDS and non-ionic surfactant Triton X-100. It was found that the measurable range of CTMAB, SDS and Triton X-100 were 4.0 x 10(-6)-4.0 x 10(-4) M by using a basic CD-luminol-NaIO4 CL reaction. With our simple setup, CTMAB, SDS and Triton X-100 were detectable at a concentration as low as 2 microM. Overall, this new CL reaction is quite promising for the post-column determination of surfactant mixtures.     

Trypsin activity assay in substrate-specific one- and two-dimensional gels: a powerful method to separate and characterize novel proteases in active form in biological samples

To separate and identify the proteases, a substrate-specific, sensitive assay in sodium dodecyl sulfate (SDS)-polyacrylamide gels after two-dimensional (2-D) electrophoresis has been developed. This method allows simultaneous determination of protease cleavage specificity, molecular weight, isoelectric point, and if necessary, amino acid sequencing. After isoelectric focusing in immobilized pH gradient (IPG) strips (pH 6-11) (first dimension), trypsin was electrophoresed in 12% SDS polyacrylamide gels (second dimension) copolymerized with Boc-Gln-Ala-Arg-MCA (4-methyl-coumaryl-7-amide). The gels were washed in cold 2.5% Triton X-100 and water, and incubated in assay buffer (6.3 mM Bicine, 100 mM NaCl). Trypsin cleavage of the peptide-MCA generated fluorescent 7-amino-4-methyl-coumarin. In 1-D gels, as low as 500 pg trypsin could be detected and trypsin band volumes correlated linearly with the amounts of trypsin (R(2) = 0.999). In 2-D gels, the lowest amount of trypsin detected was 1 ng. The linear regression of spot volume and loading amount was still good (R(2) = 0.974). To optimize renaturation conditions, 5x5 min washes with 2.5% Triton X-100 and water, respectively, gave the strongest band volume. For fluorescence development, an assay buffer at pH 9 was the best; incubation at 37 degrees C for 30 min was sufficient. The method has application for identifying novel proteases as it does not rely on antibodies.     

Cell model calculation for electrokinetic phenomena in concentrated suspensions: an Onsager relation between sedimentation potential and electrophoretic mobility

Cell model calculations for the electrophoretic mobility, electrical conductivity and sedimentation potential in concentrated suspensions of colloidal particles with low zeta potentials are reviewed with particular emphasis on an Onsager relation between sedimentation potential and electrophoretic mobility. A general Onsager relation is derived on the basis of the thermodynamics of irreversible processes. This relation, which involves the ratio of the electrical conductivity K* of the suspension to the conductivity Kinfinity in the absence of the particles, reproduces the Onsager relation derived from cell model calculations at low zeta potentials, where K*/Kinfinity becomes (1 - phi)/(1 + phi/2), phi being the particle volume fraction.     

Micellar-enhanced ultrafiltration of cadmium ions with anionic–nonionic surfactants

Micellar-enhanced ultrafiltration (MEUF), a surfactant-based separation process, is promising in removing multivalent metal ions from aqueous solutions. The micellar-enhanced ultrafiltration of cadmium from aqueous solution was studied in systems of anionic surfactant and mixed anionic/nonionic surfactants. The micelle sizes and zeta potentials were investigated by dynamic light scattering measurements. The effects of feed surfactant concentration, cadmium concentration and the molar ratio of nonionic surfactants to sodium dodecyl sulfate (SDS) on the cadmium removal efficiency, the rejection of SDS and nonionic surfactants and the permeate flux were investigated. The rejection efficiencies of cadmium in the MEUF operation were enhanced with higher SDS concentration and moderate Cd concentration. When SDS concentration was fixed at 3 mM, the optimal ranges of the molar ratios of nonionic surfactants to SDS for the removal of cadmium were 0.4–0.7 for Brij 35 and 0.5–0.7 for Triton X-100, respectively. With the addition of nonionic surfactants, the SDS dosage and the SDS concentration in the permeate were reduced efficiently.     

Influences of Triton X-100 micelle on the microstructure of HSA

The effects of Triton X-100 molecule and micelle on the microstructure and properties of HSA are studied by the some methods of UV spectrum, fluorescence spectrum, fluorescence polarization, circular dichroism, conductivity, and zeta potential. With the increase of Triton X-100 concentration, the UV absorbance, fluorescence intensity of HSA, and the system conductivity all first decrease and then increase. The zeta potential of HSA first goes up and then down. The percents of the β-sheet, random, turn structures, and the polarization of HSA increase but the percent of the α-Helix of HSA decreases. When Triton X-100 concentration is more than 1.0×10⁻³ mol l⁻¹, the structure parameters change obviously especially for the percents of random and turn structures.     

Comparison of the utility of several tensammetric techniques for the determination of traces of surfactants after preconcentration at the hanging mercury drop electrode

After preconcentration of surfactants at the HMDE, four tensammetric signals were examined to establish the optimum conditions for the determination of ultratraces of surfactants in alkaline, neutral and acidic media. The signals studied were: (1) the depth of the depression occuring on the curves obtained in a.c. fundamental tensammetry; and (2–4) the height of the peaks on the curves obtained in a.c. fundamental tensammetry, a.c. second-harmonic tensammetry and differential pulse tensammetry, respectively. The lowest detection limits found for Triton X-100 and a polyethylene glycol (PEG-4000) were 10 and 2 μg dm^-3, respectively. Traces of surfactants found in supporting electrolytes (ca. 25 μg dm^-3) gave desorption peaks at potentials around ?1 V. These contaminants had no significant effect on the peaks on Triton X-100 and PEG-4000 and they affected the SDS peak markedly. The reproducibility of the results obtained for SDS was poorer than for Triton or PEG.     

Tensammetry with accumulation on the hanging mercury drop electrode : Part 3. The behaviour of triton X-100 in mixtures with PEG-9000

The behaviour of Triton X-100, which can be present in monomeric or associated form, and its mixtures with PEG-9000, which does not undergo association, is described. The tensammetric curve of Triton X-100 alone shows one or two peaks at negative potentials, depending on the concentration of Triton X-100, i.e., on the presence of associated forms. For <2 mg l^?1, there is one broad peak, related to monomers of Triton X-100. The calibration plot for this peak is sigmoidal but its rising section (0.05–0.20 mg l^?1) is approximately linear. The calibration curve of the second, much narrower, peak related to associated forms of Triton X-100, grows parabolically with increasing concentration of Triton X-100. The behaviour of a mixture of PEG-9000 with a larger amount of Triton X-100 is similar to the behaviour of a model mixture of components with sufficiently different properties (e.g., PEG 1500/PEG 9000). The peak for PEG-9000, the stronger surfactant, is relatively less affected by a large amount of Triton X-100. Even this effect can be decreased by using a suitable preconcentration potential (?1.45 V vs. SCE) so that PEG-9000 can be determined in the presence of a 1000-fold amount of Triton X-100. Both peaks of Triton X-100 are greatly decreased by the presence of PEG-9000 and the broad peak can be completely suppressed. Triton X-100 cannot be determined accurately in the presence of unknown amounts of PEG-9000.     

Aqueous dispersion behavior of drug particles by addition of surfactant and polymer

The effect of surfactant and polymer on dispersion stability of aqueous suspensions of 5-(3-ethoxy-4-pentyloxyphenyl)-2,4-thiazolidinedione (CT112) was investigated by measuring the adsorbed amount of surfactant and polymer, zeta potential, particle size, and sedimentation rate of CT112. The addition of celluloses rather than sodium dodecyl sulfate (SDS) provided a high stable suspension of CT112. In addition, mixed systems of celluloses and SDS enhanced CT112 dispersion more effectively. The mechanism of dispersion stability of CT112 by addition of SDS and celluloses is discussed.     

TIME-RESOLVED SPECTROSCOPIC STUDIES ON PHOTOPHYSICAL PROPERTIES OF BENOXAPROFEN IN MICELLAR SOLUTIONS: AN INTRAMICELLAR FLUORESCENCE QUENCHING

The micellar dependencies of the photophysical properties of benoxaprofen (BXP), a 2-phenyl benzoxazole derivative, have been investigated using fluorescence spectroscopy and laser flash photolysis techniques. The fluorescence of BXP in aqueous solution has been observed to be remarkably quenched upon addition of a surfactant, cetyltrimethyl ammonium bromide (CTAB) or Triton X-100, in contrast to its enhancement in sodium dodecyl sulfate (SDS) micellar solution. Time-resolved fluorescence measurements show that the fluorescence decays biexponentially in the micellar solution, indicating the relaxation of micellar environments surrounding the excited BXP. The major component of fluorescence lifetimes in CTAB or Triton X-100 micellar phase is even shorter (330–427ps) than in SDS micellar phase (731 ps). The nonradiative decay constants are significantly larger (ca 3.0 times 10⁹ s^?1) in the CTAB or Triton X-100 micellar phase than in SDS micelles by a factor of ca 10. The major nonradiative decay is interpreted to be the internal conversion due to nuclear geometric change of BXP in the first excited singlet state. This is consistent with the observation that the quantum yields of intersystem crossing are very low (less than 0.01) in the micellar solutions as determined by the laser flash photolysis technique. The laser-induced transient absorption spectrum of BXP in CTAB or Triton X-100 micellar solution shows that the decay kinetics of the transients in CTAB or Triton X-100 are significantly different from first order kinetics in SDS.     

非离子表面活性剂对多壁碳纳米管在乙醇中高浓度分散的作用

如果能在无需聚合物或共价官能团辅助的条件下, 将多壁碳纳米管(MWNTs)高浓度地分散在乙醇中, 那么向各种复合材料引入MWNTs的过程就会更加便捷. 为此, 制备了多种含有表面活性剂的多壁碳纳米管乙醇悬浮液并对比考查了它们的稳定性. 非离子表面活性剂Triton X-100 和Tween 65显示出了在乙醇中分散悬浮高浓度MWNTs的能力, 能够使1.0 g·L-1 MWNTs乙醇悬浮液的上层清液经240 h后浓度仍分别在0.50和0.35 g·L-1以上. 这样长时间稳定的、没有聚合物或共价官能团辅助的MWNTs乙醇悬浮液, 其浓度比文献报道的值高. 进一步探讨了这些非离子表面活性剂分子结构对于分散MWNTs的优势, 并直观给出了其吸附于碳纳米管表面的可能形式. X射线光电子能谱和透射电子显微镜的表征结果都证实了表面活性剂分子吸附于碳纳米管表面.     

Kinetics and mechanism of flocculation of bentonite and kaolin suspensions with polyelectrolytes and the strength of floccs

The effects of cationic (Zetag 7589, Zetag 8660, and SNF 528) and anionic (Magnafloc 1011) polyelectrolytes, as well as the regimes and intensity of suspension stirring, on the kinetics of formation, disruption, and subsequent regrowth of aggregates of bentonite and kaolin particles, are studied in a flow system. The optimum polymer doses and the stirring conditions providing the formation of largest and strongest floccules are found. Under comparable conditions, the effect of the adsorption of the above polymers on the electrokinetic potential and the degree of aggregation of particles is studied. It is shown that intense flocculation takes place long before the isoelectric point of particles is reached. This allows one to conclude that the formation of polymer bridges plays a significant role in the flocculation of the examined suspensions with polyelectrolytes. Different dependencies of flocculation on the dose of added polyelectrolytes have been found for diluted and concentrated suspensions. This is explained by different extents to which flocculants adsorbed on the particle surface approach the equilibrium state at different concentrations of dispersed phases.     

Complexation of serum albumins and triton X-100: Quenching of tryptophan fluorescence and analysis of the rotational diffusion of complexes

The polarized and nonpolarized fluorescence of bovine serum albumin and human serum albumin in Triton X-100 solutions is studied at different pH values. Analysis of the constants of fluorescence quenching for BSA and HSA after adding Triton X-100 and the hydrodynamic radii of BSA/HSA–detergent complexes show that the most effective complexation between both serum albumins and Triton X-100 occurs at pH 5.0, which lies near the isoelectric points of the proteins. Complexation between albumin and Triton X-100 affects the fluorescence of the Trp-214 residing in the hydrophobic pockets of both BSA and HSA.     

Electrical Conductivity of a Concentrated Suspension of Spherical Colloidal Particles

A general expression for the electrical conductivity of a concentrated suspension of spherical colloidal particles is obtained for the case where the particle zeta potential is low and the overlapping of the electrical double layers of adjacent particles is negligible by using Kuwabara's cell model. It is shown how the conductivity of a concentrated suspension depends on the particle volume fraction, the zeta potential zeta, and the reduced particle radius kappaa (kappa = Debye-Hückel parameter and a = particle radius). It is also found that the obtained conductivity formula tends to Maxwell's formula for two different extreme cases: (i) when the particles are uncharged (zeta = 0) and (ii) when the electrical double layers around the particles are infinitesimally thin (kappaa --> infinity). That is, in the latter limiting case (kappaa --> infinity), the conductivity becomes independent of the zeta potential, just as in the case of dilute suspensions. Copyright 1999 Academic Press.     

Change of zeta potential of biocompatible colloidal oxide particles upon adsorption of bovine serum albumin and lysozyme

The amounts of negatively charged bovine serum albumin and positively charged lysozyme adsorbed on alumina, silica, titania, and zirconia particles (diameters 73 to 271 nm) in aqueous suspensions are measured. The adsorbed proteins change the zeta potentials and the isoelectric points (IEP) of the oxide particles. The added to adsorbed protein ratios at pH 7.5 are compared with the protein treated particle zeta potentials. It is found that the amounts of adsorbed proteins on the alumina, silica, and titania (but not on the zirconia) particle surfaces are highly correlated with the zeta potential. For the slightly less hydrophilic zirconia particles high amounts of protein adsorption are observed even under repulsive electrostatic conditions. One reason could be that the hydrophobic effect plays a more important role for zirconia than electrostatic interaction.     

Influence of phosphonium-based ionic liquid on the micellization behavior of surfactants system and potential application in paracetamol drug aggregation

The current study examines the effects of a phosphonium-based ionic liquid, trihexyltetra-decylphosphonium bis-(2,4,4-trimethyl pentyl)phosphinate [THTDPP], on the micellization properties of surfactants, namely sodium dodecyl sulfate (SDS) and Triton X-100 by using the stalagmometry, viscosity, colorimetric, and FTIR methods. The surface adsorption parameters, such as CMC, γ_CMC, Γ_max, A_min, π_CMC, and _pC₂₀, were determined using the stalagmometry method. The results show that with the addition of different weight percentages of [THTDPP], the CMC and γ_CMC values decreased considerably in the following order: water >0.5 wt% of IL > 0.7 wt% of IL > 1.0 wt% of IL. The A_min values decreased with an increase in the wt% of IL for Triton X-100, but for SDS, this value increased. The _pC₂₀ was observed to be greater in Triton X-100 compared to SDS. The ability of [THTDPP] to decrease the CMC was found to be greater in Triton X-100 compared to SDS. The relative viscosity was calculated, and the first observation was made at the pre-CMC stage, where the concentration of SDS+0.7 wt% IL was 4.0 mM. The second finding was made post-CMC at a concentration of 5.0 mM. Afterward, the relative viscosity graph grew slowly and gradually. The functional groups involved in the complexation between [THTDPP] and both surfactants were examined using FTIR spectroscopy. Additionally, the micellar solutions of surfactants + [THTDPP] were used to explore Paracetamol [PCM] aggregation. The findings from UV–vis spectroscopy show that Triton X-100 exhibits the highest binding affinity and has the most encouraging effect compared to SDS.     

Modification of human erythrocyte membrane potentials by the action of the polyoxyethylene detergent Triton X-100

Triton X-100 in sublytic concentrations causes a marked increase in human erythrocyte membrane permeability to cations with small selectivity to K⁺ ions. This membrane permeabilization induces modification of membrane potential: hyperpolarization in low K⁺ media and depolarization in high K⁺ media. Since the specificity of the K⁺-ionophorous action of Triton X-100 is very low in comparison with valinomycin, the membrane potential changes are only in the range of −9 to +5 mV. It is suggested that they are determined by the generation of a diffusion potential across the membrane, although the influence of Triton X-100 on the potentials at cell surfaces cannot be neglected.