Home About us Contact
|
Home About us Contact | ||
|
|
||
Organic Additive (organic + additive)
Selected AbstractsMicelle-to-Vesicle Transition Induced by Organic Additives in Catanionic Surfactant SystemsCHEMISTRY - A EUROPEAN JOURNAL, Issue 10 2006Haiqing Yin Abstract A micelle-to-vesicle transition (MVT) induced by the addition of a series of apolar hydrocarbons (n -butylbenzene, n -hexane, n -octane, and n -dodecane) to the catanionic surfactant system n -dodecyltriethylammonium bromide/sodium n -dodecylsulfate (DTEAB/SDS) has been investigated for the first time by means of rheology and turbidity measurements, dynamic light scattering (DLS), and transmission electron microscopy (TEM). Interestingly, a MVT can take place within certain micellar regions, which are dependent on the structure and chain length of the hydrocarbon. However, these hydrocarbons are unable to induce a MVT in another catanionic surfactant system, namely, n -dodecyltriethylammonium bromide/sodium n -dodecylsulfonate (DTEAB/SDSO3), in which the molecular interactions are weaker than in the DTEAB/SDS system. On the other hand, polar additives, such as n -octanol and n -octylamine, exhibit much higher efficiency and activity in inducing MVT than hydrocarbons in both DETAB/SDS and DTEAB/SDSO3. Moreover, DLS, TEM, and time-resolved fluorescence quenching (TRFQ) results demonstrate that the ratio of vesicles to micelles in the system can be actively controlled by addition of polar additives. Possible mechanisms for the above phenomena are presented, and the potential application of controllable micelle/vesicle systems in the synthesis of tailored bimodal mesoporous materials is discussed. [source] Microstructure of microemulsion in MEEKCELECTROPHORESIS, Issue 4 2010Yuhua Cao Abstract The influences of the composition of microemulsion on the microstructure including dimensions and , potentials of microdroplets were measured in details. The average dynamic dimension of microdroplets was measured by dynamic laser light scattering, and , potential was determined to characterize average surface charge density of microdroplets. The experiment results showed that increase of the amount of surfactant resulted in decrease of microdroplet size but almost invariant , potential, which would enlarge migration time of the microdroplet in MEEKC. With increment of cosurfactant concentration, the microdroplet size had an increasing trend, whereas the , potential decreased. Thus, observed migration velocity of microdroplets increased, which made the separation window in MEEKC shortened. Neither dimension nor , potential of microdroplets changed by varying both the type and the amount of the oil phase. Adding organic solvent as modifier to microemulsion did not change the microdroplet size, but lowered , potential. The migration time of microdroplet still became larger, since EOF slowed down owing to organic solvent in capillary. So, besides increment of surfactant concentration, organic additive could also enlarge the separation window. Increase of cosurfactant concentration was beneficial for separation efficiency thanks to the looser structure of swollen microdroplet, and the peak sharpening might compensate for the resolution and peak capacity owing to a narrow separation window. Except the oil phase, tuning the composition of microemulsion would change the microstructure, eventually could be exploited to optimize the resolution and save analysis time in MEEKC. [source] Enantioselective determination of thyroxine enantiomers by ligand-exchange CE with UV absorbance and ICP-MS detectionELECTROPHORESIS, Issue 10 2009Jianzhen Kang Abstract A simple CE method has been developed for the separation and determination of thyroxine (T4) enantiomers in pharmaceutical formulations. The method was based on ligand-exchange mechanism using a Cu(II)/L -proline complex as chiral selector. The effects of different parameters affecting separation such as chiral selector concentration, organic additive, buffer pH and temperature were investigated. A baseline separation of the two enantiomers was obtained at a Cu(II)/L -proline ratio of 1:8 in a borate buffer (15,mmol/L, pH 9.6) containing 10%,v/v acetonitrile. Under the optimized conditions, precision linearity range and detection limits of the developed enantioselective CE method were evaluated and compared using two different detection systems: conventional UV detection at 226,nm and iodine (127I)specific detection ("chiral speciation") with ICP-MS. Both methodologies show adequate analytical performance characteristics with detection limits around 0.30,,g/mL for each enantiomer of T4. Finally, a levothroid pharmaceutical formulation sample was successfully analyzed using both developed methods CE-UV and CE-ICP-MS. [source] Preparation and characterization of C16 monolithic columns for capillary electrochromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 3 2005Kai Zhang Abstract A series of methacrylamide-based C16 monolithic columns were prepared and characterized to determine how their porous structural properties and chromatographic behavior are affected by the percentages of functional monomer, base monomer, and cross-linker in the polymerization solution. Baseline separation of 6 neutral compounds can be readily obtained in an optimized column. Furthermore, the effects of organic additive in the mobile phase, operating voltages, and temperature on retention behaviors and separation efficiencies were also studied. The separation mechanism is also discussed. High column efficiency and good reproducibility indicate that the monolithic columns hold considerable promise. [source] Determination of dissociation constants of ten alkaloids by capillary zone electrophoresisJOURNAL OF SEPARATION SCIENCE, JSS, Issue 6-7 2003Suxuan Gong Abstract The dissociation constants of ten alkaloids, berbamine, (+)-tetrandrine, thalifaretine, thalifaricine, northaltive, matrine, sophocarpine, sophoridine, oxymatrine, and oxysophocarpine isolated from herbal medicines Thalictrum and Sophoraflavescens, were determined by capillary zone electrophoresis (CZE). The analysis time for each alkaloid was within 10 min under the following experimental conditions: acetate (pH 3.81,5.55) and phosphate buffer (pH 6.05,9.29) with ionic strength set at 0.03, applied voltage 30 kV, UV detection at 210 nm, capillary temperature 25°C. Effective mobility for each alkaloid and corresponding pH were fitted to an equilibrium expression by using nonlinear regression as well as linear regression, showing that the two models give comparable results for all studied alkaloids. The correlation coefficients were between 0.987 and 1.00 in the linear regression model, and between 0.978 and 1.00 in the nonlinear model. The measured pKa values for the ten alkaloids were from 5.7 to 7.8. The pKa values changed with the addition of organic additive to the buffer system. [source] Corrosion of ZrB2 Powder During Wet Processing , Analysis and ControlJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2008Sea-Hoon Lee Corrosion behavior of ZrB2 powder during wet processing in water or ethyl alcohol was studied both with and without an organic additive. Incorporation of oxygen and pH change did not intensively occur during static aging of aqueous slurries, but corrosion was enhanced when stirring the slurries. The oxygen content of the powder increased rather rapidly with milling time in ethyl alcohol. The molecular weight of polyethylenimine effected the pH change and oxygen content of ZrB2 powder, after corrosion in water for 18 months. X-ray photoelectron spectroscopy analysis informed that the surface of both the pristine and corroded powders was mainly covered with ZrOH, but a certain amount of Zr,B bonding remained at the powder surface after the wet processing. [source] Synthesis of mesoporous alumina,titania membranes by the sol-gel methodASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2010A. Bottino Abstract Ceramic tubular membranes with alumina,titania top layers were prepared using the dipping procedure and a mixed sol composed of both boehmite and titania. The influence of the Ti/Al ratio, the amount of an organic additive (namely hydroxypropylcellulose), the dip-time, the number of depositions and drying,calcination conditions on the membrane morphology and transport properties were investigated. The conditions for the formation of a defect-free and homogeneous top layer were individuated. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Tape Casting of Graphite Material: A New Electrochemical SensorELECTROANALYSIS, Issue 16 2006M. Chicharro Abstract Tape casting is a feasible method for preparing ceramic tapes with different electrical and magnetic properties for multilayer ceramic devices. This paper describes the tape casting process for the preparation of a new kind of self-standing carbon electrodes (SSCE) using different ratios of graphite and the organic additives generally used in the non-aqueous tape casting process. [source] Tape Casting and Dielectric Properties of Zn2Te3O8 -Based Ceramics with an Ultra-Low Sintering TemperatureINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 4 2009Johanna Honkamo The suitability of dielectric ceramics made of zinc tellurate (Zn2Te3O8) and titanium dioxide (TiO2) with an ultra-low sintering temperature (650°C) for tape casting and thus for the multimodule technique with Al electrodes was investigated. The properties of the tape before and after sintering as well as the amount of organic additives for the casting process and a thermal analysis of the tape up to 1000°C are reported. In addition, electrodes on a multilayer module made on stacked tapes were prepared using Al paste and postfiring, followed by relative permittivity and loss tangent measurements to verify the electrical performance of the whole structure. The dielectric properties of the stacked module without any electrodes were also measured. The results show that the composition is well suited for the tape process but extra care should be taken especially with the proper sintering temperature for optimized electrical performance. [source] Capillary electrophoresis with capacitively coupled contactless conductivity detection for low molecular weight organic acids in different samplesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 18 2007Wai Siang Law Abstract CE with capacitively coupled contactless conductivity detection (CE-C4D) was explored and validated for the identification and quantification of organic acids in various types of samples. The analyses were performed under optimized conditions, using a buffer system composed of 20 mM MES-histidine (His), pH 6.0, 0.1 mM CTAB, 0.025% HP-,-CD, and 10% methanol. The investigation included a study of the effects of buffer pH, concentration of CTAB, type and concentration of organic additives, on the migration behavior, resolution and selectivity of the organic acids. The intra- and interday RSDs (n = 6) obtained for migration time and peak area were typically in the range of 0.12,2% and 0.5,4%, respectively. Linearity, detection limits, and repeatability were evaluated. In order to evaluate the application potential of the developed method, real samples from different sources were analyzed. The results demonstrate that CE-C4D is a versatile tool for analyzing organic acids in beverages, Chinese herbal medicines (CHM) and plants as it allows for their detection, identification, and quantification. [source] Indirect laser-induced fluorescence detection of diuretics separated by capillary electrophoresisJOURNAL OF SEPARATION SCIENCE, JSS, Issue 5 2006Xiuhan Yang Abstract Indirect LIF detection was applied to the detection of four acidic diuretics separated by CZE. Semiconductor laser was employed to provide the stable excitation of 473 nm. With an optimized electrophoretic buffer system which contained 5 mM of triethylamine, 0.1 ,M of fluorescein, and 5% of n -butanol, fast separation of four diuretics (ethacrynic acid, chlorthalidone, bendroflumethiazide, and bumetanide) can be performed within 3 min with the detection limits of 0.2,2 ,g/mL. The impacts of buffer components including the concentrations of the electrolytes, fluorescence probe, and the organic additives were demonstrated. The method was applied for the detection of diuretics in urine. As an alternative way for the fast analysis of diuretics, this indirect detection method provided the technical support for future microchip performances, in which diuretics may be detected in the microchip by the common LIF detector without derivatization. [source] Effect of organic additives on formation and structure of polyelectrolyte-oppositely charged surfactant complexes,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 11-12 2006J. A. Zakharova Abstract Effect of butanol and Triton X-100 on formation, supramolecular organization and local dynamics of poly(N -ethyl-4-vinylpyridinium)-dodecyl sulfate complexes have been studied by UV spectroscopy, high-speed sedimentation, laser light scattering and electron spin resonance (ESR) spectroscopy. It was found that solubilization of butanol promotes aggregation of the complex species in solution and results in contraction of the region in which water-soluble complexes are formed. On the contrary, highly aggregated complexes disaggregate up to molecularly dispersed state upon addition of Triton X-100. It was found that under the experimental conditions neither butanol (up to 3,wt%) nor Triton X-100 ([Triton X-100]/[sodium dodecylsulfate],,,1:1) cause destruction of the complexes. The results of ESR spin probe and spin label studies show that in both cases supramolecular realignments are accompanied by a slight increase of the local molecular mobility of surfactant ions in the complex micelles, segmental mobility of polyelectrolyte being unchanged. Copyright © 2006 John Wiley & Sons, Ltd. [source] Gas,liquid mass transfer in three-phase inverse fluidized bed reactor with Newtonian and non-Newtonian fluidsASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2010V. Sivasubramanian Abstract Liquid-phase volumetric mass transfer coefficients, kLa were determined in three-phase inverse fluidized beds of low-density polyethylene (LDPE) and polypropylene (PP) spheres fluidized by a countercurrent flow of air and Newtonian (water and glycerol solutions) or non-Newtonian liquids [carboxy methyl cellulose (CMC) solutions]. The effects of liquid and gas velocities, particle size, solid loading and addition of organic additives (glycerol and CMC) on the volumetric mass transfer coefficient, kLa were determined. The superficial liquid velocity had a weak effect on the mass transfer whereas the gas flow rate affected the mass transfer positively. kLa increased with increase in particle diameter and decreased with increase in initial bed height (solid loading). kLa decreased as the concentration of glycerol (viscosity) and CMC increased. Empirical correlations are presented to predict the gas,liquid volumetric mass transfer coefficient in terms of operating variables. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] | |||||||||||||