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Electrolyte Composition (electrolyte + composition)
Selected AbstractsNovel Sensitive Voltammetric Detection of Trace Gallium(III) with Presence of Catechol Using Mercury Film Silver Based ElectrodeELECTROANALYSIS, Issue 16 2009Robert Piech Abstract A new adsorptive stripping voltammetric method for the determination of trace gallium(III) based on the adsorption of gallium(III)-catechol complex on the cyclic renewable mercury film silver based electrode (Hg(Ag)FE) is presented. The effects of various factors such as: preconcentration potential and time, pulse height, step potential and supporting electrolyte composition are optimized. The calibration graph is linear from 2,nM (0.14,,g L,1) to 100,nM (6.97,,g L,1) for a preconcentration time of 30,s, with correlation coefficient of 0.9993. For a Hg(Ag)FE with a surface area of 9.7,mm2 the detection limit for a preconcentration time of 90,s is as low as 7,ng L,1. The repeatability of the method at a concentration level of the analyte as low as 0.05,,g L,1, expressed as RSD is 3.6% (n=5). The proposed method was successfully applied by studying the natural samples and simultaneous recovery of Ga(III) from spiked water and sediment samples. [source] Renewable Copper and Silver Amalgam Film Electrodes of Prolonged Application for the Determination of Elemental Sulfur Using Stripping VoltammetryELECTROANALYSIS, Issue 7 2008Robert Piech Abstract New, renewable copper (Hg(Cu)FE) and silver (Hg(Ag)FE) based amalgam film electrodes applied for the determination of elemental sulfur using differential pulse cathodic stripping voltammetry are presented. With surface areas adjustable from 1 to 12,mm2, both electrodes are characterized by very good surface reproducibility (,2%) and long-term stability (a few thousand measurement cycles). The mechanical refreshing of the amalgam film takes about 1,2 seconds. The effects of various factors such as instrumental parameters and the supporting electrolyte composition were optimized. Interferences from sulfides are easily removed by the addition of acid, and bubbling with argon, for Hg(Ag)FE. In the case of Hg(Cu)FE, sulfides did not interfere. The calibration graph is linear within the studied range from 16,ng L,1 to 4.8,,g L,1 for Hg(Cu)FE, and up to 6.4,,g L,1 for Hg(Ag)FE (tacc=15,s). The correlation coefficients for the two electrodes were at least 0.997. The detection limits for a low concentration of S(0) and tacc=60,s are as low as 14,ng L,1 for Hg(Cu)FE and 4,ng L,1 for Hg(Ag)FE. The proposed method was successfully applied and validated by studying the recovery of S(0) from spiked river water. [source] Electron Transfer Kinetics of Ferrocene at Microcrystalline Boron-Doped Diamond Electrodes: Effect of Solvent and ElectrolyteELECTROANALYSIS, Issue 4 2003Shannon Haymond Abstract Cyclic voltammetric measurements were made using well-characterized microcrystalline boron-doped diamond thin-film electrodes to test the material's responsiveness for ferrocene as a function of scan rate, solvent, and electrolyte composition. Apparent heterogeneous electron transfer rate constants, k°app, of 0.042±0.015, 0.048±0.015, and 0.008±0.002,cm/s were observed in 0.1,M NaClO4/CH3CN, 0.1,M TBAClO4/CH3CN, and 0.1M TBAClO4/CH2Cl2, respectively. These rate constants, obtained using electrodes without any type of pretreatment, are similar to those observed for freshly polished glassy carbon. The results demonstrate that boron-doped diamond is a viable material for the electrochemical analysis of nonaqueous analytes. [source] Integrated microdevice for preconcentration and separation of a wide variety of compounds by electrochromatographyELECTROPHORESIS, Issue 3 2009Gaelle Proczek Abstract An integrated microdevice was developed to couple on-chip SPE to separation by channel electrochromatography. An acrylate-based monolith was synthesized within a glass microdevice by photoinitiated polymerization. It was used for both separation and preconcentration by direct injection on the head of the stationary phase or by confining the preconcentration step in a given zone of the stationary phase. The composition of the polymerization mixture was chosen to achieve a monolithic material containing both hydrophobic and charged moieties to ensure an electroosmotic flow for separation. As a consequence the extraction procedure occurs via hydrophobic and ionic interactions. Neutral, ionizable and charged compounds were successfully preconcentrated and separated within the microdevice through electrochromatographic mechanisms, highlighting the versatility of this device. The performance of the integrated microdevice was demonstrated with the preconcentration and separation of a mixture of PAHs for which a signal enhancement factor (SEF) of 270 was achieved within 120,s of preconcentration. In the case of charged and ionizable compounds, according to the electrolyte composition, contributions of both reverse-phase and ion-exchange mechanisms were used to perform effective electrochromatographic preconcentration. A SEF of 250 was obtained for the model-charged compound within 20,s of preconcentration. Finally, the potentials of on-chip preconcentrate and separate both neutral and ionized compounds have been demonstrated using a mixture of model compounds. [source] CEC separation of heterocyclic amines using methacrylate monolithic columnsELECTROPHORESIS, Issue 11 2007Elena Barceló-Barrachina Abstract Two methacrylate-based monolithic columns, one with a negatively charged group (sulfonic group) and another with a new monomer N,N -dimethylamino ethyl acrylate (DMAEA), were prepared and tested for the separation of basic compounds by CEC. This new monolithic stationary phase was prepared by the in situ polymerization of DMAEA with butyl methacrylate and ethylene dimethacrylate, using a ternary porogenic solvent consisting of water, 1-propanol and 1,4-butanediol. The performance of this column was evaluated by means of the analysis of a family of heterocyclic amines. Separation conditions such as pH, amount of organic modifier, ionic strength and elution mode (normal or counterdirectional flow) were studied. At the optimal running electrolyte composition, and using the counterdirectional mode, symmetrical electrochromatographic peaks were obtained, with the number of theoretical plates up to 30,000 and a good resolution between closely related peaks. The 2-acrylamido-2-methyl-1-propane-sulfonic acid column was used for CEC-MS, taking advantage of the compatibility of its elution mode (normal flow) with the MS coupling. [source] Separation of phenolic acids by capillary electrophoresis with indirect contactless conductometric detectionELECTROPHORESIS, Issue 7 2006Petr Kubá Abstract A new method for the electrophoretic separation of nine phenolic acids (derivatives of benzoic and cinnamic acids) with contactless conductometric detection is presented. Based on theoretical calculations, in which the mobility of the electrolyte co- and counterions and mobility of analytes are taken into consideration, the electrolyte composition and detection mode was selected. This approach was found to be especially valuable for optimization of the electrolyte composition for the separation of analytes having medium mobility. Indirect conductometric detection mode was superior to the direct mode as predicted theoretically. The best performance was achieved with 150,mM 2-amino-2-methylpropanol electrolyte at pH,11.6. The separation was carried out in a counter-electroosmotic mode and completed in less than 6,min. The LODs achieved were about 2.3,3.3,,M and could be further improved to 0.12,0.17,,M by using a sample stacking procedure. The method compares well to the UV-Vis detection. [source] Methods for determining labile cadmium and zinc in soilEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2000S. D. Young Summary Isotopically exchangeable cadmium and zinc (,E values') were measured on soils historically contaminated by sewage sludge and ones on zinc-rich mine spoil. The E -value assay involves determining the distribution of an added metal isotope, e.g. 109Cd, between the solid and solution phases of a soil suspension. The E values for both metals were found to be robust to changes in the position of the metal solid,solution equilibrium, even though the concentration of dissolved metal varied substantially with electrolyte composition and soil:solution ratio. Concentration of labile metal was also invariant over isotope equilibration times of 2,6 days. The use of a submicron filtration procedure, in addition to centrifuging at 2200 g, proved unnecessary if 0.1 m Ca electrolyte was used to suspend the soils. The proportion of ,fixed' metal, in non-labile forms, apparently increased with increasing pH, although there was considerable variation in both sets of contaminated soil. Zinc and cadmium in the sludged soils were similarly labile. Several possible methods for the measurement of chemically reactive metal were explored for comparison with E values, including single extraction with 1 m CaCl2 and a ,pool depletion' (PD) method. The latter involves comparing solid,solution metal equilibria in two electrolytes with differing degrees of (solution) complex formation, 0.1 m Ca(NO3)2 and CaCl2. Both the single extraction and the PD method gave good estimates of E value for Cd, although the single extraction was more consistent. Neither technique was a useful substitute for determining labile Zn, because of weak chloro-complexation of Zn2+. We therefore suggest that 1 m CaCl2 extraction of Cd alone be used as an alternative to E values to avoid the inconvenience of isotopic dilution procedures. [source] Template Deformation-Tailored ZnO Nanorod/Nanowire Arrays: Full Growth Control and Optimization of Field-EmissionADVANCED FUNCTIONAL MATERIALS, Issue 19 2009Haibo Zeng Abstract Here, a facile and effective route toward full control of vertical ZnO nanorod (NR)/nanowire (NW) arrays in centimeter-scale areas and considerable improvement of field-emission (FE) performance is reported. Controlled deformation of colloidal crystal monolayer templates is introduced by heating near glass-transition temperature. The NR/NW density, uniformity, and tapering were all adjusted through selection of template size and deformation, and electrolyte composition. In line with the adjustments, the field-emission performance of the arrays is significantly improved. A low turn-on electric field of 1.8,V µm,1, a field-enhancement factor of up to 5,750, and an emitting current density of up to 2.5,mA cm,2 were obtained. These improved parameters would benefit their potential application in cold-cathode-based electronics. [source] A promising method for electrodeposition of aluminium on stainless steel in ionic liquidAICHE JOURNAL, Issue 3 2009Guikuan Yue Abstract A promising method for aluminium deposition was proposed by using AlCl3/[bmim]Cl (1-butyl-3-methylimidazolium chloride) ionic liquid as electrolyte. By using this novel method, the volatile and flammable organic solvent systems and the high corrosive inorganic molten salts with high temperature can be substituted, and the deposit microstructure can be easily adjusted by changing the current density, temperature and electrolyte composition. The study was performed by means of galvano-static electrolysis and the optimum operating conditions were determined based on the systematic studies of the effects of current density, temperature, molar ratio of AlCl3 to [bmim]Cl, stirring speed and deposition time on the quality of deposited coatings. The electrical conductivities of electrolytes were also investigated as a function of temperature (298,358 K) and molar ratio of AlCl3 to [bmim]Cl (from 0.1:1 to 2.0:1). Dense, bright and adherent aluminium coatings were obtained over a wide range of temperature (298,348 K), current densities (8,44 mA/cm2) and molar ratio (1.6:1,2.0:1). Results from the analysis of crystal structure show that all of the electrodeposits exhibit a preferred (200) crystallographic orientation. Temperature has significant influence on the crystallographic orientation and there does not appear to be an apparent impact of current density on it. Analyses of the chronoamperograms indicate that the deposition process of aluminium on stainless steel was controlled by three-dimension nucleation with diffusion-controlled growth and there is a conversion from progressive nucleation to instantaneous nucleation. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] HPLC of humic substances fractionated by Flow FFFJOURNAL OF SEPARATION SCIENCE, JSS, Issue 5 2003Maria-Anna Benincasa Abstract This communication reports a study of the effect of ionic strength and electrolyte composition on fractions, separately collected by flow FFF, of a mixture of humic substances. Reverse phase HPLC analysis of three early eluting fractions suggests that the components released by the column behave as organic acids. The baseline-resolved peaks of the first two fractions, subject to higher retention in solutions of lower pH and/or higher polarity, substantiate this suggestion. The fraction with larger components, as measured by flow FFF, also appears to contain acidic species. Their retention level, however, may not be accurately modulated by varying the mobile phase properties as these species are either totally retained in acidic phases or released before the void peak at pH , 4.2. Besides showing the effective separation achieved in the flow FFF channel, this study reveals the pronounced difference in the physicochemical properties of some components of a humic mixture even with very close particle size. [source] Investigation of p-type macroporous silicon formationPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2005C. Lévy-Clément Abstract Nanopores and macropores can be formed electrochemically on p-type silicon depending on the silicon resistivity and composition of the electrolyte. In order to understand if the structural dimensionality of the porous p-type Si, either nanopore or macropore formation, depends on the electrochemical process at the Si/electrolyte interface, in situ pulsed surface photovoltage (SPV) and photoluminescence (PL) measurements have been undertaken. The SPV and PL studies have been made as a function of the applied current density as well as the electrolyte composition (aqueous or in presence of organic solvent) and the silicon doping density. Main results show that the Si surface is well passivated with preferential formation of ionic species and the Si band bending is around 100 mV, during porous Si formation. It varies slightly with the doping density, but is not affected by the composition of the electrolyte (HF/water and HF/organic solvent). This demonstrates that the chemistry of the electrolyte plays a major role in the formation of macroporous and nanoporous Si, but has still to be determined. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] New interdigital design for large area dye solar modules using a lead-free glass frit sealingPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 8 2006R. Sastrawan Abstract A new interdigital design for large area dye solar modules is developed for an area of 30×30,cm2. This design requires fewer holes in the glass substrate for electrolyte filling, than the conventional strip design. A complete manufacturing process of this module,ranging from screen printed layers to semi-automated colouring and electrolyte filling,in a laboratory-scale baseline is illustrated. As primary sealing method, a durable glass frit sealing is used. It is shown, that the lead (Pb) content present in many glass frit powders contaminates the catalytic platinum electrode during the sintering process, resulting in a lowering of the fill factor. A screen printable lead-free glass frit paste is developed, which solves this problem. Long term stability tests are presented on 2·5,cm2 dye solar cells, which have been completely sealed with glass frit. In consecutively performed accelerated ageing tests under 85°C in the dark (about 1400,h) and continuous illumination with visible light (1 sun, about 1700,h), a 2·5,cm2 dye solar cell with an electrolyte based on propylmethylimidazolium iodide showed an overall degradation of less than 5% in conversion efficiency. In a subsequently performed thermal cycling test (,40°C to +85°C, 50 cycles) a 2·5,cm2 dye solar cell with the same electrolyte composition also showed only a slight degradation of less than 5% in conversion efficiency. Copyright © 2006 John Wiley & Sons, Ltd. [source] | ||||||||||